Chesapeake Science Vol. 4, No. 4, pp. 175-191

December, 1963

Sport Fishing Survey of the Lower Potomac Estuary, 1959-1961 CHAI~,LES M. FRISBIE AND DOUGLAS E. RITCIIIE, JR. ABSTRACT A survey of the sport fishery was conducted in a 265-square-mile area of the lower Potomac Estuary during the summer and fall of 1959, 1960, and 1961. Fisherman interviews, postal card questionnaires, and aerial boat counts were used to determine angling pressure, rates of catch, estimated harvest, species importance, and economic value of the sport fishery. Postal responses were increased from 33.5 to 66.3 percent, perhaps minimizing bias from non-response. No important differences were found in 1961 between initial and follow-up postal returns. The 1961 estimate indicated that 101,000 angler trips produced approximately 1,200,000 fish weighing almost 642,000 pounds. Party size averaged 3.0 anglers who fished approximately 4.5 hours per trip and creeled 2.6 fish per man-hour. Virtually no significant differences were found between rates of catch for incomplete and complete trip data in the only year tested--1961. Interview or postal surveys appear equally effective in providing rates of catch and each might be used solely in future surveys. Confidence limits for 1961 revealed narrow ranges for both incomplete and complete trip estimates of fishing pressure and harvest, indicating precise survey methods. Trolling was the more productive fishing method for striped bass and bluefish. Still fishing yielded higher catches of spot, white perch, weakfish, yellow perch and other bottom species. Resident striped bass ranked first in importance to the sport fishery in 1960, primarily due to recruitment of the dominant year-class of 1958. Throughout the survey, fish of age group II dominated the striped bass catch, while striped bass six years and older made up less than six percent. The spot ranked first in the 1961 catch. During the five-month survey in 1961, an estimated $594,000 was spent by Potomac Estuary anglers. The average angler spent $5.80 on each of his 29 mean yearly trips. Introduction l,arge populations of several p o p u l a r fish species and wide expanses of open w a t e r near metropolitan areas have p r o m o t e d the growth of spol~ fishing in Ma~:cland's tidal waters. S u r v e y s b y T r u i t t and V l a d y k o v (1937), T r u i t t (1938), Buzzell and W a l k e r (1954), Plosila (1961), and Shearer, Ritchie aud Frisbie (1962) pointed o u t the importance of tidewater angling. A l t h o u g h commercial fishelT statistics have long been available for legislative and m a n a g e m e n t use, there has been a lack of accurate d a t a on the tidewater sport fishery in M a r y l a n d . Scientific r e c o m m e n d a t i o n s for the m a n a g e ~Contribution No. 250, Natural Resources Institute of the University of Maryland, Chesapeake Biological Laboratory, Solomons, Maryland.

m e n t of the fishery have been prevented by this void. T h e portion of the l ' o t o m a c surveyed, while an impol~ant sport fishing area, is also a productive commercial fishing area. It yielded an average of 1,150,000 pounds (range 721,000 to 1,530,000 lbs) of striped bass for the five years 1958-1962 ( I B M runs plus delinquent raw d a t a from Fishery Statistical Section, N a t u r a l Resources Institute, Univel~ity of M a r y l a n d ) . This s t u d y was initiated: (1) to estimate intensity of angling pressmv, catch per unit effort, angling hax~ests and importance of striped bass and other species; (2) to improve tidewater creel census techniques for striped bass; (3) to provide information for m a n a g e m e n t and legislative use; (4) to acquire biological d a t a on "mgler-eaught

175

176

c.M.

FRISBIE AND D. E. I~ITCHIE~ JR.

TA~L~ 1.--Species of fishes ranked by importance in the angler's catch in the Potomac Estuary, 1959-

1961. Rank CommonName

ScientificXame

1

Spot

2

WhitePerch Roccus america-

Leiostomus xanthurus

Striped bass' Rocc.us saxatilis

4

Weakfish

Cynoscion regalis

5

Bluefish

Pomatomus saltatrix

Yellow Perch American Eel

9

10 11

BiologicalAspeers

Norfolkspot; spots; Lafayette

Summer migrant from ocean, resident from May-October; bottom feeder; usually abundant. Resident; migratory in river in spring; predatory, mostly on bottom; very abundant. Resident; migratory; predatory, from bottom to surface waters; abundant. Summer migrant from ocean; resident from June to October; abundance fluctuates. Summer migrant from ocean; resident

Perch; white perch; black perch

nus

3

Local Names

Rock; rockfish; striper Trout; sea trout; gray sea trout Blues; snappers; !

tailors

Yellowned; ring perch; rainbow perch Anguilla rostrata Eel

Perca flavescens

Atlantic Croaker

Micropogon undulatus

Croaker; ha.rdhe~d

White Catfish Summer Flounder Toadfish

Ictalurus caius

Catfish; white cats

Paralichthys dentatus Opsanus tau

Flounder; fluke Toad; oyster toad

striped bass; (5) to evaluate the methods of fishing and types of boats u ~ d ; and (6) to assess the economic value of the lower Potomac Estuary sport fishery. This project is part of a cooper~tive s t r i ~ d bass investigation currently being conducted by the Natural Resources Institute of tile University of Maryland and the U. S. Bureau of CommerciM Fisheries. Aeknowledgments:--Appreciation is gratefully extended to the late, Dr. R. J. Mansueti, who directed tile survey and gave much helpful advice. Dr. Vincent Schultz, of the U. S. Atomic Energy Commission, gave constructive advice on methodology and interpretation of results. Dr. F. J. Schwartz, of the Chesapeake Biological Laboratory, gave welcome assistance in the analysis of data and critically reviewed the manuscript. I)r. R. J. Muncy, of the School of Forestry, Louisiana State University, designed the 1959 sur~'ey, aided by W. Davis, J. F. Sykes, R. B. Chapoton, R. R. Bonner and R. M. Lewis, of the Bureau of

from June-September; predatory. Resident; predatory, from bottom to surface; more common in low saline waters. Resident using tidewater as nursery area; bottom predator and scavenger; common. Summer migrant from ocean; resident May-October; bottom feeder; abundance fluctuates. Resident in lower saline areas; bottom feeder and scavenger. Summer migrant ; bottom predator; uncommon. Resident; bottom scavenger; abundant.

Commercial Fisheries Biological Laboratory, Beaufort, North Carolina. Staff members of the Chesapeake Biological Laboratory assisting were: L. W. Shearer, G. Butz, A. de Kok, W. Dovel, G. Gerberg, W. Hagen, J. IIardy, C. Meyers, Eleanor Ritchie and M. Taylor. D e s c r i p t i o n o f t h e S t u d y Area

The Potomac P~iver southeast of Washington, D. C., is a broad estuarine tributary which separates MaryIand and Virginia and enters the Chesapeake Bay along its midwestern shore. The tidal portion extends 117 miles from Smith Point, Virginia, to Little Falls just above Chain Bridge near the northwest boundary of the District of Columbia. The Potomac River, exceeded only by the Susquehanna River in mean stream flow, contributes about 16 per cent of the total inflow of Chesapeake Bay (Wells, Bailey, and Ilendemon, 1929:109). Salinities at Lower Cedar Point, Charles County, Maryland, range from 5-14 ppt between

