Marine Biology (1994) 121:211-217

9 Springer-Verlag 1994

B. Morales-Nin

Growth of demersal fish species of the Mexican Pacific Ocean

Received: 10 December 1993 / Accepted: 4 August 1994

A b s t r a c t The growth of 24 species of demersal fish caught off the Sinaloa-Nayarit coast and in the Gulf of Tehuantepec (Mexican Pacific Ocean) was determined by means of length-frequency analysis. Fishes constitute an important bycatch of the penaeid shrimp fishery, and 235 species were identified in catches made on research cruises in both areas in 1989 to 1992. Growth rates (cm yr -1) ranged from 0.13 cm for lutjanids and serranids to 0.95 cm for the carangid Selene peruviana; the other species displayed growth rates within this range. Growth varied seasonally, with minimum growth in spring, and is probably related to seasonal changes in the waters of the area. By means of length-frequency analysis, we determined von Bertalanffy growth parameters for the primary species of this multispecies fishery. Such data is fundamental for the future commercial exploitation of these fishes.

Introduction Estimation of growth in tropical marine fish has long been problematic because of the supposed lack of annual rings in their hard structures (scales, otoliths and vertebrae). Moreover, their "continuous" spawning has been assumed to render impossible growth analysis based on length-frequency data (Mohr 1921). However, during the 1960s and 1970s, it was realized that tropical marine fish generate annual rings in their hard parts under a wide range of conditions. Also, it was found that growth could be estimated for many tropical fish stocks by analyzing seasonal growth rings within the otoliths (Poinsard and Troadec 1966; Longhurst and Pauly 1987; Morales-Nin 1989, 1992).

Communicated by J. M. Pdr~s, Marseille B. Morales-Nin CSIC-Institut d'Estudis Avangats de les Illes Balears, Crta. Valldemossa Km 7.5, E-07071 Palma de Mallorca, Spain

While spawning in tropical fish is often more prolonged than in their temperate fellows, it is usually concentrated in one or two periods each year. Changes in fish spawning are only partially responsible for recruitment fluctuations. The occurrence of recruitment windows during larval and juvenile stages (Bakun et al. 1982) can vary seasonally, even when egg production is constant. These recruitment fluctuations then generate the abundance modes which permit analysis of length-frequency data (Pauly 1984). The demersal fish fauna of the Mexican Pacific Ocean has been but poorly studied; most work has been carried out in the Gulf of California, and has been based on aspects of systematics (Walker 1960; Castro-Aguirre et al. 1970; van der Heiden et al. 1982; van der Heiden 1985; Thomson et al. 1987; van der Heiden and Findley 1988); commercial fishery (Chfvez and Ramos-Padilla 1974; Mathews et al. 1974; Arvizu-Martfnez 1987; Stromme and Saetersdal 1988; Acal and Arias 1990) and community structure (Bianchi 1991; Plascencia-Gonzflez 1993). Biological data for demersal species are scarce; a preliminary study was made on the growth of Synodus evermanni based on otolith growth patterns (Morales-Nin 1993), and a biological study on Caulolatilus affinis and C. princeps has also been carried out (Elorduy 1993). The present paper describes the growth of 24 demersal species caught off the northwestern and southern coasts of the Mexican Pacific Ocean, determined by length-frequency analysis. Growth rates in both areas and between species are discussed.

Materials and methods Data collection As part of an EU-sponsored research project ("Requirements for the restructuring of Mexican Pacific demersal fisheries"), eight research cruises (CEEMEX-P1 to CEEMEX-P8) were carried out by the R.V. "El Puma"; five in the Sinaloa-Nayarit area and three in the Gulf of Tehuantepec (Fig. 1) from 1989 to 1992. During each cruise, the demersal macrofauna was sampled with a C-80 shrimp trawl net. The fishes from each catch were identified and measured, and their total lengths were rounded down to the nearest 1 cm. The length-fre-

212 Fig. 1 Study areas in Mexican Pacific Ocean. A Sinaloa-Nayarit area; B Gulf of Tehuantepec ( 9 stations sampled in CEEMEX research cruises)

A ['~ W

~

168 ~

16z ~

O

166 ~

16s o N

25~

Q

2 4 ~_

.. M A Z A T L A N

.:'"

\

23'

220" 8

I9M A R I A S ~'~. Q

I

I

B N

9~6~

I

o

9 5 ..

