Distribution and Abundance of Scombrid Larvae in Southern Brazilian Waters

BULLETINOF MARINESCIENCE,31(4): 824-832. 1981

DISTRIBUTION AND ABUNDANCE OF SCOMBRID LARVAE IN SOUTHERN BRAZILIAN WATERS

Yasunobu Matsuura and Gosuke Sato

ABSTRACT Distribution and abundance of scombrid larvae in southern Brazilian waters (23°S-29"S) are reported from plankton samples taken during the period between November ]975 and October ]976. Five species were identified: Auxis sp., Euthynnus al/etteratus, Scomber japonicus, Katsuwonus pelamis and Thunnus alalunga. Among them Sc'omber japonicus spawned in winter and spring, especially in January, while the other four species spawned in spring and summer. The most abundant larvae were Auxis sp., which were collected from the entire study area. The distribution of Euthynnus alletteratus larvae was mainly coastal. Auxis larvae less than 12 mm standard length showed no catch ratio difference in day and night hauls.

Among previous studies on the occurrence of scombrid larvae from the Bra- zilian waters, Richards (1969a,b) reported on the larvae of Thunnus albacares, T, alalunga, T. obesus, T. thynnus and Katsuwonus pelamis from the equatorial Brazilian coast. Aboussouan (1969) showed a larval tuna from Brazilian waters, but it was not identified. Nishikawa et al. (1978) depicted the seasonal occurrences of Thunnus alalunga, T. obesus, T. albacares and Katsuwonus pelamis along the Brazilian coast. These survey cruises conducted by the foreign research vessels were made mainly in the open seas. In our studies we investigated distribution and abundance in the coastal waters and seasonal variation of the scombrid larvae, using the materials taken during the FINEP (Finaciadora de Estudos e Projetos S.A.) program in southern Brazil. The larvae of five species of the family Scombridae were identified: Scomber japonicus, Auxis sp., Thunnus alalunga, Euthynnus alletteratus and Katsuwonus pelamis. Because of abundant number of Auxis larvae we were able to discuss night/day catch ratio of this species.

MATERIAL AND METHODS

Plankton samples were made with a Bongo net sampler from R/V PROF. W. BESNARDduring four cruises conducted in November-December 1975, January, May and September-October in 1976. Each cruise covered the same survey area between Cabo Frio (23°S) to the south of Cabo de Santa Marta Grande (29°S), in which transects of ]40 oceanographic stations were designated (Fig. I). Distance between stations was 20 nautical miles. At each station routine hydrographic observation and standard oblique hauls with Bongo nets were made. Plankton hauls were double oblique from within 5 m of bottom to surface or from 200 m depth to surface at deep stations. The ship speed was about 2 knots and wire angle was adjusted to maintain 45° during tow. No net depth recorder was used and the maximum depth of net was estimated from wire angle and length, The sampling method and procedure to process the material followed the recommendation of Ahlstrom et al. (1973) and Kramer et al. (1972). All fish eggs and larvae were sorted from plankton samples, then scombrid larvae were separated from the rest. Identification of larvae was made based on the following papers: Scomber japonicus: Berrien, ]978; Katsuwonus pelamis, Thunnus alalunga, Euthynnus al/ettera/Us and Auxis sp.: Mat- sumoto, 1958; 1959; Matsumoto et aI., 1972. The systematic status of Atlantic Auxis is still problematic, therefore we used the name Auxis sp. for this group. The number of larvae taken at each station was transformed into the number per 10 m2 of sea surface using the following expression:

824 MATSUURA AND SATO: BRAZILIAN SCOMBRID LARVAE 825

STATION PLAN 2YS o

o 0 o~ _.0 ,. ~..•." \ ... ,,' 0 o o o o o o , o o o 0, o o 0 o o o 0

o 0 / o o o o o "" 1:1- - - o o , 0 o o , ,0 o o p' 0,' t I o lorionopoliS o , 1 o ", 0' [ ':abO de St , 0 arta Grand 0' o ,f 0 o o 290

49° 48° 47° 46° 45° 44° 43° 42° 41° 40"

Figure I. Stations occupied by R/V PROF. W. BESNARD during four survey cruises made in 1975 and 1976. Each cruise comprised 140 oceanographic stations in the region between Cabo Frio (23°S) and Cabo de Santa Marta Grande (29°S).

d·x Y=--·10, v where, y = number of standarized larvae per 10 m2 of sea surface x = number of larvae taken at station d = maximum depth of the haul (m) v = volume of water filtered (m3) measured by flow meter.

