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

Abstract

Some biological parameters of Jenyns' sprat Ramnogaster arcuata in Bahía Blanca estuary, Argentina, were evaluated during a survey conducted on a monthly basis between September 2005 and August 2006. Jenyns' sprat specimens were observed in the estuary all through the year. Total length (TL; N = 721) ranged from 33 to 131 mm. No significant differences between the length–weight relationships of males and females were detected (P > 0.10). Positive allometric growth was observed in juveniles, males, females and sexes combined. Whole otolith analysis revealed four age groups (0–3), 1-year age being the most abundant. Gompertz growth parameters were L∞: 102.75 mm, k = 0.46 and t0 = 0.98 for males (r = 0.80), and L∞: 125.45 mm, k = 0.33 and t0 = 0.68 for females (r = 0.76). Males and females reached 50% sexual maturity (TL50) at 76 and 77 mm TL (age 1 year), respectively, and all individuals were sexually mature at a 110 mm-length at the age of 3 years. Macroscopic gonad inspection, gonadosomatic index and the high percentage of fish of the smallest size-class captured during spring and summer samplings indicate that the spawning season began in spring. Taken together, our results indicate that the biology of R. arcuata is fairly consistent with the biology of other temperate clupeoids.