912 o

9~4~

s oo

GTEHUANTEPEC

oO

I

I

quency distribution for each species was determined for each cruise. Growth parameters were calculated for each species on each cruise by means of a length-frequency analysis that covered a large size range and included enough fishes to produce clear modes. The number of fishes measured and their length ranges for each cruise are shown in Table 1. The length-frequency for each species and area was analyzed by the ELEFAN method (Gayanilo et a1.1988).

~

r

I

E

Length-frequency analysis Variations in the frequency of age-classes over time can be determined by direct observations (Petersen 1891), or by using a computerized method developed from the Hasselblad (1966) technique for separation of modal length-classes into a length frequency matrix (MacDonald and Pitcher 1979; Schnute and Fournier 1980). Pauly and David (1981) analysed such time sequences by assuming that

213 Table 1 Length ranges (cm) and numbers of species sampled on each CEEMEX cruise. Cruises CEEMEX P4, P5 and P7 were in Gulf of Tehuantepec, remainder were off Sinaloa-Nayarit coast Species

P1

Albula vulpes

1-19 31

Bagre panamensis

P2

P3

P5

6-37 22

6-40 164

6-12 332

6-12 160

P6

P7

P8

10-36 61

Balistes polylepis Porychthys analis

P4

5-39 47

8-19 252

Engoyophrys sanctilaurenti

4-15 483

Monolene asaedai Brotuloides cf. enmales

5-13 178 5-22 580

Selene peruviana

5-21 783 12-21 81

Diapte rus peruvianus Diapterus aureolus

8-14

6-13

Pseudopenaeus grandisquamis

76 7-17 48

254 7-24 936

7-21 53

7-19 70 7-29 79

Lutjanus peru Ciclopsetta querna Citharichthys platophrys

6-29 57 4-15 2126

4-35 704

8-12 87

Syacium latifrons Syacium ovale

9-18 79

9-20 50 12-29 81 18-43 65

Pomadasys axillaris

5-17 311 6-17 74 16-70 16

Pomadasys nitidus Epinephelus analogus Diplectrum macropoma

6-24 603

9-24 67 10-29 842

Synodus scituliceps Prionotus stephanophrys

6-25 579 6-26 355

6-18 208

7-18

Diplectrum labarum Synodus evermanni

5-55 215 14-20 178 5-12 765

5-23 358 9-16 50

7-19 215

7-24 635

4-24 464

8-28 373

the mode of each age-class is best described by a von Bertalanffy growth curve. A seasonal growth curve (Pauly 1979) was used for growth determination: Lr=L=(1-eK(t-t~ + CK/au sin(2u[t-td)), (1) where t=time, ts=the commencement of variations in sinusoidal growth with respect to t=0 [ts=WP+0.5, where WP=that point in winter at which minimum growth occurs (0
8-19 31

10-20 102 7-20 63 20-36 39

8-32 334 5-12 456

6-27 356

7-18 477 7-18 66

459 7-19 67 8-23 499 11-38 79 6-12 113

6-12 123

To estimate L~, Wetherall et al. (1987) used a regression method derived from the formula of Beverton and Holt (1957), whereby Z=the total instantaneous mortality coefficient, L~ and K are von B ertalanffy growth parameters, and Lm=mean length in a random sample of fish above length L c, Lc=the length selected; it is assumed that fish larger than this have been fully recruited to the fishery. The mean length offish greater than L C(i. e., Lm) is a linear relationship between L~ and Z/K:

Lm=L~[{ (Z/K)/(Z/IO+ 1) }(L~-Lc) ].

(2)

After estimating L~ for each species by this method, a yon Bertalanffy growth curve was fitted to the length frequencies using the ELEFAN I procedure (Pauly and David 1981). By restructuring the frequencies, this procedure aids the identification of cohort peaks independent of their height or assumed shape, The frequency Fr of each

