Preeliminary results on the biology of Symphurus jenynsi in Bahia Blanca estuary.

The Cynoglossidae family comprises benthic fishes associated with coastal environments and frequently linked to fishing activity (Munroe, 1998). Symphurus jenynsi, a species regularly caught as bycatch in artisanal fisheries, inhabits the waters of Buenos Aires Province (Molina et al., 2021). In Argentina, information on S. jenynsi is very limited and is mainly restricted to taxonomic aspects and general observations on its distribution and ecology. The overall objective was to perform a biological characterization of the S. jenynsi population in in Bahia Blanca estuary. The fish were obtained from scientific fishing surveys operations using bottom trawling nets. The species' morphometric parameters, diet, and reproductive aspects were quantified. A total of 65 specimens were analyzed, with total lengths ranging from 7.3 to 19.4 cm and total weights from 2.15 to 59.57 g. The overall length-weight relationship showed positive allometric growth. When analysed by sex, females (N = 39) exhibited a steeper allometric slope (b = 3.37; R² = 0.970) compared to males (b = 3.10; R² = 0.994; N = 11). The average Gonadosomatic Index (GSI) for females was 0.31 and for males 0.84. The average Hepatosomatic Index (HSI) was estimated at 0.28 for females and 0.55 for males. Stomach contents were present in 100% of the analysed individuals. Polychaetes were the main and dominant component of the diet, with a PIRIP of 98.37% (%FO = 96.55, %N = 67.19, %W = 95.76). The remaining prey assemblage consisted of other crustaceans (PIRIP = 0.37%), amphipods (0.27%), algae (0.27%), copepods (0.20%), and crabs (0.15%). The species exhibits a marked specialist feeding strategy, placing polychaetes in the quadrant of high frequency of occurrence and high specific abundance of the prey.