SPORT F I S t I I N G SURVEY OF T H E POTOMAC ESTUARY

177

July and late November. The mem~ tidal signed to be a systematic pilot study so that amplitude is approximately 1.5 feet -q- 2 more efficient sampling could be designed in feet (U. S. Coast and Geodetic Survey the following years. Thus, fifteen days were Tide Tables, 1960). Farm land bounding subjectively selected for sampling during the estuary is sparsely settled and dissected August, September, and October. Sample by many small creeks, bays, and rivers which days were staggered throughout tile survey provide extensive harbors, anchorages and 'period. Mondays and Tuesdays comprised launching sites for sport fishermen. Several the first sampling interval, Wednesdays and marinas, small boat liveries, and numerous Thursdays the ~eond, and Fridays, weekends, and holidays the third. Practical probcharter or party boats operate in the area. The species composition of the angler's lems during the short survey period prevented eatc.h varies daily and is governed by: (1) total harvest estimates from being made. In 1959 a single observer in a small runthe influx of migraut species which spend the wanner months feeding in the Potomac; about interviewed fishemaen in Area III, (2) the spawning runs of resident species; collecting data on time spent fishing, catch, and (3) the presence of dominant year- baits, methods, and type of boat. He also classes of both migratory and resident fishes left postal cards asking that they supply (Table 1). Still fishing anglers are likely to information on their day's trip at its comcatch spot, white perch, weakfish, yellow pletion. The boat obsetwer made morning perch, eels, croakers, and other species. and afternoon runs over the area trying to Trolling anglers catch mainly striped bass contact all parties fishing. The 1960 and 1!)61 surveys (July through and bluetish. Still fishing and trolling methods are described and defined by Shearer, November) were conducted solely by the Natural Resources Institute of the Uniet al. (1962:4). versity of Maryland. Area III remained Methods the important test srea for 1960 and 1961. Area division:----The lower 96 miles of To insure representative samples, the samthe Potomac Estuary was divided into five pling system was changed t,o a stratified study areas (1959.1901) to facilitate aerial random one as suggested by Calhoun boat counting: Area t, comprising approxi- (1950 :192-6) , Rounsefell and Everhart mately 89 square miles, extended from (1953:76-7), and ,lessen (1956:50-6). WeekSmith Point, Virginia, to Point Lookout, days and weekends were stratified and the Maryland, and upriver to Piney Point, sample days were selected randomly (SnedeMaryland; Area Ii (83 sq. mi.), from Area I cor, 1956). This change was necessary to upriver to the upper end of Cobb Island, estimate the total angler catch. Sample Maryland; Area III (35 sq. mi.), the u p ~ r days in 1960 and 1961 were, treated as end of Cobb Island to U. S. Rt. 301 Potomac representative of their respective weeks or River Bridge; Area IV (58 sq. mi.), from weekends. For increa~d efficiency, a larger survey the Potomac River Bridge to Sandy Point, Mm3dand, and across to Quantico, Virginia; boat (16 ft.), and both an operator and an Area V (34 sq. mi.), from Quantico to the interviewer, were used in the 1960 and 1961 Jones Point Bridge at Alexandria, Virginia. surveys. The schedule of two boat trips per Area IiI was studied intensively since it day was maintained and data on all species was considered to be productive and was were obtained. Each fishing party was given easily accessible to striped bass anglers and a self-addressed postal card asking for more detailed information than the 1.959 card. survey persom~el. The 46 square miles surveyed in 1959 These were to be completed at the end of (Area III) was reduced to about 35 square the fishing trip. Frequently (in 1960), the miles in 1960 to speed up the boat observer's interviewer recorded the residence of anglers. In 1961 some minor changes were intrips and since light fishing pressure had been observed in the lower reaches (Fig. 1). corporated into the sampling methods. Sampling:---The 1959 study was de- Areas I, 1[, IV, and V were qualitatively

178

FRISBIE AND D. E. RITCHIE) JR.

c.M.

I chesapeake Bay

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.

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TIDEWATER

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e

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~"

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-:;.

:'2". ~ } ! . \ 4 ~ ' ; ":: :':'" - 9

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x.y

~

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RIVER

SURVEY AREA i

.

"',

POTOMAC

"2: ~

r

-!

~

~ ~ b c , 6~~ . . . ~ . , , ~ 'if *'*~'-

...- " : .','2 - 2":......

MARYLAND "'.1! ., ~~I R YC hCounty a r l e:";::(:~' s

~:

:.'. ,.':'.

:'-" :['~.:.

%1"~21('2 "'7::

:,

9-

'..". i...:.,:.....

..:....,...

.

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9 I .::..

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Upper Machodoc Creek

/

~i 9

/

Colonial BeachL'Z::,.

..':'~"

'~

/

/

/

//

:::

-::

/

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/

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Monroe Creek

VIRGINIA County

%estn~oreland

o

l

2

9~:2]~)""

:~

r176 '

Fig. 1.--Location of Area III, the most intensely studied area, in relation to the remainder of the lower Potomac River Estuary. surveyed periodically by the boat observers, employing essentially the same techniques as in Area III. These "spot cheeks" were used to detelanine the intra-area relation-

ships trod to help evaluate the whole fishery. The boat survey pattern for the other areas was determined by monthly a n a l y ~ s of 1960 aerial counts of fishing boats. The

SPORT FISHING SURVEY OF THE POTOMAC ESTUARY

number of sampling days per month per area was determined by the monthly percentage of angling pressure within that area. These "spot sampling" days were assigned randomly. it was considered desirable to scud "follow-up" letters to postal card nonrespondents in 1961. The authors felt that better interview response would result if anglers were not asked their names and addresses. Since Maryland does not require licenses for tidewater angling, angler identities were determined by recording their boat license numbers. Aerial flights:--On the survey days in 1959, morning and afternoon aerial surveys permitted a count of fishing boats (skiffs, runabouts, private cruisers, and party boats), the number of fishermen per boat (under favorable conditions), and the method of fishing-~ither still or trolling. Only one plane flight per day was possible in 1960 and 1961. This covered the area between the mouth of the river at Point Lookout, Maryland, and the Jones Point Bridge at Alexandria, Virginia. Fishing boats were counted and categoriT~ed by type and method of fishing, in order to measure angling pressure in the survey area as well as in other areas of the estuary. Flight schedules were adjusted so that angling parties (boats) were counted at approximately the time when boat interviews arid counts were made, either in the morning or afternoon. Choices of morning or afternoon flights were randomly selec~d. In 1960 postM replies suggested that a single aerial count at 0800 or 1300 hours would include about half the boats fishing in the study arcs during the entire day. Postal replies indicated that the average fishing trip length was 4.7 hours, roughly coinciding with tidal changes in the early morning or late afternoon. Preliminary data were subjected to a " t " test to determine if there were significant differences in the mean numbers of boats fishing, those counted by boat observer (morning and afternoon total) and plane counts (doubled). No significant differences existed at either the one (P = 2.86) or five per cent (P = 2.09) probability levels at 19 degrees of freedom (t = - 1.08). This agr~s with Elser (1960:42) who de-

179

termined that 40 and 45 per cent of the day's fishermen in Maryland were counted at 10:00 a.m. and 2:00 p.m., respectively. "lnterviewers:--Anglers in 1960 and 1961 were contacted by interview personnel who recorded type of boat, fishing method, number of fishermen, bait used, catch, and number of hours fished. Since they were actively fishing when interviewed, the anglers' responses were considered as incomplete trip data and are used in this manner throughout this study. When interviewed, anglers were given a postal card asking for information on that day's fishing success and a,ssociated trip data. P~eturned postal cards were, therefore, the basis for complete trip data. Specifically, the cards asked how many hours were fished and the number of striped bass caught, kept or returned. Although adverse weather and heavy fishing pressure were sometimes encountered, a~l effort was made on the two daily survey circuits to contact all fishermen. During each sample day, dockside observers interviewed returning fishermen, collected completed postal cards, and obtained biological data on the catch. Observers were situated at commercial liveries at Morgantown and Cobb Island, Maryland, and at Colonial and Potomac Beaches, Virginia. $~shing pressure:--Fishing pressure in 1961 was markedly different from that in 1960. Preliminary analysis of boat counts versus plane counts indicated that the 1960 system, using doubled plane counts for pressure estimates, could not be used. Monthly pressure curves were constructed, using data from postal ca~t returns wherein the anglers reported the hours fished. Plane counts were compared with the pressure curve (percent daily pressure) at the time of the aerial observation. This method produced factors which were used to estimate the total effort. Economic aspects:--An effort to weigh the economic aspects of the sport fishery of the tidewater Potomac was added in 1961. Self-addre~cd postal cards were given to anglers, asking them to list their day's expenses for boat-gas, oil, bait, rent, food, refreshments and trivia. They were asked how much of the above was spent near the

180

c.M.