DISTRIBUTION AND RELATIVE ABUNDANCE The proportion of scombrid larvae in relation to total fish larvae showed the highest value of 3.02% on the January 1976 cruise and the lowest of 0.01% on the May 1976 cruise. Total number of scombrid larvae from all four cruises indicated a seasonal fluctuation for each species (Fig. 2). Larvae of Scomber japonicus were most abundant in spring (September to October) and were probably the result of winter spawning. All other scombrid larvae reached their peak abundance in summer (January). Spatial and temporal distributions of individual species are presented in the following accounts. Auxis sp.-Within the family Scombridae, larvae of Auxis were the most abundant (Table l) but they were collected from only two cruises (late spring and summer seasons). During the cruise of November-December 1975, Auxis larvae were taken from all surveyed areas except from the coastal stations (Fig. 3a). Most of the larvae 826 BULLETIN OF MARINE SCIENCE, VOL. 31, NO.4, 1981

B 'm 462

~ ~

150 o > oL '0 100

L .0 E :> c 50

SAEKT 0 S AE K TO MAY' 76 SEP-OCT' 76

E2l S = Scomber []] K= Katsuwonus I2l A= Auxis f.1l':i\!I T= Thunnus • E= Euthvnnus o 0= Others not identified Figure 2. Number of all larval scombrid species collected during four survey cruises of the FINEP program, were collected between Santos (24°S) and Paranagua (25°S) in the depth zone between 50 m and 200 m. They were also taken from waters off the continental shelf. During the cruise of January 1976 (Fig. 3b), Auxis larvae were common throughout the surveyed area, including the coastal region. Two high concentration areas of larvae were located between Ilha Grande and Ilha de Sao Sebastiao

Table 1. Number of scombrid larvae collected with Bongo net

Average Number Number of Percent of Number of Number of of Positive Positive Standardized Larvae per Species Stations Stations Stations Larvae Station Cruises

Auxis 280 112 40,0% 3,486.20 31.13 Nov.-Dec. '75 Jan. '76 Euthynnus 280 17 6.1% 211.27 12.43 Nov.-Dec. '75 Jan. '76 Scomber 420 35 8.3% 1,368.80 39.11 Nov.-Dec. '75 Jan. '76 Sep,-Oct. '76 MATSUURA AND SATO: BRAZILIAN SCOMBRID LARVAE 827

JANUA RY 1976 ,.:c>r···· ...... e. '.~.• / • • • • e. _ ' • ••••••• 'e" '. • • .'.· . ': • . ....•/ . .' ....•.~~' . . , '. . ,' · , " ... :.•' .. ·.. . .•..•...... '.e • ,:' Auxis sp .. ~sp ' 2 •... 2 nl? of larvae/10m ...... n"" of larvae 110m ••••••. , . · a ... · a . • I - to · ." • I - 10 • • \I - 50 .' • II - 50 • •• • - • ~I . .. • 51 - 100 . I . ,. . ~' • 51 - 100 '..~,... .::> 100 lL _~. . ',. .. • > 100

Figure 3. Distribution of AI/xis sp. larvae in southern Brazilian waters collected during the FINEP program in November to December 1975 (a) and January 1976 (b). Each circle indicates number of larvae under 10 m2 of sea surface. and another between Paranagmi and Sao Francisco do SuI (26°10'S), both in the depth zone between 50 m and 200 m. Scomber japonicus.-The highest concentration of S. japonicus larvae was observed during the cold season (September-October 1976). Few larvae were taken from November to January (Figs. 2 and 4a). During the September-October 1976 cruise, higher concentrations of larvae were located in three areas: Cabo Frio, I1ha Grande and Cabo de Santa Marta Grande (Fig. 4b). During the November- December 1975 cruise, fewer larvae were collected at four offshore stations near Cabo Frio (Fig. 4a) and in the January 1976 cruise, Cabo Frio region had the only occurrences of S. japonicus larvae. In the Santa Catarina region, S. japonicus larvae were collected on two cruises (from September to December), but in the Cabo Frio region the persistent occurrences of them were observed on three cruises (from September to January). Probably these two spawning groups belong to different origins. However to confirm this supposition, it is necessary to make an extended survey cruise in an enlarged survey area.

