by
N. E. BRUNETTI and M. L. IVANOVIC
Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP). C.C. 175, Mar del Plata, 7600 - Argentina (e-mail: brunetti@inidep.ed.ar)
Summary
The purpose of this account is to update the current knowledge on several aspects of the species reproductive biology and early life history, summarizing published data together with yet unpublished information.
Spawning and nursery areas
Although Illex argentinusspawnings have not been observed in nature up to the present, they could be confirmed by the presence of spawning and spent individuals which, in some cases, are found together with newly hatched paralarvae.
The spawning stocks differ in their area and season of spawning (Figure 1, Brunetti, 1988;
Hatanaka et al., 1985; Brunetti et al., 1998 a, b).
Fig. 1. I. argentinus. Spawning areas.
During summer (December-February) Summer Spawning Stock (SSS) spawns on the intermediate and outer shelf between 42°S and 46°S. Spent individuals dominate during February and sometimes they are caught dead. It was estimated that this group completes its spawning within a single and short period of about 30-60 days long.
During autumn (April-May) Southpatagonic Stock (SPS = autumn spawners) spawning takes place, but there is few information about its location. It would be situated along the Malvinas Current from 48°S to 45°S (Brunetti, 1988;
Brunetti and Ivanovic, 1992; Rodhouse et al., 1992). In July-August this stock have finished its spawning emigration and there has no cathes on the outer shelf and slope. Then the egg masses would be carried to the north up to Brazil-Malvinas Confluence by Brazil-Malvinas waters (Brunetti and Ivanovic, 1992). In winter (July-August) Bonaerensis-Northpatagonic Stock (BNPS = winter spawners) migrates towards oceanic waters where mating and spawnig take place. Fertilized or spent individuals are found on the slope between 36°S-37°30'S. It seems to be that the spawning grounds of this stock are close to the west side of Brazil-Malvinas Confluence.
28 Sesión 1: Estudios sobre reproducción y sobrevivencia de calamares y peces In spring (October-November) Spring
Spawning Stock (SpSS) spawns on the inner shelf between 38°S-39°S and inside San Matias Gulf.
Paralarva distribution
SSS paralarvae are distributed on the intermediate patagonic shelf, between 41°30'S-45°S, during December - March. The development of these paralarvae enhance the formation of a tidal frontal system between well-mixed coastal waters and shelf stratified waters, which starts during spring and continues until autumn (Glorioso, 1987). Paralarvae occur in the upper warm layer of the stratified side of the system.
The abundances increase from surface to 40 m, being maxima close the thermocline. Eggs in advanced embryonary stages were caught near the surface of the frontal zone with a phytoplankton net.
Autumn and winter spawning stocks (SPS and BNPS) share the same paralarval distributional area from March to August, in warm waters (outer shelf and Brazil waters) between 35°S-36°30'S, and on the intermediate bonaerensis shelf up to
39°30'S (Brunetti, 1988; Brunetti and Ivanovic, 1992). These paralarvae seem to drift southward judging by the presence of large amounts of juveniles during spring. A small
quantity of these paralarvae was found in the oceanic region off Argentina, inside the warm eddies resulting of Brazil-Malvinas Confluence, during August (Parfeniuk et al., 1992).
On the inner shelf, between 38°S and 40°S, paralarvae from SpSS are encountered during October and November.
Juvenile distribution
On the Bonaerensis-Northpatagonic shelf, juveniles between 1 and 10 cm ML (Figure 3), are found during September-November (Brunetti, 1988; Brunetti and Ivanovic, 1992). They belong to the SPS and BNPS. Those corresponding to SPS are migrating to the south up to reach 45°S-49°S, while those of the BNPS remain in the Bonaerensis-Northpatagonic shelf area. They are pelagic and usually complete their immigration into the breeding area and their recruitment to the bottom by the end of spring.
Fig. 2. I. argentinus. Paralarva distribution. Fig. 3. Illex argentinus. Juvenile distribution.
Juveniles between 1-5 cm ML and up to 2-3 month old, according to statolith readings, were found in the oceanic region off Argentina, most of them in mixed waters from the meanders and eddies resulting of Brazil-Malvinas Confluence and a less quantity in subantartic waters of the Malvinas Current, during August-September of 1988 (Parfeniuk et al., 1992). They have been probably carried towards the oceanic region from the hatchery ground by the eastward shift of the Brazil Current. Parfeniuk et al. (1992) reported exceptionally large catches of juveniles (3200-20000 individuals per hour) in the oceanic region during November 1989, which were significantly higher than those of 1988.
References
Brunetti, N.E. 1988. Contribución al conocimiento biológico pesquero del calamar argentino (Cephalopoda, Ommastrephidae, Illex argentinus). Tesis doctoral. Fac. Cs. Nat.
Museo, Universidad Nacional de La Plata: 135 p.
B r u n e t t i , N . E . & I v a n o v i c , M . L . 1 9 9 2 . Distribution and abundance of early life stages of squid (Illex argentinus)in the south west Atlantic. ICES J.mar.Sci., 49: 175-183.
Brunetti, N. E., M. L. Ivanovic & B. Elena.
1998a.Calamares omastréfidos (Cephalopoda, Ommastrephidae). En: Boschi, E. (Ed.). El Mar Argentino y sus recursos pesqueros.
Tomo II: Los moluscos de interés pesquero.
Cultivos y estrategias reproductivas de bivalvos y equinoideos: 37-68.
Brunetti, N., Ivanovic, M.Rossi, G.Elena, B. &
Pineda, S. 1998b. Fishery biology and life history of Illex argentinus. En: Okutani, T. (Ed.).
Contributed papers to the International Symposium on Large Pelagic Squids. Japan Marine Fishery Resources Research Center, Tokyo: 217-232.
Glorioso, P.D. 1987. Temperature distribution related to shelf-sea fronts on the Patagonic shelf. Cont. Shelf Res., 7(1): 27-34.
Hatanaka, H.S., Kawahara, S., Uozumi, Y. &
Kasahara, S. 1985. Comparison of life cycles of five ommastrephid squids fished by Japan:
Todarodes pacificus, Illex illecebrosus, Illex argentinus, Nototodarus sloani sloani and Nototodarus sloani gouldi.NAFO Sci. Coun.
Studies, 9: 59-68.
Parfeniuk, A.V., Froerman, Y. M. & Golub, A.N.
1992. Particularidades de la distribución de los juveniles del calamar (Illex argentinus) en el área de la depresión argentina. Frente Marítimo, 12(A): 105-112.
Rodhouse, P. G., Symon, C. & Hatfield, E. M. C.
1992. Early life cycle of cephalopods in relation to the major oceanographic features of the southwest Atlantic Ocean. Mar. Ecol. Prog.
Ser., 89: 183-195.