214 length-class i (i=1... n) is divided by the moving average (MAi) over five length-classes. The values of FAi=(Fi/MAi) identify peaks (FAI>_ 1) and troughs (FAi,< 1). The average adjusted frequency value, FA, is then computed and the final transformation is made according to the equation: F~'=FAJFA-1. (3) In a set of restructured length-frequency samples (ns=number of samples), a number of peaks (np) lie within each ns sample. Each peak (F/') is presumed to represent a distinct age-class, and any growth curve passing through a peak would intersect only one of the lengthclasses constituting that peak. Thus, the maximum sum of positivepoint values that can be accumulated by a growth curve equals the sum of all np peaks in all ns samples; this is the available sum of peaks (ASP). Any growth curve fitted to a restructured length-frequency matrix will intersect a number of points within the matrix. Summing the restructured frequency values corresponding to these points gives the explained sum of peaks (ESP). The fit of a growth curve passing through a restructured lengthfrequency data matrix is determined by the number of intersected peaks in relation to the total number of available peaks. The value obtained for the goodness-of-fit index, Rn=ESP/ASP (0
R es u l t s and discussion

This study was not centred on commercially exploited fish species, since only a few littoral species are exploited and these were rare in the research-cruise hauls. It was thus considered appropriate to gather data for as many species as possible. All species with sufficiently representative length-frequency data have been analyzed, even if encountered only during one cruise. The growth parameters L~ and K were calculated for 24 species (Table 2).

Fig. 2 Growth of all fish species studied, expressed as loga rithmic relationship between asymptotic length (L~cm) and von Bertalanffy growth c o e f f i cient (K yr- 1). Species codes are explained in Table 2

Asymptotic length L~ and the growth coefficient K were correlated in order to study trends between species. Pauly (1979) and Munro and Pauly (1983) used the growth-performance index, ~= 21og(L~) +log(K), as a taxon-specific index of growth performance. Manooch (1987) later employed the growth-performance index to graphically summarize the growth data of tropical lutjanids and serranids. Using the same criteria, log (K) was plotted against log(L~) for all the species studied. The resulting plot (Fig. 2) was linear with a negative slope, its y-intercept provides an index of growth performance. The regression line (Fig. 2) is log(K)=0.6319-0.69025 log(L~). Standard error estimates for the slope and intercept are 0.1512 and 0.156, respectively, and the correlation between the two parameters is relatively low (r2=0.4545). A clear inverse relationship existed between theoretical m a x i m u m size (L~) and the von Bertalanffy growth coefficient (K). The plot shows a tendency towards a linear arrangement of the data points representing the various species, with slow-growing fishes at the bottom right and the fast-growing at the top left. The Lutj anidae and S erranidae, long-lived species which attain large sizes, are clearly differentiated in the plot. Selene peruviana is the fastest-growing species, while the majority of the species display intermediate values. In those cases where data were sufficient to calculate seasonal growth (Eq. 1), most species exhibited similar W P values, indicating minimum growth in spring. C values were moderate, reflecting seasonality in this tropical ecosystem (Table 2). For species common to both study areas, growth rates were greater in the south (Gulf of Tehuantepec) than in the north (Sinaloa-Nayarit). The one exception was Albula vulpes, which displayed the same growth rates in both areas (Table 2). The Mexican Pacific Ocean is characterized by complex current patterns. The surface currents off the Mexican and Central American coasts are dominated by two main systems: the California Current and the North Equa-

9 sp

,SL -0.2

-" M A ' ~ D ~ DL i~DP PAX" ~

-0.4

9PN

"SO

,SS

"PG ,PS

,BPO

.DL

"~---~AX

PA"

.CO.~

|

v

O) O .._1

,MA

-0.6

-0.8

,LP EA.

-1 1.1

J

I

I

I

P

P

I

I

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

Log (L00)

215 Table 2 Asymptotic length (L=), Von Bertalanffy growth coefficient (K), seasonal growth oscillation (C) and minimum point of growth (WP) for species studied, species codes are used in Fig. 2 (Sin-Nay Sinaloa-Nayarit area; GT Gulf of Tehuantepec) Species

Species Code L=(cm)