NOV DEC :975 SEP - OCT 1976 . e:;.. . • ••. JANUARY 976 Q · :.".... '..~::.: .'. :..~ "

·, . ','" - .. '.' ;' '. Scomber iODOnicu$ · ~ jODonicus 2 no.of larvae/10m noof larvae/10m " a . · a • I - 10 NOV·DEC. i • I - 10 . ~• • II-50 1975 • II - 50 .51 - 100 o I - 10 JANUARY I. a II-50 1976 I • > 100

Figure 4. Distribution of Scomber japonicl/s larvae in southern Brazilian waters collected during the FINEP program. 828 BULLETIN OF MARINE SCIENCE, VOL. 31, NO.4, 1981

NOV-DEC 1975 JANUARY 1976 JANUARY 1976 o , • •••• ~'.' J .. ~.~. " -: • • .~:, J ~':., ~ ... " ... '. ., . ., . "

.. " ~:,,' . '.' . ,. no. of larvae 110m2 ~~ 2 · 0 nO. of larvae/IO m • 1- 10 1l!!.1!!nY! · 0 • 11- 50 Thumus • 1 - 10 JAN76 o I - 10 KotsuwOf1JS • II - 50 JAN 76 . :./" o I - 10 N·07S

Figure 5. Distribution of larvae Euthynnus alletteratus (a), Katsuwonus pelamis and Thunnus sp. (b) in southern Brazilian waters from November 1975 to January 1976.

Euthynnus alletteratus .-Occurrences of Euthynnus alletteratus (Fig. 5) were much fewer than those of Auxis sp. (Table 1). During the November-December 1975cruise, only one larva was collected from the offshore station near Cabo Frio. Occurrences of E. alletteratus larvae in the January 1976 cruise were concen- trated in coastal stations. During the summer season, it is common to see schools of E. alletteratus in the region between Ilha Grande and Paranagua near islands or peninsulas. This may suggest that E. alletteratus prefers to spawn close to the shore facing open water. A similar phenomenon was observed with Eythynnus lineatus in the eastern Pacific (Klawe, 1963). Katsuwonus pelamis.-Two larvae of Katsuwonus pelamis were collected in the January 1976 cruise: one at the offshore station of Cabo Frio and another at Sao Francisco do SuI (Fig. 5b). Thunnus sp.-All tuna larvae were collected from three offshore stations within the warm Brazil current during the January 1976 cruise. Of the eleven tuna larvae, only one specimen was identified as Thunnus alalunga. The other spec- imens were too small to accurately identify.

TEMPERATURE AND SALINITY Larvae of tunas and billfishes were known to be distributed in the upper mixed layer, therefore we took temperature and salinity measurements from 10 m depth at each station to represent the hydrographic conditions of the surface layer. Salinities and temperatures of all positive stations were plotted in 95% confidence limits for three species (Fig. 6). Larvae of Sc'omber japonicus were collected from temperature range from 20.4 to 24.2°C and salinity range from 34.02 to 37.29%0. Studying the spawning areas of Scomber species from the northwestern Atlantic, Berrien (1978) showed that the spawning of S. japonicus was observed in offshore waters south of Cape Hatteras during winter and spring seasons and the larvae occurred in water temperature between 16.0 and 29.4°C. The occurrence of S. japonicus larvae from southern Brazilian waters showed similar spawning season. Larvae of Euthynnus alletteratus were collected from the coastal low salinity MATSUURA AND SATO: BRAZILIAN SCOMBRID LARVAE 829

(Oe) (%0

38 N=I/2 N=35 N= 16 28 37 26

36 w 24 0:: ~ >- 35 f- 22 f- « Z 0:: 34 w 20 -l t + a.. « (f) ~ w 18 33 f-

32 16

Auxis Scomber Euthvnnus Figure 6. Temperature and salinity ranges of positive stations in which scombrid larvae were taken. In each sample, the crossbar indicates the mean, the hollow rectangle shows a range of standard deviation on each side of the mean and the black rectangle shows 95% confidence limits of the mean. waters which ranged from 34.34 to 35.92%0 with mean salinity 35.12%0. The mean temperature of 25.1°C was the highest found for the three species. Temperature and salinity ranges of Auxis sp. larvae varied considerably. How- ever most of the samples were collected within the temperature range from 22.8 to 26.4°C and salinity range from 35.51 to 36.55%0. The offshore spawner Auxis sp. showed the highest mean salinity (35.93%0) of the three species. The mean temperature and salinity at 10 m depth recorded for Katsuwonus pelamis stations were 25.9°C and 36.73%0 respectively and those for Thunnus sp. were 25.8°C and 36.71%0 respectively.