FRISBIE AND

river and how much near their homes. Total cost of equipment, number of miles traveled, and number of trips per year were also reques~d. Weekly estimates:-.Estimated weekly catches of striped bass and other species were derived by the following formula: Estimated weekly catch for boat type t = 5BtI{t + 2bt[(rt -J- r~t)/2]

Where Bt = doubled plane count for each boat type t for the weekday sampled (in 1961 surface counts were multiplied by factors derived from plane counts at a specified time on the pressure curves) R~= Weekday rate of catch for boat type t bt = Saturday and Sunday plane counts for type t r t = Saturday rate of catch for boat type t rlt= Sunday rate of catch for boat type t Average weekend rate of catch for boat type t = [(r~ + dt)/2] 5 = Number of weekdays per week. Estimates for partial weeks at the begiiming or end of a month were derived by averaging data from the last. complete week of the preceding month with the first full week of the following and prorating the estimate for the number of days occurring in each month. Total annual estimates:---Total harvest estimates were not possiblc in 1959 because of the limited scope, of the survey. Daily tabulations of data produced rates of catch of striped bass, number and percentages of boat types used, and number of anglers using different angling methods during the limited period within survey A ~ a III. Total harvest estimates in 1960 and 1961 were simply summations of weekly and monthly estimates. Separate estimates were made for still fishing and trolling and for incomplete and complete, trips. Fish poundage estimates:--The weights of striped bass were calculated from postal card data wherein anglers reported their catch in size. groups of 12-14 inches, 14-17 inches, and t7 inches to 15 pounds. Percentages of each group were determined

D.

E. RITCIIIE, JR.

and con'esponding weights derived from biological sampling were applied in data expansion. Average weights of other species were extrapolated from Hildebrand and Schroeder (1928). Mean weights used in the poundage expansion were as follows: striped ba.ss--12 to 14 inches--l.2 pounds, 14 to 17 inches--2.1 pounds, 17 inches to 15 pounds--5.8 pounds; bluefish--l.4 pounds; white perch--0.3 pounds; spot--0.4 pounds; croaker--0.9 pounds; weakfish---0.6 pounds; yellow perch ---0.3 pounds; eels---1.0 pounds; white catfish--l.5 pounds; summer flounder--l.6 pounds; and toadfish--0.5 pounds. Results and D i s c u s s i o n VALIDITY OF SAMPLING METHOD

The validity of the sampling scheme used for ~he Potomac in 1961 was discussed by Shearer, ct al. (1962:6-9) in a similar study in the Patuxent Estuary. Two types of data, incomplete and complete, have been used for the harvest and pressure expansion in an effort to improve census techniques. A basic question was whether one set of data, either complete or incomplete, was sufficient to show a realistic pictu~ of the sport fishery. Jcssen (1956:55-6) listed two mssumptions necessary to equate incomplete and complete data: (1) the rate of catch must be the same, before and after the interview; and (2) the catch-per-unit-effort cannot be different between the two groups. Since the total fish pet' man-hour rates were not very different, a modified "t-test", as suggested by Di Costanzo (195629), was used to determine any significant differences between catch-effort ratios of incomplete and complete fishing responses. Data from each boat type were grouped by month, method of fishing, and complete or incomplete response. Since only 3 of these 45 tests showed a significant diffei~nce between catch-effort ratios of incomplete and complete data (Table 2), eli,her method alone appears adequate for future tidewater angling surveys. POSTAL RESPONSF, 1959--1961 Postal response was satisfactory throughout the survey. In 1959, of 346 cards given

SPORT

FISHING

SURVEY

OF

THE

POTOMAC

ESTUARY

181

TABIA~2.--T-test data determining the significanceof the differencesbetween catch-effort ratios for incomplete (I) and complete (C) fishing trips made during the 1961 Potomac Estuary Sport Fishing Survey. Test is from Di Costanzo (1956:29). Significance at the 95% level is indicated by *, at the 99.9% level ** Boat T y p e

Month

Method of Fishing

Skiff s c~

July

Still Troll

August

Still Troll

Sept.

Still Troll

Oct.

Still Troll

Nov.

0.80 1.20 0.19 0.40 1.80 1.64 0.69 0.68 2,28 5.44 0.70 4.47 0.34 9.23 0.23 0.48

Runabout t,

48

0.56

12

0.70

51

0.23

27

1.91

61

1.86

Ii

1.18

6

1.15

40

0.96

13

0.56

P0.95

c/e

2.021 0.80 0.70 2.179 0.42 0.51 2.021 3.32 1.04 2.052 0.23 0.15 2.000 2.92 4.98 2.201 0.24 2.76 2.447 0.34 1.43 2.021 0.44 O, 62

Still Troll

0.35 0.79

2.160 0.67 0.49

d.f.

t. valut

Private Cruiser P0.98

c/e

d.f.

2.021 0.40 17 0.30 2.052 0.39 8 0.96 40 1.93 2.021 0.43 14 2.17 : 0.40 2.021 0.36 i3 46 0.20 1.41 2.00 2.40 25 61 1.92 22 1.31 2.074 0.28 29 0.39 0.92 2.365 0.68 6 7 2.00 0 . G 0 1 . 9 8 0 0.82 88 97 0.85 N o Still F i s h i n g O b s e r v e d 0.12 2 . 0 0 0 0 . 6 2 84 0.81

t. vain(

P0.95

2.120 0.40 1.30 2.306 1.14 1.77 2.145 2.21 2.16 2.160 0.94 1.70 2.060 0.38 0.22 2.045 O.OO 1.70 2.447 0.00 0.04 2.000 0.67 1.41

44

0.24

0.24

27

0.20

0.67

out to angler parties, 116 or 33.5 percent were returned. In 1960, of 827 cards distributed, 329 or 40 percent were returned. In 1961, of 828 cards given out, 549 or 66.3 percent were returned giving an overall average return of 49.7 percent. Richards' lower Chesapeake Bay survey (1962:229) attained a 32.7 pereenf average return. Shearer, et M. (1962:6) reported a 35.8 percent return from the Patuxent River. Lower returns from California striped bass anglers were reported by Ryan (1959:95) with 35.0, 36.3, and 32.0 percent; Calhoun (1950:180) with 30.9 percent; and Skinner (1955:32) with a 33.5 percent return. Two factors may be responsible for the higher average postal returns in the Potomac surveys. In 1960 and 1961 the postal cards asked "Are you satisfied with fishing in tidewater?" This presented a chance for angler comment. In 1960, 71.2 percent (234 parties) of those anglers who answered the question were satisfied and 28.8 percent (95) were dissatisfied. In 1961 there were 47.2 percent (259) satisfied and 52.8 percent (290) dissatisfied. The second factor was a "follow-up" letter to non-respondents in 1961. The letters asked the fishermen to complete enclosed postal cards for the days when they

P a r t y Boat

1.30 1.14 1.50 O. 44 0.88 0.09

0.68

c/e

1.9901.281"16

d.f.

value 1P0.98

18

1.36

I 2.101

14

[.31

I 2.146

27

).05

I 2.052

20

t.81

] 2.086

27

L38" ] 2.052

17

1.72"*I 2.11

2

~.80 ] 4.303

48

t.00"*1 2.0t

47

0.27

2.021

were initially interviewed. Of the 339 parties receiving "follow-up" letters and cards, 164 or 48.4 percent responded. Usable returns amounted to 76.2 percent. No important differences were observed between data from the initial and "follow-up" cards. 1959 SURVEY Moderately good catches were revealed by the limited 1959 survey, it was M t that the months chosen would show the transition from moderate fishing success in August, to fMr in September, to good in October for striped bass. Incomplete trips yielded catch rates of 0.26, 0.22 and 0.37 fish per man-hour for August, September, and October, respectively, with an overall average of 0.27 fish per man-hour. Complete trips yielded 0.33, 0.48 and 0.82 fish per man-hour with an overall average of 0.48 fish per man-hour. Possible bias in the reporting of catches was indicated in these data, particularly in September and October. Small boats (skiffs, runabouts) predominated in the area, showing a decline in numbers as the season progressed. Private boats were most numerous in September and used less frequently in October. Numbel~ of party boats were reasonably stable through-

182

C.M.