Kyr 1

Albulidae Albula vulpes

AV

47.3

0.275

Sin-Nay

Ariidae Bagre panamensis

BP

44.1

0.37

Sin-Nay

BPO

37

0.49

PA

25.2

0.38

Sin-Nay

ES MA MA

21 17 13.4

0.56 0.31 0.64

Sin-Nay Sin-Nay GT

BE

24.2

0.45

Sin-Nay

SP

21

0.95

DP DA

21 13.6

0.65 0.57

PG PG

25 20.3

0.5 0.61

LP

61.4

0.14

GT

CQ CP SL SO

29.3 32 19.1 24.1

0.35 0.24 0.86 0.72

Sin-Nay Sin-Nay GT Sin-Nay

PAX PAX PN

29.2 21.1 17.9

0.42 0.51 0.36

Sin-Nay GT GT

EA DM DL DL

97.3 17.8 24.2 18.5

0.12 0.61 0.41 0.6

Sygnodontidae Synodus evermanni Synodus scituliceps

SE SS

24.5 39

Triglidae Prionotus stephanophrys

PS

28

Balistidae Balistes polylepis Batrachoididae Porychthys analis Bothidae Engyophrys sanctilaurenti Monolene assaedai Brotulidae Brotuloides cf enmelas Carangidae Selene peruviana Gerridae Diapterus peruvianus Diapterus aureolus Mullidae Pseudopenaeus grandisquamis Lutjanidae Lutjanus peru Paralichthydae Ciclopsetta querna Citharichthys platophrys Syacium latifrons Syaeium ovale Pomadasyidae Pomadasys axilIaris Pomadasys nitidus Serranidae Epinephelus analogus Diplectrum macropoma Diplectrum labarum

torial Current. The California Current, which originates in the Arctic, carries water southward along the coasts of California and Baja California. This water mass is easily identified by its low salinity, low temperature and high dissolved oxygen content. The California Current meets the North Equatorial Current (which flows from east to west at maximum velocities slightly in excess of 1 km/h) near Cabo San Lucas and Cabo Corrientes (at the mouth of the Gulf of California). In this area, salinity and temperature gradients are very high. Although the principal oceanic circulation is driven by these two currents, there are local and seasonal current patterns that affect the northwest coast of Baja California and

C

0.55

0.7

WP

0.2

0.3

Area

GT

Sin-Nay Sin-Nay Sin-Nay

0.2 0.2

0.5 0.5

Sin-Nay GT

GT Sin-Nay Sin-Nay GT

0.2 0.2

0.5 0.3

0.59 0.75

0.5

0.2

Sin-Nay GT

0.47

0.55

0.4

Sin-Nay

the gulfs of California and Tehuantepec. In these areas, water flows southeast during winter and northwest during summer. Between February and April there is a strong southwest current of 0.54 kin/h, and between June and August a northwest flow of 0.72 km/h. The southeast Central American coast is strongly affected by winds from both the Pacific and the Atlantic oceans. Winds blowing from the Atlantic are notable during the dry season (NovemberApril) and in summer. The winds and the resulting upwelling waters decrease water temperatures by 2 to 6 C ~ lower than in any other Central American region (Blackburn 1962, 1966; Wyrtki 1966, 1967; Fiedler 1992). This upwelling, which increases productivity, food availability

216 arid o x y g e n content, could e x p l a i n the more rapid growth observed in fishes in the south of the study area. Similarly, seasonal changes in oceanographic conditions, by directly affecting metabolic d e m a n d s ( m a i n l y through variations in temperature and o x y g e n content) and indirectly p r o v i d i n g more food, could be linked to seasonal variations in growth. Data on age and growth rates are f u n d a m e n t a l requirements for both studies on fish b i o l o g y and for the setting up of m a n a g e m e n t policies for p r e v e n t i n g overexploitation of fishery resources. L e n g t h - f r e q u e n c y analysis of tropical fishes has some s h o r t c o m i n g s arising from protracted r e c r u i t m e n t periods and m a j o r overlaps of adjacent ageclasses ( M a n o o c h 1987). Nevertheless, such analysis permits the e s t i m a t i o n of growth parameters when other approaches are not possible. D e m e r s a l fishes in the M e x i c a n Pacific O c e a n are h e a v i l y exploited as a by-catch of the shrimp fishery (Acal and Arias 1990), and could b e c o m e the basis for a direct fishery. I n f o r m a t i o n on their b i o l o g y is therefore needed to provide the basis for future m a n a g e m e n t of stocks. The diversity of demersal fish species is impressive, 235 species were identified during the C E E M E X cruises (van der H e i d e n personal c o m m u n i c a tion). H o w e v e r length-based methods are rapid and can provide basic data such as those presented in this paper. In future studies, age data from otolith interpretation could be used to c o m p l e m e n t l e n g t h - f r e q u e n c y analysis and thus i m p r o v e the accuracy of growth determinations. Acknowledgements I would like to thank the crew and participants in the CEEMEX cruises, particularly the cruise leader Dr. A. van der Heiden, for their cooperation. This research was sponsored by the DG XII of the EU (Contracts TS2.0213.E and CI1.0431.E) and by the Spanish DGCICYT (Ref. CE89-0006). B. Lynas translated the Spanish text.

