Local hydrography and fishing drive life cycle strategies and population dynamics of the sea-bob shrimp Xiphopenaeus kroyeri in a coastal subtropical environment in Brazil

Abstract

The sea-bob shrimp is a shallow-water species whose population dynamics along the southern and southeastern coasts of Brazil is influenced by the upwelling of the South Atlantic Central Water (SACW). Since the SACW does not reach our study area, we hypothesize that life cycle and distribution patterns are dominated by the local regime of estuarine plumes. Also, we would expect higher biomasses and larger individuals in autumn due to the closed fishing season. We conducted a survey for a year, consisting of 20 monthly trawling hauls. Spawning peaks occurred in spring and autumn, related to rainy periods with greater estuarine loads of particulate material and phytoplankton production. The relative abundance of larger individuals increased with depth, while juveniles concentrated at shallower sites. Size classes prior to the closed season were affected by increased fishing during summer due to tourist demand. Water transparency and bottom temperature were the main factors controlling the distribution and life cycle of sea-bob shrimp. Seasonal changes in biomass could be related to the inshore–offshore migrations of the type-3 life cycle, compounded by the impacts of fishing. Thus, fishing and local hydrography can drive life cycle and distribution patterns of the species, with important management implications.