Some biological parameters of Jenyns' sprat Ramnogaster arcuata (Pisces: Clupeidae) in south-western Atlantic waters

Abstract

Some biological parameters of Jenyns’ spratRamnogaster arcuatain Bahı ́a Blanca estuary, Argentina, were evaluated duringa survey conducted on a monthly basis between September 2005 and August 2006. Jenyns’ sprat specimens were observed inthe estuary all through the year. Total length (TL; N¼721) ranged from 33 to 131 mm. No significant differences between thelength–weight relationships of males and females were detected (P.0.10). Positive allometric growth was observed in juven-iles, males, females and sexes combined. Whole otolith analysis revealed four age groups (0–3), 1-year age being the mostabundant. Gompertz growth parameters were L1: 102.75 mm, k¼0.46 and t0¼0.98 for males (r¼0.80), and L1:125.45 mm, k¼0.33 and t0¼0.68 for females (r¼0.76). Males and females reached 50% sexual maturity (TL50)at76and 77 mm TL (age 1 year), respectively, and all individuals were sexually mature at a 110 mm-length at the age of 3years. Macroscopic gonad inspection, gonadosomatic index and the high percentage of fish of the smallest size-class capturedduring spring and summer samplings indicate that the spawning season began in spring. Taken together, our results indicatethat the biology ofR. arcuatais fairly consistent with the biology of other temperate clupeoids.