Seasonal dynamics in abundance and size structure of Micropogonias furnieri in a temperate hyper-saline estuary.

BLASINA G.E.; MOLINA J.M.; DÍAZ DE ASTARLOA J.M.; LOPEZ CAZORLA A.C.

Mar del Plata

Congreso; XVIII Congreso Latinoamericano de Ciencias del Mar-COLACMAR; 2019

Understanding the responses of fish to environmental fluctuations is critical to support effective management and conservation of fishery resources. Seasonal dynamics of abundance (estimated as CPUE) and size structure of Micropogonias furnieri were analyzed from samples obtained from six sampling sites in Bahía Blanca estuary (BBE). Specimens were obtained monthly using the fishing technique of channel closures with nets (commonly used in the study area by local fishermen) and two shrimp nets. Sampling effort at each net was standardized considering one tide as the time unit. CPUE values increased with the increase in salinity for all length classes; however, the influence temperature varied according the fish total length (TL) (Figure). The monthly distribution of M. furnieri sizes showed that the highest TL values were registered from December to March and that the smallest individuals occupy BBEmainly during autumn and winter seasons, which it corresponds with the seasonalchanges in temperature. Adult stage ingress towards the inner area of BBE explains the increase in mean TL of individuals captured at the end of spring until early autumn. This pattern could be associated to a post-spawning feeding movement from the reproductive area in the outer zone of BBE. The size structure of M. furnieri found in BBE could be indicative of seasonal changes related to large scale migration linked to changes in water temperature, and to small scale trophic migrations from the spawning areas. The presence of juvenile individuals supports the hypothesis of BBE being a nursery area. Different dynamics have been described in the Río de la Plata estuary, where this species shows a spatial segregation for stages, mainly influenced by bottom salinity and the spawning takes place in its inner area (Jaureguizar et al., 2016).