Reproductive Cycle of the Pacific Bonito, Sarda Chilensis (Scombridae), from Northern Chilel

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Reproductive Cycle of the Pacific Bonito, Sarda chilensis (Scombridae), from Northern Chilel

STEPHEN R. GOLDBERG 2 AND DONALDa MUSSIETT C.3

ABSTRACT: The Pacific bonito, Sarda chilensis, spawns from spring to late summer off northern Chile. The smallest female in spawning condition was 410mm standard length (SL); the smallest spermiogenic male, 390mm SL. Females spawn more than one batch of eggs per season.

THE PACIFIC BONITO, Sarda chilensis, occurs in Ovaries were histologically classified into the Pacific from Chile to the Gulf of Alaska four stages (sizes are mean diameters) (Table (Miller and Lea 1976). Previous studies have 1): regressed or regressing (contain primary given the spawning time for S. chilensis oocytes [56 !lm] or mature oocytes undergoing in Chile (Barrett 1971, Serra et al. 1980) atresia); previtellogenic (contain enlarging and Peru (Chirinos de Vildoso 1966) as [161 !lm] oocytes with a ring of vacuoles October-November and ending before April. around the inner periphery); vitellogenic (en However, as these observations were based on larging oocytes [315 !lm] in the process of gonosomatic indices or microscopic examina accumulating yolk); spawning (mature, yolk tions of unstained gonads, it was felt that a filled oocytes [545 !lm] and/or hydrated eggs histological analysis of monthly samples (as [798 !lm]). presented herein) would give a more precise Testes (Table 2) were histologically classi description of the reproductive cycle of this fied into four stages: spermiogenesis (lumina species. occluded with sperm, germinal cysts line lumina); late spermiogenesis (lumina oc cluded with sperm, reduced quantities of ger MATERIALS AND METHODS minal cysts); regression (germinal cysts ex hausted); and recrudescence (proliferation of A total of 129 females and 169 males were obtained from local fishermen at Iquique germinal cysts). (20°18' S, 70°08' W), region I, Chile from November 1981 to December 1982. Fish were collected with nets. Gonads were preserved in RESULTS 10 percent formalin. Histological sections of Gonosomatic indices increased (Figure I) 85 females and 102 males were cut at 8 !lm and stained with Harris' hematoxylin followed by during spring (September in southern hemi sphere) and reached a maximum in early sum eosin counterstain. Fresh fish and gonads mer (December). The smallest female in were weighed to the nearest gram using a tor sion balance. Seasonal gonosomatic indices spawning condition measured 410mm stan (GSI) (gonad wt/fish wt x 100) were cal dard length (SL). The earliest postovulatory follicles were observed in September 1982. culated. Fish weight in these calculations in cluded the gonads. These structures are remnants of the granu- losa layer of the spawned eggs which hyper trophy. In Sarda chilensis they are highly con 1 Manuscript accepted II April 1984. voluted structures consisting of a layer of 2 Whittier College, Department of Biology, Whittier, columnar epithelium and an underlying sup California 90608. portive connective tissue theca. From spawn 3 Instituto Profesional de Iquique, Casilla 121, Serrano 579, Iquique, Chile. Current Address (DMC) Casilla 379, ing the northern anchovy, Engraulis mordax, in Copiapo, Chile. captivity (Leong 1971) and from subsequent 228 Reproductive Cycle of Pacific Bonito-GoLDBERG AND MUSSIETI C. 229

TABLE 1 MONTHLY DISTRIBUTION OF BODY SIZES (SL) AND STAGES IN Sarda chilensis SPAWNING CYCLE, NOVEMBER 1981-DECEMBER 1982

REGRESSED RANGE OR REGRESSING PREVITELLOGENIC VITELLOGENIC SPAWNING MONTH N (mm) (%) (%) (%) (%)

November 2 430-480 0 0 0 100 December 5 410-510 0 0 0 100 January 5 410-430 20 0 0 80 February 4 410-480 0 25 0 75 March 11 425-550 55 9 0 36 April 7 425-550 100 0 0 0 May 5 415-460 100 0 0 0 June 9 420-455 100 0 0 0 July 7 425-530 100 0 0 0 August 6 420-450 100 0 0 0 September 6 420-570 33 0 0 67 October 10 425-580 0 20 20 60 November 6 415-490 0 0 0 100 December 2 460-480 0 0 0 100

TABLE 2 MONTHLY DISTRIBUTION OF BODY SIZES (SL) AND STAGES IN Sarda chilensis TESTICULAR CYCLE, NOVEMBER 1981-DECEMBER 1982

LATE RANGE REGRESSION RECRUDESCENCE SPERMIOGENESIS SPERMIOGENESIS MONTH N (mm) (%) (%) (%) (%)

