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Spatial and temporal patterns in size and maturation of Loligo plei and Loligo sanpaulensis (Cephalopoda: Loliginidae) in southeastern Brazilian waters, between 23°S and 27°S
Amanda R. Rodrigues and Maria A. Gasalla

Patterns of population dynamics of Loligo plei and Loligo sanpaulensis in southeastern Brazil were investigated with samples obtained from commercial catches and research cruises from 1999 to 2000 and from 2002 to 2003. Size and maturity structure of the two species varied according to depth and season. Body size decreased with depth for L. plei, whereas for L. sanpaulensis size increased with depth up to 100 m and decreased again in deeper areas. GSI and incidence of mature animals decreased with depth in both species. L. plei females matured at a larger size in summer, while size at maturity in L. sanpaulensis was greater in autumn. For L. plei, reproductive events occurred in the late winter and spring, in depths up to 40 m, and during summer in inshore waters. L. sanpaulensis increased reproductive activity in summer, winter and spring between depths of 30 and 80 m. The presence of high proportions of immature squid offshore suggests that juveniles might develop in these areas and, upon maturation, migrate back to inshore waters to spawn, particularly in spring and summer. However, differences found in aggregation patterns in different depth strata, as well as the seasonal differences found in the size structure of L. plei and L. sanpaulensis, could ultimately be due to changes in the water column related to food availability. Considering that L. plei and L. sanpaulensis are both caught as by-catch by shrimp trawlers throughout the year, we also discuss hypotheses on the life cycle of the species and its implications for fishery management. We recommend measures to protect squid spawning grounds by creating spring and summer protected areas where trawling would be prohibited until 60 m depth, i.e. in the area and time of year when mature individuals concentrate.

Keywords: Loligo, squid, cephalopod, spatial and temporal patterns, fisheries, Brazil
Contents of this volume Sci. Mar. 72(4) : 631-643 Back PDF
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