References Acal DE, Arias A (1990) Evaluaci6n de los recursos demersopel~igicos vulnerables a redes de arrastre de fondo en el sur del Pacffico de M6xico. Ciencs mar 16(3):93-129 Arvizu-Marffnez J (1987) Fisheries activities in the Gulf of California, Mexico. Rep Calif coop ocean Fish Invest (CalCOFI) 28:32-36 Bakun A, Beyer J, Pauly D, Pope JG, Sharp J D (1982) Ocean science in relation to living resources. Can J Fish aquat Sciences 39:1050-1070 Beverton RJH, Holt RJ (1957) On the dynamics of exploited fish populations. Fishery Invest, Lond (Ser 2) 19:1-237 Bianchi G (1991) Demersal assemblages of the continental shelf and slope edge between the Gulf of Tehuantepec (Mexico) and the Gulf of Papagayo (Costa Rica). Mar Ecol Progr Ser 73:121-140 Blackburn M (1962) An oceanographic study of the Gulf of Tehuantepec. Spec scient Rep US Fish Wildl Serv (Fisheries) 404:1-28 Blackburn M (1966) Biological oceanography of the Eastern tropical Pacific: summary of existing information. Spec scient Rep US Fish Wildl Serv (Fisheries) 540:1-18 Brey 1".,Pauly D (1986) Electronic length frequency analysis. A re9~i~ed and extended user's guide to ELEFAN 0, 1 and 2. Ber Inst MeeresKde Kiel 149:1-76 Castro-Aguirre JL, Arvizu-Martinez J, Paez-Barrera J (1970) Contribuci6n al conocimiento de los peces del Golfo de California. Revta Soc mex Hist nat 31:107-181