November 8 385-455 0 0 100 0 December 6 415-495 0 0 83 17 January 15 390-460 0 0 80 20 February 12 400-465 0 0 67 33 March 10 425-455 30 0 70 0 April 7 425-550 100 0 0 0 May 4 425-560 100 0 0 0 June 6 425-445 100 0 0 0 July 7 420-445 100 0 0 0 August 4 430-480 25 50 25 0 September 7 440-525 0 14 86 0 October 8 420-515 0 0 100 0 November 5 410-465 0 0 100 0 December 3 485-600 0 0 100 0 histological analysis of material obtained in a subsequent spawning indicated S. chilensis this manner (Hunter and Goldberg 1980), it spawns more than once during a reproductive was determined that the postovulatory follicle season. In some cases hydrated eggs were also has a brief existence and is indistinguishable noted. Hydration occurs just prior to spawn from atretic follicles after 48 hrs. They were ing when the mature oocyte grows to as much noted in 61 percent of1981-1982 females that as four times its original volume (Wallace and were classified as being in spawning condition. Selman 1981). The presence ofpostovulatory follicles from a At the end of summer (1981-1982) gono recent spawning alongside mature follicles for somatic indices decreased (Figure 1). During 230 PACIFIC SCIENCE, Volume 38, July 1984

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(II) (5) (25) f 5 (8) r) >- o (2) J o 60 m f-" 5 4.0 o ~

O'------,---,----,------,.--+-----"'''-,------'=,--=,-----'''''-,--=--,----,-----,----,--r---

MONTH

FIGURE L Seasonal gonosomatic indices for Sarda chi/ensis. Vertical line = range; horizontal line = mean; rectan gle = 95 percent confidence interval; white rectangle female, black rectangle male; sample size in parentheses.

March, females undergoing atresia comprised abundant. It differs from the prolonged 27 percent of our sample. This is commonly spawning cycles typical of tropical and sub seen toward the end of the spawning cycle tropical species (Nikolsky 1963) in which when follicles that initiated but did not com there is no clear seasonal abundance in the plete yolk deposition degenerate. All ovaries plankton on which larvae feed. from April-August were regressed (Table 1). Previous work in Chile (Barrett 1971, Serra The data for September-December 1982 were et al. 1980) based on analyses ofgonosomatic similar to those from 1981. In 1982, the ab indices indicated that spawning begins in Sep sence ofprevitellogenic and vitellogenic stages tember and ends before April. Our work his (which normally precede spawning) can prob tologically confirms their observations. Bar ably be explained by our small August sample rett (1971) found that female Sarda chilensis size. of approximately 51 em (fork length) were The gonosomatic indice data for males mature. Our smallest mature female (41Omm (Figure 1) was similar to that for females as SL) had a total length of 485 mm, making it was the seasonal pattern oftestes stages (Table somewhat smaller than Barrett's (1971) 2). Testes sizes were largest during late estimate. spring-early summer, followed by a size de Klawe (1961) summarized the dates of crease through summer. Testes began to en Sarda chilensis spawning observations from large in late winter (August). The smallest other areas ofthe world. In all cases, spawning reproductively active male (spermiogenesis in occurred during summer. The only exception progress) measured 390 mm SL. came from Dakar, Senegal, where spawning was recorded during February-March.

DISCUSSION In northern Chile, Sarda chilensis under goes a seasonal reproductive cycle typical of ACKNOWLEDGMENTS temperate zone fishes, as spawning occurs We thank Marie C. Pizzorno for assistance during half of the year with no reproductive in histology and data analysis. This study was activity in the other half. This type of cycle is aided by a Whittier College Faculty Research timed so that larvae appear when food is Grant. Reproductive Cycle ofPacific Bonito-GoLDBERG AND MUSSIETT C. 231

LITERATURE CITED LEONG, R. 1971. Induced spawning of the northern anchovy, Engraulis mordax Gir BARRETT, I. 1971. Preliminary observations ard. Fish. Bull. (U.S.) 69: 357-360. on the biology and fishery dynamics of the MILLER, D. J., and R. N. LEA. 1976. Guide to bonito (Sarda chilensis) in Chilean waters. the coastal marine fishes of California. Bol. Cient. Inst. Fom. Pesq., Santiago, Calif. Dep. Fish Game, Fish. Bull. 157.249 Chile 15:1-55. pp. (Rev. publ. by Div. Agric. Sci., Univ. CHIRINOS DE VILDOSO, A. 1966. Estudios Calif. Richmond). sobre la reproduccion del "bonito" Sarda NIKOLSKY, G. V. 1963. The ecology of fishes. chilensis (c. y V.) en aguas adyacentes a la Academic Press, New York, 352 pp. costa peruana. Min. de Agric. (Peru), Servo SERRA B., J., O. ROJAS J., F. INOSTROZA C., Div. Cient. 14 (2a. Ed.) 75 pp. y J. CANON C. 1980. Sinopsis biologica HUNTER, J. R., and S. R. GOLDBERG. 1980. del bonito fecundit~ (Sarda sarda chilensis) Spawning incidence and batch in (Teleostomi, Perciformes, Scombridae). northern anchovy, Engraulis mordax. Fish. Rev. Com. Perm. Pacifico Sur II :423-434. Bull. (U.S.) 77:641-652. WALLACE, R. A., and K. SELMAN. 1981. Cel KLAWE, W. L. 1961. Notes on larvae, juveniles lular and dynamic aspects ofoocyte growth and spawning of bonito (Sarda) from the in teleosts. Amer. Zool. 21: 325-343. eastern Pacific Ocean. Pac. Sci. 15 : 487-493.