FRISBIE A N D

TABLE 3.--Numbers and percentages of boattypes used in the striped bass sport fishery in Area III of the Potomac River, 1959.1 August

September

October

Total

Boattypes No.

~kiffs runabouts 'rivate 'arty Totals

%

116 48.3 100 49.0 31 33.7 1434.1

____]

261

No.

%

No.

%

78 67 44 13

32.5 ~2.8 47.8 31.7

46 37 17 14

19.2 18.1 18.5 ,34.1

202

i

No.

%

240 41.q 204 35.4

114

92 15.c~ 41 7.1 577

Actual counts taken on specific sampling days. TABLE4.--Number of fishermen using different methods of angling in the striped bass sport fishery in Area IIl of the Potomac River, 1959.1 Trolling

August September October Totals

Still Fishing

~o_~_. %

No__

311 [38.5 233 I 28.8 264 / 32.7

432

Bank and Pier

%

[63.1

243 l 35.5

2o 685 /100.0

1414 .2 13

4

41.9

12.9

- (110- 0

Actual counts taken on specific sampling days. out the sampling period (Table 3). Inclement weather was an impol~ant factor in determining use. of a specific boat type. Trolling was the most popular method of fishing for striped bass in August and renmined about the same during September and October. Still fishelTnen were more numerous in August but exhibited a continuing decline in numbem during September and October. Bank and pier fishing was relatively unimportant in the fishery (Table 4).

D. E. RITCHIE, JR.

relatively large numbers of pan-sized striped bass was stabilized in 1961; however, the October 1961 catch increa~d when some fast-growing striped bass from the 1960 hatch entered the fishery. Trolling and still fishing rates of catch are compared for Area I I I during 1960 and 1961 (Fig. 3). These data r e p r e ~ n t all species caught and are derived from angler interviews. July was the best mouth for trolling in 1960 with over 100 fish caught per 100 hours fishing. A general decline in rate of catch by trollers began in August and continued, with October yielding a low rate of about 44 fish per 100 hours. The best month for still fishing catches was August, yielding almost 200 fish per 100 hours effort. White perch accounted for almost 80 per cent of this total. Still fishing was generally more productive than trolling, in some cases being more than twice as good. The bulk of the still fisherman's catch was comprised of white perch, spot, eels, and catfish. The rates of catch in Area III changed markedly in 1961 (Fig. 3). November was the nmst productive month for trolling anglers with a catch of about 71 fish per 100 hours, followed elo~ly by July with 63 AREA POTOMAC

"re"

RIVFR

RATES OF CATCH 1959 TO 1961 Rates of catch of striped bass were generally the highest during 1960, followed by 1961 and 1(,)59 (Fig. 2). Data in Fig. 2 is confined to Area I i I and to August-October since the months sampled in 195(,} were limited. These values show the general trend of fishing success in the mid-estuary and are not presented as typical of the entire estuary south of Washington, D.C. The 1(,)58 yearclass of striped bass contributed the most to the larger catches in 1960. The condition of

AUG

SEPT MONTHS

OCT

Fig. 2.--Numbers of striped bass caught per one hundred hours trolling for comparable periods in Area lli of the lower Potomac Estuary. Estimates are based on incomplete trip data.

SPORT

FISHING

SURVEY

OF THE

per 100 hours; the least productive month in 1961 was September. Still fishermen in October 1961 took over 200 fish per 100 hours. Again, whiW~ perch predominated in August,, September and October. Still fishing rates of catch were four times higher than trolling rates in October. Collectively, 1960 Area I[I catch rates were almost double those of ]961 (Table 5). Incomplete trip data indicated 1.34 fish per man-hour in 1960 while complete trips yielded 1.42 fish pet" man-hour. Shearer, et al. (1962:10-11), for the Patuxcnt River in 1960, reported rates of 1.24 (incomplete trip data) and 1.62 fish per man-hour (complete RATE OF CATCH TROLLING VS STILL F I S H I N G I

I

|

I

AREA 3

AUG.

SEPT.

OCT.

NO RATES AVAILABLE

TROLLING j~

NOV.

STILL FISHING

JULY

J

TROLLING ~j

STILL FISHING

AUG.

1961 AREA 3 SEPT.

OCT.

NOV. NO RATESAVAILABLE I

I

I

I

I

50

100

150

200

250

FISH PER HUNDREO

183

ESTUARY

TABLE 5.--Fish per man hour by species, ~trolling

and still fishing combined, Area III, Potomac River, July-November 1960, 1961. 1960

1961

Species Complete

Striped Bass White Perch Bluefish Spot Yellow Perch Eels Toadfish Total all species

lncomplete

Complete

Incomplete

0.48 ;~ 0.71 0.67 I 0.50

0.39

0.30 0.29

0.00

0.00

0.02

0.00

0.9-4 0.01 0.01 0.01

0.12 0.05 0.00 : 0.00 0.01 0.00 0.00 0.00

0.02 0.00 0.00 0.00

7i

0.32

--o.78

o.81

1 Trout and catfish rates in 1961 were less than 0.01 fish per man hour.

I

1960 JULY

POTOMAC

HOURS

Fig. ,%--Comparison of the rates of catch for all species combined, trolling versus still fishing, from Area III of the Lower Potomac Estuary in 1960 and 1961, based on incomplete trip data.

trip data). In contrast, Plosila (1961:57) determined that anglers creeled 0.45 fish per man-hour from the Susquehanna River in 1960. Limited observations on species other than striped bass pointed to a future need for more concentrated evaluation of the sport fishery as a whole, rather than emphasis on a single species. For instance, gray trout, yellow perch and catfish catch rates were low in 1961, but no catfish or gray trout were reported caught in 1960 in Area III. The relationship of these other spec.ies to striped bass may be important, particularly in the role of buffer species. More attention was given these species in the 1960 and 1961 surveys, than in 1959. Trolling rates of catch in Area I I I from all boat types decrea~:d after July 1960. P a r t y boat anglers experienced the greatest decline, yet their catch rates were markedly higher than other types. No important differences were noted in the mean rates of catches for anglers in skiffs, l~nabouts and private cruisers. In 1961 pal~.y boat fishe~znen in Area III produced the highest rates of cat(:h in July and Novemt~n', skiff fishermen caught mol~ fish in August, and private cruiser anglers wel~e more successful in September and October. These rates of catch ranged from a low of 0.18 fish per man-hour for runabout anglers (August) to a high of 1.16 fish per man-hour for party boat fishermen (Novem-

~r).

184

c . M . FRISBIE AND D. E. RITCHIE, JR.

TABLE 6.--Total estimates of sport fishing pressure and harvest of fishes based on angler interviews (incomplete trips) by method of fishing, Areas I-V, Potomac River, July 15 through November, 1960, exclusive of 316 still fishing parties in October for which no rates were available. Estimates were derived using rates from Area III.

Fishing Pressure No. Parties No. Anglers. Avg. Anglers/Party Total Man Hours Avg. Hours/Man Rates of Catch Fish/iV[an-hour Fish/Party Harvest--By Species

Striped Bass Bluefish White Perch Spot Atlantic Croaker Weakfish Yellow Perch American Eels White Catfish Summer Flounder Toadfish

Trolling

Still

Total

11,900 29,300 2.47 74,700 2.55

14,700 42,200 2.87 80,100 1.90

26,600 71,500 2.69 154,800 2.17

0.83

1.59 8.68

1.22 7.13

5.22

No.

Lbs.

61,900 111,000

No.

Lbs.

TotalNo.

%

TotalLbs.