NIGHT/DAY CATCH RATIO In order to calculate the night and day (N/D) catch ratio, the average number of larvae per positive station in which scombrid larvae were taken was used (Table 2). Samples collected from 06:00 to 18:00 were considered as day-time samples and the rest were night-time samples. The N/D catch ratio of Auxis

Table 2. Night/day catch ratio of scombrid larvae collected with Bongo net

Day (D) Night (N)

Number of Number Number of Number of Number Number of Positive of Larvae per Positive of Larvae per Species Stations Larvae Station Stations Larvae Station NID Cruises

Auxis 54 57] 10.57 58 585 10.08 0.95 Nov.-Dec. '75 Jan. '76 Eulhynnus 6 39 6.5 11 54 4.91 0.76 Nov.-Dec, '75 Jan. '76 Scomber 12 180 15.00 23 308 13.39 0.89 Nov.-Dec. '75 Jan. '76 Sep.-Oct. '76 830 BULLETIN OF MARINE SCIENCE. VOL. 31. NO.4. 198\

200

180 1 160 • NIGHT HAUL 140 w « o DAY HAJ'-. > 120 0: « ..J 100 , "-0 80~ 0: w (I) 601 :;;; ::J Z 40':

-----J~ 2 3 4 5 6 7 8 9 10 II 12 13 '4 IS 16 /7 18.5 STANDARD LENGTH (mm) Figure 7. Size frequency of AI/xis larvae taken during day and night times.

larvae was 0.95 and those of Euthynnus and Scomher were 0.76 and 0.89 respectively. All values were less than one, which means that the larval catch during day-time exceeded that of the night-time. Auxis larvae were collected from most of the surveyed area and the proportion of positive stations of two cruises was 40% (Table 1). Because the N/D catch ratio of Auxis larvae showed the value near 1.0, we used the Mann-Whitney U- test (Siegel, 1956) to determine the probability of equal catch in day and night hauls. For a rank test, we used all positive and negative stations which showed the temperature and salinity within range of mean values ± 1 standard deviation. These temperature-salinity ranges are taken from the present study (Fig. 6), hav- ing temperature range from 22.8 to 26.4°C and salinity from 35.3 to 36.6%0. The probability of equal catch in day and night hauls was 0.19 (z = 0.876), thus we can accept the null hypothesis that there is no difference in diurnal catch of Auxis larvae. With regard to the N/D catch ratio of Auxis larvae, some papers demonstrated no difference (Wade, 1951; Klawe et al., 1970) while others showed more catch in night-time collection (Strasburg, 1960; Matsumoto, 1958; Klawe, 1963; Rich- ards and Simmons, 1971). Length frequencies of Auxis larvae taken in day and night (Fig. 7) show there is no difference between day and night hauls in smaller fish up to 12 mm SL. However from this size up, night hauls caught larger larvae more frequently. Since our tows were made obliquely, collecting all depth layers, the difference observed in larger larvae seems to prove the occurrence of a net avoidance during day-time. Similar results were observed by Richards and Simmons (1971) for larger larvae of Auxis sp. from southeastern Atlantic.

CONCLUSIONS Of five species identified from the southern Brazilian waters, larvae of Auxis sp. was the most abundant. This suggests that there is a large Auxis stock in this region, but it is difficult to estimate a population size through larval abundance. MATSUURA AND SATO: BRAZILIAN SCOMBRID LARVAE 831

Our stations did not cover the entire range which is essential for estimating stock size. Further investigation of the stock abundance of this species will be rec- ommended. The other two abundant species were Scomber japonicus and Euthynnus alletteratus. Larvae of Thunnus and Katsuwonus were few, mainly due to small number of stations beyond the continental shelf. Occurrences of larvae of the three abundant species showed fairly good seg- regation of time and space. During the summer season, Auxis larvae occurred predominantly over the outer half of the continental shelf where high saline tropical water predominates, whereas Euthynnus alletteratus larvae were found main- lyon nearshore stations or around islands where the mean salinity of stations was low. From the present data we cannot determine whether they prefer to spawn around the land mass or in coastal low saline waters. The larvae of Scomber japonicus were found mainly in the cold season and probably there are two separated spawning stocks; one in the Cabo Frio region and one in the Santa Catarina region.

