INIDEP Informe Técnico Nº 27 – 1999

INIDEP Informe Técnico Nº 27 – 1999

Hansen, J.E. 1999. Estimación de parámetros poblacionales del efectivo de sardina fueguina (Sprattus fuegensis) de la costa continental argentina.
INIDEP Informe Técnico, 27: 18 p.
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Patagonian sprat is probably the only pelagic fish species having a considerable biomass within the Argentine Seasouth of 45ºS. There are two populations, the first inhabiting mainly the coastal region around Malvinas Islands and the other close to the coast off Santa Cruz and Tierra del Fuego Provinces, including the fuegian channels. Some results of two seasonal (autumn and spring) patagonian sprat assessment surveys carried out during 1996 are shown. The autumn cruise covered the area between 50° and 55°S, from the continental coast up to 60 m depth, whereas the spring survey extended up to 90 m depth including Le Maire Strait and part of the Beagle Channel. During both seasons, in waters ranging 6.2 – 8.8°C temperature, the species distributed very close to the coast. Sprat samples analyzed comprised 36 – 168 mm total length individuals with a clear predominance of those measuring 100 mm or less. Mean size tended to increase southwards. Larger sprats were present in the most southern fishing trawls and within the Beagle Channel. Said individuals did not reach the maximum sizes found around Malvinas Islands. Von Bertalanffy growth function describing the total length (mm) increase of the Argentine continental coast sprat was fitted as follows: Lt = 140 {1 – exp [- 1.015 ( t – 0.14)]}. Seasonal Total Length (mm)- Weight (g) relationships were also fitted: Autumn: P = 2.01 * 10-6 * L3.2404; Spring: P= 0.80 * 10-7 * L3.9497. The size-at-50% first maturity was estimated to be 119.94 mm total length what means an age at 50% maturity (t50%) of about 2.05 years. The population mortality rate as calculated from estimated numbers-at-age indicate that population mortality rate would range between 1.40 and 1.51. The indirect methods used to estimate mortality rates gave very different values (between 0.59 – 0.92) thus casting great uncertainty on the subject.