%

1,960

3,100

63,860

33.7

114,100

73:3

~0,000 100,000 8,270 20,700 149 170 106 170 843 2,700 1,180 1,180 1,090 725

52.8 10.9 0.1 0.1 1.4 0.6 0.4

30,000 8,270 149 106 843 1,180 1,090

19.3 5.3 0.1 0.1 0.5 0.7 0.7

189,505 --100.0 -- 155,738

100.0

100,000 20,700 170 170 2,700 1,180 725

Totals Still fishing rates of catch for anglers using all boat types except runabouts were greatest in August of 1960; runabout anglers had their highest rate of catch in July. A decline began in August, extending to October, with skiff anglers noting a small November increase. In 1961, catch rates by boat type were extremely variable, showing no discernible pattern. Values ranged from practically zero for runabout fishermen in October. P a r t y boats were observed still fishing only in August. Apparently when the trolling is productive, no effort is expended still fishing. INCOMPLETE TRIP DATa E s t i m a t e d pressure a n d h a r v e s t - 1960:--These pressure and harvest data wine derived from angler interviews or incomplete trips (Table 6). The total harvest estimates were derived using catch-effort data for Area III, plus pressure data from aerial boat counts of the whole estuary. These ale the best estimates available as no clear relationships were found between fishing pressure and harvest in 1961 for Area

I I I and the remainder of the river (determined with qualitative spot checks of other areas). The estimates are believed to be conservative for the five sampling months, due to a shorter survey (less one-half of July) and since catch=effm~ rates were incomplete. In addition, no bluefish were reported caught in Area I I I in 1960, thus none appear in the estimates. Approximately 29,300 anglers trolled 74,700 hours during 11,900 boat trips and caught about 61,900 striped bass weighing approximately 111,000 pounds (Table 6). Trolling success in 1960 amounted to 0.8 fish per man-hour and 5.2 striped bass per party per trip. Each party averaged 2.5 anglers who fished about 2.6 hours before being interviewed. An estimated 42,000 anglers still fished 80,100 hours on 14,700 trips and caught 127,605 fish weighing 30,000 pounds; 20,700 spot (8,270 pounds); 2,700 yellow perch (843 pounds); 1,960 striped bass (3,100 pounds) ; 1,180 eels (1,180 pounds) ; 725 white catfish (1,090 pounds); 170 croakers (149 pounds); and 170 weakfish (106 pounds).

SPORT

FISItING

SUB, V E Y O F T H E

185

P O T O M A C :ESTUARY

TABLE 7.--Total estimates of sport fishing pressure and harvest of fishes based on angler interviews (incomplete trips) by method of fishing, Areas I-IV, Potomac River, July through November, 1961~.

Fishing Pressure No. Parties No. Anglers Avg. Anglers/Party Total Man Ilours Avg. I-Iours/]Vian Rates of Catch Fish/Man-hour Fish/Party Harvest--By Species

Striped Bass Bluefish White Perch Spot Atlantic Croaker Wcakfish Yellow Perch America Eels White Catfish Summer Flounder Toadfish Totals

Trolling

Still

Total

14,000 34,500 2.46 76,800 2.23

19,900 60,600 3.04 129,700 2.14

33,900 95,200 2.81 206,500 2.17

0.50 2.77

3.72 24.23

2.52 15.40

No.

Lbs.

28,000 53,0(D I 8,450 11,800 2,270 " 686

No.

65,486

482, 42

Total Lbs.

%

54,490 15,800 22,586 148,000 704 20,800

20.7 6.0 8.6 56.2 0.3 7.9

872 14

0.3 0.1

100.1 ] 263,266

100.0

Total No.

819 1,490 28,819 ,81 2,860 4,000 ,31 11,310 73,100 21,900 7~ 370 369,000 148,000 36! O00 782 704 782 34,700 20,800 3d 7OO 872 9

3~8,,7~--

Lbs.

872 14

5.5 2.2 14.5 70.8 0.2 6.7 0.2 0.1

520,862

_

Estimates for Areas I and II were derived using combined rates of catch for these two areas. Detailed rates used for Area I I I expansion and monthly rates of Area I I I used ?o expand Area IV data. Still fishing iu 1960 produced 1.6 fish per man-hour and 8.9 fish per p a r t y per trip. I)a~%y size averaged 2.9 anglers who fished approximately 1.9 hours before being interviewed. Combined estimates for trolling and still fishing as derived from interviews indicate approximately 189,505 fish weighing 155,738 pounds wel~ caught by anglers during the 5-month period in the lower P o t o m a c River. Of this total, white perch were most numerous in the creels, totaling 52.8 percent. B y weight, striped bass accounted for 73.3 percent of the total angler catch. The angler's harvcst equaled about 23 percent of the commercial harvest for the same period. E s t i m a t e d p r es s ur e a n d harvest--1961:--Harvest data for 1961 are believed to be ~he most precise of the three years of the survey. Area I and I I estimates were combined when no differences were found between the catch rates. These figures are minimal since they are based on information for trips averaging 47.9 percent complete. Limited data in the foian of interviews and

postal response from Alva IV necessitated the use of catch-effo~ rates for Area I I I in expanding the aerial counts of Area IV. Areas I I I and IV appeared to be as closely relatcd as Areas I and I I in terms of specms composition, fishing success, methods and boat type usage. An estimated 34,500 anglem trolled 76,800 man-hours from 14,000 boats in 1961 and caught 28,000 stl~ped bass weighing 53,000 pounds (Table 7). In addition, 8,450 bluefish (weighing 11,800 pounds) and 2,270 white perch (686 pounds) were also taken. Angler success was 2.2 fish per man-hour and 2.8 fish per p a r t y per trip. Parties averaged 2.5 anglers who fished 2.2 hours prior to their in~rview. Still fishing parties totaled 19,900 parties or 60,600 anglers who caught an estimated 482,142 fish of eight species weighing 197,780 pounds. Of these, there were 819 striped bass (1,490 pounds); 2,860 bluefish (4,000 pounds); 73,100 white perch (21,900 pounds); 369,000 spot (148,000 pounds); 34,700 weakfish or gray trout (20,800 pounds); 782 croaker or hardhead (704

186

C.M.

FRISBIE

AND

I). E.

RITCHIE,

JR.

TABLE8.~Total estimates of sport fishingpressure and harvest of fishesbased on postal card response (eSinplete trips) by method of fishing,Areas I--V, I'otomac River, July 15th through November, 1960, exclusive of 300 still fishingparties in October for which no rates were available. No still fishing was observed in November. Estimates were derived using rates from Area lI1. i - -

Striped Bass Bluefish White Perch Spot Atlantic Croaker Weakfist~ Yellow Perch American Eels Whit~ Catfish Summer Flounder Toadfish

Still

Total

14,100 36,200 2.57 179,000 4.95

11,400 35,000 3.06 159,009 4.51

25,500 71,200 2.79 338,000 4.75

0.94 11.10

1.90 26.40

19.60

-i

Fishing Pressure I No. Parties No. Anglers i Avg. Anglers/Party Total Man tlours Avg. tlours/Man Rates of Catch Fish/Man-hour Fk~h/Party , t~arvest--By Species

Trolling

No.

Lbs.

168,500 352,000

I--:-

i

~;

Lbs.

3,160

5,340 172,660 [ 34.3

235,600 84,600

63,200 235,600 i 47.1 41,309 84,600 I 16,9

2,660 __559 ....

Ii Tot,l No. I !

No.

2,- 20 . . . .