ACKNOWLEDGMENTS

This project was initiated as part of an integrated oceanographic investigation of the southern Brazilian coast by Instituto Oceanognifico da Universidade de Sao Paulo with financial support of FINEP (Financiadora de Estudos e Projetos S. A.) and OEA (Organiza~ao dos Estados Americanos). Assistance was provided by many people and agencies. Special thanks go to Dr. L. N. Chao of the Funda~ao Universidade do Rio Grande and Dr. W. J. Richards of the National Marine Fisheries Service, for revision and critical reading of the manuscript. This paper was presented at the 1978 SCRS meeting of ICCAT in Madrid.

LITERA TURE CITED

Aboussouan, A. 1969. Sur une petite collection de larves de Teleosteens recoltee au large du Bresil (Campagne "Calypso" 1962). Vie et Milieu 20: 595-610. Ahlstrom, E. H., K. Sherman, and P. E. Smith. ]973. Seagoing operation in ichthyoplankton surveys. FAO Fish. Tech. Paper 122: 14-26. Berrien, P. L. 1978. Egg and larvae of Sc'omber scombrus and Scomber japonicus in the continental shelf waters between Massachusetts and Florida. Fish. Bull. U.S. 76: 95-115. Klawe, W. L. 1963. Observation on the spawning of four species of tuna (Neothunnus macropterus, KatsulI'onlis peJamis, Auxis thazard and Elithynnlls lineatus) in the eastern Pacific Ocean, based on the distribution of their larvae and juveniles. Bull. Inter-Am. Trop. Tuna Comm. 6: 447-450. --, J. J. Pella, and W. S. Leet. 1970. The distribution, abundance and ecology of larval tunas from the entrance to the gulf of California. Bull. Inter-Am. Trop. Tuna Comm. 14: 505-544. Kramer, D., M. J. Kalin, E. G. Stevens, J. R. Thrailkill, and J. R. Zweiffel. 1972. Collecting and processing data on fish eggs and larvae in the California current region. U.S. Dept. Commerce, NOAA Tech. Rep. NMFS Circ. 370. 38 pp. Matsumoto, W. M. 1958. Description and distribution of larvae of four species of tuna in Central Pacific waters. Fish Bull., U.S. Fish Wildl. Servo 58: 31-72. --. 1959. Description of Euthynnus and Auxis larvae from the Pacific and Atlantic oceans and adjacent seas. Dana Report, 50. 35 pp. --, E. H. Ahlstrom, S. Jones, W. L. Klawe, W. J. Richards, and S. Ueyanagi. 1972. On the clarification of larval tuna identification particularly in the genus Thunnus. Fish. Bull., U.S. 70: 1-12. Nishikawa, Y., S. Kikawa, M. Honma, and S. Ueyanagi. 1978. Distribution atlas of larval tuna, billfishes and related species. Results of ]arval surveys by R/V Shunyo-Maru, and Shoyo-Maru, 1956-1975. Far Seas Fish. Res. Lab., S. Ser. 9: ]-99. Richards, W. J. ]969a. Tropical Atlantic tuna larvae collected during Equalant surveys. U.S. Fish Wildl. Serv., Comm. Fish. Rev. 31: 33-37. --. ]969b. Distribution and relative apparent abundance of ]arval tunas collected in the tropical Atlantic during Equalant surveys 1 and II. Proc. Symp. on Oceanography and Fish. Resources of the Tropical Atlantic. Pp. 289-315. 832 BULLETIN OF MARINE SCIENCE, VOL 31, NO, 4,1981

---, and D. C. Simmons, 1971. Distribution of tuna larvae (Pisces, Scombridae) in the northwestern Gulf of Guinea and Sierra Leone, Fish, Bull., U. S. 69: 555-568. Siegel, S. 1956. Nonparametric statistics for the behavioral sciences, McGraw-Hili Book Company, Inc., New York. 312 pp. Strasburg, D, W, 1960, Estimates of larval tuna abundance in the central Pacific. Fish. Bull., U.S. Fish WildL Serv, 60: 231-255, Wade, C. B. 1951. Larvae of tuna and tuna-like fishes from Philippine waters, Fish, Bull., U,S, Fish Wild!. Servo 51: 445-485.

DATE ACCEPTED: January 2, 1980,

ADDRESSES: lnstituto Oceanografico, Universidade de Siio Paulo, Cidade Universitaria, Butan/ii, Siio Paulo, Brasil,