ChSvez H, Ramos-Padilla R (1974) Informe de las actividades de pesca exploratoria efectuadas con el barco "Louis Caubribre" en aguas nacionales del Pacffico durante 1968-1969. Instituto Nacional Pesca, Serie infmv Inst nac Pesca, M6xico 122:1-30 Elorduy JF (1993) Edad y erecimiento, reproducci6n y habitos alimenticios de dos especies simpatricas del genero CaulolatiIus Gill 1863, de la Bahia de la Paz y ~reas adyacentes. Ph.D. manuscript. Euskal Herriko Unibertsitatea, Bilbao, Spain (Mimeo) Fiedler PC (1992) Seasonal climatologies and variability of eastern tropical Pacific surface waters. NOAA natn mar Fish Serv tecb Rep US Dep Commerce 109:1-65 Gayanilo FG, Soriano M, Pauly D (1988) A draft guide to the complete ELEFAN. SOFTWARE Ser. 2. Center for Living Aquatic Resources, Manila Hasselblad V (1966) Estimation of parameters for a mixture of normal distributions. Technometrics 8:431-444 Heiden van der AM (1985) Taxonomfa, biologfa y evaluaci6n de la ictiofanna demersal del Golfo de California. In: Yafiez-Arencibia A (ed) Recursos pesqueros potenciales de M6xico: la pesca acompafiante del camar6n. Programa Universitario de Alimentos, Instituto Ciencias Mar Limnologfa, Instituto Nacional Pesca, Universidad Nacional Aut6noma M6xico, M6xico DF, pp 149-200 Heiden van der AM, Findley LT (1988) Lista de los peces marinos del sur de Sinaloa, Mdxico. An Inst Ciencs Mar Limnol, Univ nac aut6n M6xico 15:209-224 Heiden van der AM, Findley LT, Rodriguez-Cajiga S, Hendrickx ME (1982) Inventario de los peces marinos y de lagunas costeras de] sur de Sinaloa, M6xico. In: Heiden van der AM, Hendrickx ME (eds) Inventario de la fauna marina y costera del sur de Sinaloa, M6xico. Instituto Ciencias Mar Limnologia, Universidad Nacional Auton6ma M6xico, Mazatlan, M6xico, pp 76-96 (Mimeo) Longhurst AR, Panly D (1987) Ecology of tropical oceans. Academic Press Inc, London MacDonald PDM, Pitcher TJ (1979) Age-groups from size-frequency data: a versatile and efficient method of analyzing distribution mixtures. J Fish Res Bd Can 36:987-1001 Manooch, III, C. S. (1987) Age and growth of snappers and groupers. In: Polovina JJ, Ralston S (eds) Tropical snappers and groupers. Biology and fisheries management. Westwiew Press, Boulder, Colorado, pp 329-374 Mathews CE Granados JL, Arvizu J (1974) Results of the exploratory cruises of the "Alejandro de Humboldt" in the Gulf of California. Rep C alif coop ocean Fish Invest (CalCOFI) 17:101111 Mohr E (1921) Alterbestimmung bei tropischen Fischen. Zool Anz 53:87-95 Morales-Nin B (1989) Growth determination of tropical marine fishes by means of otolith interpretation and length frequency analysis. Aquat living Resour (Nantes) 2:241-253 Morales-Nin B (1992) Determinaci6n del crecimiento de los ostefctios tropicales por medio del anfilisis de frecuencia de tallas y de la microestructura de los otolitos. FAO Fish tech Pap 322:1-58 Morales-Nin B (1993) First biological data on Synodus evermanni Jordan and Bollman, 1890 (Pisces: Synodontidae) from the central Mexican Pacific. Scientia mar 57:95-99 Munro JL, Pauly D (1983) A simple method for comparing the growth of fishes and invertebrates. Fishbyte 1:5-6 Pauly D (1979) Gill size and temperature as governing factors in fish growth: a generalization of von Bertalanffy's growth formula. Ber Inst MeeresKde Kiel 63:1-156 Pauly D (1984) Fish population dynamics in tropical waters, a manual for use with programmable calculators. Stud Rev int Cent living aquat Resour Mgmt, Manila 8:1-23 Pauly D, David N (1981) ELEFAN I, a BASIC program for the objective extraction of growth parameters from length-frequency data. Meeresforsch Rep mar Res 28:205-211 (Bet dt wiss Kommn Meeresforsch) Petersen CG (1891) Eine Methode zur Bestimmung des Alters and Wuchses der Fische. Mitt dt SeefischVer 11:226-235

217 Plascencia-Gonz~ilez HG (1993) Contribuci6n al conocimiento de las comunidades de peces asociados a los fondos blandos de la plataforma continental del sur de Sinaloa, M6xieo (Proyecto SIPCO). Tesis Master en Ciencias. Facultad Ciencias, Universidad Nacional Aut6noma de Mdxico, Mdxico DF Poinsard F, Troadec JP (1966) D6termination de l'age par la lecture des otolithes chez deux espbces de sciaenid6s Ouest-Africains (Pseudotolithus senegalensis C.V. et Pseudotolithus typus). J Cons perm int Explor Mer 30:291-307 Schnute J, Fournier D (1980) A new approach to length frequency analysis: growth structure. Can J Fish aquat Sciences 37:13371351 Stromme T, Saetersdal G (1988) Surveys of the fish resources on the Pacific shelf from Colombia to Southern Mexico, 1987. Reports on surveys with R/V "Dr. F. Nansen". Vols. 1 ~md 2. Institute of Marine Research, Bergen, Norway

Thomson DA, Findley LT, Kerstitch AN (1987) Reef fishes of the Sea of Cortez. 2rid edn. University of Arizona Press, Arizona Walker B (1960) Distribution and affinities of the marine fish fauna of the Gulf of California. Syst Zo61 9:123-133 Wetherall JA, Polovina JJ, Ralston S (1987) Estimating growth and mortality in steady-state fish stocks from length-based frequency data. Proc 13th int Center living aquat Resour Mgmt (ICLARM) Conf 13:53-74 [Pauly D, Morgan GR (eds) International Center for Living Aquatic Resources Management, Manila, Philippines] Wyrtki K (1966) Oceanography of the eastern equatorial Pacific Ocean. Oceanogr mar Biol A Rev 4:33-68 Wyrtki K (1967) Circulation and water masses in the Eastern Equatorial Pacific Ocean. Int J Oceanol Limnol 1:117-147