1.48

2,66o

Totals pomlds); 872 eels (872 pounds); and 9 catfish (14 pounds). During the survey period, combined fishing methods produced a total of 520,862 fish weighing about 263,266 pounds. This poundage was greater than the reported commercial catch for the lower Potomac for these months. Spot dominated the total catch in 1961 (70.8 ~rccnt), followed by white perch (14.5 percent). Striped bass dropped to 5.5 percent of the total harvest, being exceeded (numerically) by weakfish. One perceives definite shifts in species composition and angler preferences when comparing Tables 6 and 7. It must be remembered that the rates of catch used in the expansion of 1960 data were derived from Area III which differs from downstremn areas in abundances of spot, we-tkfish, bluefish and croaker. COMPLETE TRIP DATA E s t i m a t e d pressure a n d h a r v e s t - 1960:--An estimated 36,200 anglers trolled 179,000 man-hours on 14,100 boats and creeled approximately 168,500 striped bass

-726

2,660 838

g330' s li;.;;4-

~f /G

76.4 41,300

13.5 8.8

0.5 O.1

726 2,660 838

0.1 0.6 0.1

o5

i: 30

0.3

L 2o I o-5 2,660] 559

f To, , bs I 63,200

99.8

weighing about 352,000 pounds (Table 8) indicated by completed postal cards. Slightly higher rams of catch were reported by trolling anglers than by still fishermen. Trollers caught 0.94 fish per man-hour, on the average, totaling 11.10 fish per pa*%y per trip. Party size averaged 2.57 anglers who fished almost 5 hours per trip. Approximately 35,000 anglel-s still fished 159,000 man-houm on 11,400 boats and caught 331,659 fish weighing about 115,394 pounds (Table 8). 0f these, there were 235,600 white perch weighing 63,200 pounds; 84,600 spot (41,300 pounds); 3,160 striped bass (5,34(I pounds); 2,600 toadfish (1,300 pounds); 2,420 yellow perch (726 pounds); and 559 catfish (838 pounds). Still fishing parties averaged 3.1 anglers who fished 4.5 houm per trip. They creeled about 1.9 fish per man-hour or 26.4 fish per party per trip. When both methods were combined, an estilnated 71,200 anglers on 25,500 })oats tished a tot,d of 338,000 man-hours. They harvested 501,200 fish of seven species, weighing about 467,400 pounds. Angler harvest mnounted to 69 percent of the

SPORT FISHING SURVEY OF TIIE POTOMAC ESTUARY

]87

TABL]~ 9.--Total estimates of sport fishing pressure and harvest of fishes based on postal card response (complete trips) by method of fishing, Areas I - I V , Potomac River, July through November, 1961. I Trollingt Still i Total2 Fishing Pressure No. Parties No. Anglers Avg. Anglers/Party Total Man Hours Avg. tIours/Man Rates of Catch Fish/Man-hour Fish/Party

Harvest--By Species Striped Bass Bluefish White Perch Spot Atlantic Croaker Weakfish Yellow Perch American Eels White Catfish Summer Flounder Toadfish Totals

13,300 34,600 2.61 159,900 4.62

19,900 66,800 3.35 292,900 4.38

0.64 7.78

3.74 54.99

No.

Lbs.

89,800 10,400 2,060

168,300 14,600 618

- 915

549

No.

=:

[

i03-,

5

2.64 36.1

Lbs.

.

.

33,200 101,400 3.05 452,80O 4.46

i

Total No.

3,130 12,6ooI 206,460'. 61,300 803,300 321,300 5,910 [ 6,570 42,700 I 72,115 174 15~32 152 75i 112 3~ 5 76. 38 I _ _ ? 6 .

-

....

.

.

.

%

Total Lbs.

80

191,300 17,730 61,918 321,300 5,910 43,249 174 152 1 112i 5 38

1 .o

17.2 67.1 0.5 6.0 <0.1 <0.1 <0.1 <0.1 <0.1

% 29.8 2.8 9.6 50.0 0.9 6.7 <0.1 <0.1 <0.1 <0.1 <0.1

.

.... 184,067 1 ~ " : , ~ I 457,821 1,197,434 - - 9 9 - ~ - - 641,8881 b. . . . 99.8

No rates of catch were available for 1,018 boats trolling. -~Estimates for Areas I and I I were derived using combined rates for these two areas. Detailed rates were used for Area I I I expansion and monthly rates of Area I I I were used 1,o expand Area IV data.

fish, catfish, and summer flounder totaled 889 fish, weigtfing 481 pounds. Still fishermen averaged 3.7 fish per man-hour and 55.0 fish per trip. Parties averaged 3.4 anglers who fished 4.4 hours per completed trip. Total sport harvest by both methods in E s t i m a t e d pressure a n d h a r v e s t - 1961:- -An estimated 34,600 anglers trolled 1961 amounted to 1,197,434 fish of 11 159,900 man-houm from 13,300 boats and species, weighing 641,888 pounds. Spot were landed approximately 103,175 fish weighing most important, comprising 803,300 fish 184,067 pounds (Table 9). These included (67.1 percent) weighing 321,000 pounds. 89,000 striped bass (168,300 pounds) ; 10,400 White perch were second with 206,460 bluefish (14,600 pounds); 2,060 white perch (17.2 percent) weighing 61,918 pounds. (618 pounds); and 915 weakfish (549 Striped bass were third with 95,500 (8.0 pounds). Successful trollers in 1961 creeled percent) t)ut ranked ~cond in poundage 0.6 fish per man-hour and/or 7.8 fish per importance with 191,300 or 2(,).8 percent of pal~y. An average of 2.6 anglers per party the total. Weakfish, bluefish, croaker, yellow perch, eels, toadfish, catfish and summer fished 4.6 hours per completed trip. An estimated 66,800 still fishermen on flounder followed in importance in angler 19,900 boats took approximately 1,094,25(') catches in 1961. fish weighing 457,821 pounds. Their catch CONFIDENCE LIMITS included 803,300 spot (321,300 pounds); Confidence intervals of Areas I, II, and 204,400 white perch (61,300 pounds); 71,200 weakfish (42,700 pounds); 6,570 croakers III, the major portion of the area covered, (5,910 pounds); and 5,700 striped bass ranged from 5.4 to 9.3 percent (Table 10). (23,000 pounds). Yellow perch, eels, toad- In both interview and postal card estimates

commercial harvest of 677,406 pounds during the~ same periods for the lower Potomac River in 1960. This may seem out of proportion but these months arc usually lean ones for the commercial tishelTaen.

188

C.M.

F R I S B I E AND D. E. R I T C H I E , JR.

TABLE 10.--Summary of results for the Potomac Estuary, 1961, showing calculated confidence limits. Data are sums of estimates made for major and minor study areas. Estimates were derived from airplane counts of boats fishing and fishing pressure curves. ~Test for confidence limits (95 percent) front Snedecor (1956:47-48). Type of Data

. Irtter,/iew Data Trolling P,oat Count Fishermen F/shermen- Ilrs. Ilarvest (No. of fish) Still Fishing Boat Count Fishermen Fishermen-Hrs. Harvest (No. of fish) Postal Card Data Trolling Boat Count Fishermen Fishermen-Hrs. Ilarvest (No. of fish) Still lr Boat Count Fishermen Fishermen-His. tIarvest (No. of fmh)

i~Perc;nt- IConfidence Limits

I Total .

.

.

,2.2001 30,300 ; 67,600 33,300

I Upper I r..... r

.

6.0% 5.7~ 6.4%

i i

i

12,9001 32,1001 71,300 35,400!

11,600 28,500 63,700 31,200

18,8oo [ 6.8% 56,900 I 7.7% 124,000 I 7.2% 476,800 9.3%

20,1001 17,500 61,3001 62,500 ,33,000 116,000 521,0001 432,000

11,400 30,100 139.000 84,300

5.7% 6.7% 7.4%

,2,100 10,800 32.1001 28,000 149,0001 128,000 90,6001 78,000

19,0OO 62,400 278,000 1,076,000

6.6% 7.8~ 7.5% 8.2%

20,300] 17,800 67,300! 57,500

7.5%

I :

Estimates were derived from ArenasI, II, and III, the most cornpletely sampled areas, and should not be compared with other summations presented earlier.

ll.--Residence of Anglers Fishing in the Lower Potomac Estuary.

TABLE

Location

Washington, D. C., Prince George's and Montgomery Counties, Md., Arlington and Fairfax Counties, Va. Local M a r y l a n d - Charles County Greater Baltimore Area Other Maryland Counties Local Virginia--King George and Westmoreland Counties Other Virginia Counties Other Sta~es

1960 1961 PercentagelPercentag e

28.4

30.6

25.7

12.2

1.8 3.0 23.5

2.0 7.2 22.1

17.0 0.6

25.4 0.4

the confidence limits derived from trolling data are more narrow than for still fishing data. Confidence limits for a similar survey in the nearby Patuxent Estuary in 1960 (Shearer, et al., 1962:9) were markedly broader. A possible explanation of these differences m a y be the vastly different sizes of the two surveys and the aerial

counts which were the basis of the expanded figures in the Potomac survey. I:~ESIDENCE OF fkNGI,EHS

Residents of the Washington, D.C. area, including several primarily urban Maryland and Virginia counties, as delivcd by interview in ] 960 and by postal card response in 1961, were the most important u ~ r s of the area (Table ] 1). Residents of Charles County were second in abundance in 1960 but declined by half in 1961. Conversely, a marked increase in l~sidents of other Virginia counties was noted in 1961, especially from the ILichmond area. Other Maryland residents fished the Potomac more in 1961 (4.2 percent). These fluctuations may have resultcd from fishing success, quickly publicited by the "local angler grapevine." It is also probable that mole distant anglel~ were drawn to the Potomac in ]961 by virtue of having heard of good catches in the preceding season. Unfortunately, no data is available to test this hypothesis. E C O N O M I C A S P E C T S OF T H E S P O R T F I S I I E R Y

Data from 1961 economic postal card questionnaires indicated the following average expenditures per party per trip: b a i t - $1.64 (live bait and artificial lures) ; boat-gas and oil---$3.57; rent--S4.23; food--S3.38; refreshments--S1.94; other--S0.57. These expenditures average $15.33 per party per trip or S~.78 per man per trip, or approximately $480,000 during the 5-month survey period, excluding travel. Of this amount, nearly 81 percent was spent near the river and 19 percent near their homes. The average reported value of fishing equipment including boats, motors, tackle and other gear amounted to S2360 per party. The average Potomac River angler fished 29 times per year and traveled 91 miles each trip. Assuming 4r per mile (National SUlwey of fishing and hunting, 1960:64), travel expenses totaled 8113,592 and expenses and mileage costs together equaled $593,592 in 1961 or $5.81 per pelson per trip. The value of equipment used is not included in this total since ihe actual number of boats u~'d sevel'M times yearly was beyond the scope of this survey.

SPORT FISHING

SURVEY

Total expenses of $5.81 per angler in the lower Potomac are less than those from a statewide survey by Buzzcll (1954:1-14), which averaged $9.61. However, included in his average cost (and not in the present survey) were fishing tackle, special clothing and equipment, and lodging, amounting to $1.96. Subtracting this amount from 89.61 we get $7.65 which is 24 percent greater than 1961 expenses. Thus, it appears that trip expenses in Maryland tidal wa~rs have declined in the last ten years. This discrepancy may be explained by noting that Buzzell's survey covered a greater proportion of "livery rentul" fishennen who are suspected to spend morn than those owning their own boats. The average yearly expenditure of Potomac anglers in 1961 anmunted to $167.32 as compared to Buzzell's statewide estimate of $96.06 in 1954. This greater expen~ by Potomac anglers was probably reflected in the trip frequency, 29 trips per angler in 1961 versus a 1953 statewide "average" of 10 trips per year. Accuracy of fishermen reporting their expenses may have affected results; however, it is believed that pemonal contact with the fishermen produced more accurate l~ports than a questionnaire depending on the angler's memory of a year's expenses. Even so, this method could be too costly in a large scale survey and might better be replaced by a mailed questionnaire as used by BuzT~ll (1954), Walker (1954), Mahoney (1960), Pelgcn (1955), and Wallace (1952). The possibility of bias existed with anglers not returning the postal card questionnaire until a follow-up letter was sent them. Wallace (1952) and Pelgen (1955) noted that anglers replying to a follow-up letter in mail questionnaire SUl~eys spent less per trip. Contrary to these studies, tardy Potolnac River respondents spent slightly more than initial respondents. Thus, the expansion of the economic data does not appear to have been biased. BIOLOGICAL

ASPECTS

OF STRIPED

BASS

Scale samples, weights, and measurements were taken from 341 striped bass in 1959, 535 in 1960, and 153 in 1961 (Table 12). In 1959, age group II striped bass comprised

OF THE

189

POTOMAC ESTUARY

TABLE 12.--Age composition by percent and fork lengths and weights of angled striped bass taken during the 1959-1961 sport fish survey in the Potomac Estuary. Fork Length (inches)

I

Rango

I

Range

Average

10.96 i . 2.3 . . . 9.5-11.3 . . 85.3 10.8-17.5 14.171 9.1 15.3-18.5 16.85 2.3 18..5-21.9 20.04 0.6 21.2-21.9 2 55 i

0.5-0.7 0.5-2.5 1.6-2.8 2.6-5.1 4.6-4.4

0.54 1.30 2.11 3.51

Per- I Age NilE- cent= I Group bet age of Total 1959

I~ III VI VII

Weight (poun~ ~munds)

419

1

0-~

L379

81.7 9.2 2.8 2.2 2.2 0.2

0.2-10.7 9.3-18.0 15.0-18.8! 15 7-21.71 19.6-21.01 23.7-26.91 29.0

8.34 0.12-0.56 0.28 13.02 0.50-2.69 1.18 16.26 1.50-3.56 2.36 19.96 2.93-5.37 3.91 22.001 3.50-7.12 5.40 25.00 I 4.62-8.00 7.04 29.00 10.50 10.50

37 73

24.2 47.7 12.4 4.6 5.9 3.3 1.3 0.6

10.8-12.9, 10.8-16.5! 14.6-20.11 19.0-24.71 20.4-26.41 25.7-28.8[ 27.5-27.71 28.1

11.531 0.56-1.00 0.77 12,92 0.50-2.75 1.02 17.00 I 1.50-3.50 2.32 22.30 I 3.25-6.62 2.40 23,181 3.37-7.75 5.56 26.50[ 6.56-9.50 7.44 26.60 I 9.6240.0t 9.81 28.10 10.00 10.90

320

32.0

1V9

11~

Total

III VI VII

49 15 12 12 1

1.7~

Total

1961

II III VI VII VIII

lO

Total Includes eight sub-legal sized fish taken b y authors for biological studies.

85.3 percent of the sample; in ]960, 81.7 percent; and in 1961, 47.7 percent. Shearer, et al. (1962:14) reported 86.0 percent age group II fish caught from the nearby Patuxent Estuary in 1960. The average length of the 1957 year-class, caught in 1959, was considerably greater than that of the dominant 1958 year-class which entered the fishery in 1960. These fish exhibited a wide length-range in 1960, indicating possible stunting in part of the hatch. The average length of 1959 year-class fish was slightly less than the 1958 year-class when they were, two-year-olds. Mansueti (1961: 1-36) reported two-year-old males averaged 11.7 and females ]1.5 inches fork length. Merriman (1941:49) noted that comparisons of growth rates of different year-classes am possibly fallacious and should be used with caution. Age group I striped bass (in second year of growth) compri~d 24.2 percent of the sample fish of the 1961 spol% fishery ranging in length from ]0.8 to 12.9 inches fork

190

c.M.

F R I S B I E AND D. E. R I T C H I E , J R .

length and averaging 11.5 inches (Table 12). Maryland striped bass d o n o t reach the legal limit of 12 inches total length until sometime within their second year, yet here we found fast-growing age group I fish contributing heavily to the sport catch. Those under about 11.2 inches fork length were sub-legals but still comprised a part of the angler harvest. Human error in scale reading was mini: mized by employing two experienced readers who checked each other on questionable scales. When the readers could not agree on difficult readings they rejected these scales (about 2 percent) from the sample. The ranges of weights are within reasonable limits of striped bass taken by sizeselective commercial gear (Mansueti, 1962: 22). The range and the average weights of angler-captured striped bass illustrate the variation in sizes of fish by age class which are taken during summer and full months (Table 12). MOst age and growth studies deal with calculated length and/or weight at the beginning of the growth season, or near their "birthday." Conclusions

In 1959, of 346 fishing parties interviewed in the survey Area III, 116 or 33.5 percent returned postal card questionnaires. In 1960, some 827 parties were interviewed, resulting in 329 postal cam returns (40 percent). Interviews in all areas in 1961 totaled 828 parties, of which 549 or 66.3 percent returned completed postal questionnaires. The increase in postal response in 1960 and 1961 may be attributed to the opportunity presented the angler to answer the question "Are you satisfied with fishing in tidewater?" and the follow-up letters to non-respondents. No important differences were found between data from initial and follow-up responses. Rates of catch for 1959 were 0.27 fish per man-hour for incomplete trip data and 0.48 fish per man-hour for complete trip data indicating some possible bias in the reporting of catches. Small boats declined in numbers while party boats remained reasonably stable. Trolling was the dominant fishing method for striped bass with August

fishing pressure being the greatest during the survey period. Still fishing pressure also was heaviest in August, but declined earlier than trolling. The dominant 1958 year-class of striped bass probably resulted in the high rates of catch in 1960 when they first entered the fishery. August 1960 and November 1961 were the most productive months for trolling anglers. August 1960 and October 1961 were most productive for still fishing anglers. Party boats had higher rates of catch than smaller boats. Poundage of striped bass caught was greatest in 1960 while white perch, although producing the greatest numbeps, were second in importance by weight. Spot ranked third in 1960. The spot catch of 1961 was greater than all other fish by number and by weight. Striped bass caught in 1961 ranked second by weight, followed by white perch. The narrow range confidence limits of 1961 fishing pressure and harvest indicated a fair degree of precision for the estimates. Virtually no differences were found in rates of catch between incomplete and complete trip data. Significant differences found for party boats were probably associated with a sampling error. These findings strongly suggest that either interview or postal card surveys alone could be used in future surveys to produce catch rates which, when expanded by aerial boat counts, would result in total harvest estimates. Residents of the Washington, D.C., metropolitan area were most important to the sport fishery. Strong fluctuations oeeurred yearly in numbers of local fishermen. About 81 percent of the Potornae River angler's expenses (including travel costs) was spent near the river. An estimated $594,000 was spent during the 5-month 1961 survey. The average angler expenditure was 85.81 per trip for 29 trips per year. Personal interviews and subsequent postal response appear to be as valid as mail questionnaires for estimating trip expenditures. Age group II striped bass contributed the bulk of the angler's catch in the lower Potomac, making up 48 to 85 percent of the catch, as determined from scale samples

191

SPORT FISHING SURVEY OF TIIE POTOMAC ESTUARY

during the three years of the survey. '['he i957 year-class, of near average size, contl~ibuted a higher percentage to the "mgler's catch in 1959 than the 1958 year-class did in 1960. The broad range in lengths of the 1958 dominant year-class of striped bass taken by anglem in 1960 reflect the variation possible in the growth of large year-classes. Some evidence of stunted growth was apparent for the 1958 year-class. Indications were that part of the 1960 year-class was composed of fast-growing individuals that compri~d 24 percent of the angler's catch in 1961. LITERATURE CITED BI~ZZELL, R. 1). 1954. An economic study of the Maryland sport fishery. In R. D. Buzzell and E. T. Walker; A study of sport fishing in tidewater Maryland. Md. Dept. Research & Educ., Resource Study Rept. (4), Pt. 1:5-14, Ft. 11:5-6. CALHOUN, A . J . 1950. California angling catch rccords from postal card surveys: 1936-1948; with an evaluation of postal card non-response. Calif. Fish and Game 86(8):177-284. DI COSTA.~ZO,C. 1956. (;lear Lake creel census and evaluation of sampling techniques: pp. 1729. In Symposium on sampling problems m creel census, 1956. Iowa Coop. Fish. Res. Unit, lowa St. Coll. Press, Ames, Iowa. ELS~'R, HAROLD J. 1960. Creel census results on the Northeast River, Maryland, 1958. Chesapeake Sci. I(1):41-47. HILDE~RA.~D, S. F. ANn W. C. SCHROEDER. 1928. Fishes of the Chesapeake Bay. U.S. Bur. Fish. Bull. 43(I):I-366. JESSEN, R . J . 1956. Comments and suggestions on designing creel censuses, pp. 50-6. In Symposlum on sampling problems in creel census, 1956. Iowa Coop. Fish Res. Unit, Iowa State Coll. Press, Ames, Iowa. M,~AI()NEY, J. 1960. An economic evaluation of California's sport tisheries. Calif. Fish and Game. 46(2):199-209. MANSUETI, R . Z . 1961. Age, growth and movements of the striped [)ass, Roecus saxatilis, taken in size selective tishing gear in Maryland. Chesapeake Sci. 2 (I -2) :9--86. MERaIMAN, l). 1941. Studies on the striped bass (Roceus saxatilis) of the Atlantic Coast. U.S. Fish & Wildl. Serv. Fish Bull. 50(35):1--77.

FELGEN, O . E . 1955. Economic values of striped bass, salmon, and steelhead sport fishing in California. Calif. Fish and Game. 4I (1):5-17. PLOSILA, D.S. 1961. Lower Susquehanna River sport fishery survey, 1958-1960. pp. 55-78. In The Susquehanna Fishery Study, 1957-1960. Md. Dept. Research & Educ. Contrib. (169):1-81, ill. RICnARDS, C . E . 1962. A survey of salt-water Ort fishing in Virginia, 1955-5960. Chesapeake i. 8(4):223-85. ROUNSEFELL, G. A. AND W. H. EVERHART. 1953. Fishery Science; its mcthods and applications. John Wiley & Sons. New York. xii + 444. RYAN, J. II. 1959. California inland angling estimates for 1954, 1956, and 1957. Calif. Fish and Game. 45 (2) :93-109. SIIEARER, L. W., D. E. RITCHIE, JR. AND C. M. FRISBIE. 1962. Sport fishing survey in 1960 of the lower 1)atuxent estuary and the 1958 yearclass of striped bass. Chesapeake Sci. 8(I):i-17. SKINNER, J. E. 1955. California state-wide angling estimates for 1953. Calif. Fish and Game. 41 (I):19-32. SNEDECOR, G. W. 1956. Statistical methods. Iowa St. Coll. Press, Ames, Iowa. xiii -6 534. TRUITT, R . V . 1938. Sport fisifing in Maryland. Md. Dept. Research & Educ. Pub. 26:1-16. , AND V. D. VLADYKOV. 1937. The importance of sport fishing in Maryland. Trans. Am. Fisheries Soc. 66(2):405--5. UNITED STATES COAST _~N.I) GEODETIC SURVEY. 1960. Tide tables, east coast, North and South America, U.S. Dept. Commerce, 275 pp. UNITED STATES FIsH AND WILDLIFE SERVICE. 1961. National survey of fishing and }mAting, 1960. U.S. Fish & Wildl. Serv. Cir. (120):iv + 73. WALKER, E . T . 1954. An intensive survey of the Patuxent River sport fishery. In R. I). Buzzell and E. T. Walker: A study of sport fisifing in tidewater Maryland. Md. Dept. Research and Edue., Resource Study Rept. 4, Pt. I, 14 pp., Pt. II, 6 pp. WALLACE, 1~. F. 1952. Economic aspects of wildlife resources of the State of Washington. State Coll. of Wash., Econ. & Bus. Studies, Bull.

~c

(19):1-4e.

WELLS, 1~. C., R. HENDERSON. 1929. Chesapeake Bay. pp. butions to general

.,,,

K. BAILEY, AND: E. ~). Salinity of the water of 105-151. In Shorter contrigeology. U.S. Geol. S~rv.

Prof. Pap. 154-C.

Chesapeake Biological Laboratory Solomons, Maryland