ABSTRACT

Identifying populations and establishing the connectivity between neighbouring stocks are central issues for the assessment and management of coastal marine fish species. In this paper, we analysed the population structure of the demersal sciaenid argentine croaker Umbrina canosai, endemic in the warm, temperate southwestern Atantic between southeastern Brazil (SE) and Argentina, by combining two phenotypic techniques: otolith shape analysis and fish growth rate. Three otolith morphotypes were consistently identified, one in the northern latitudinal range in SE, and two in the southern range of the species from southern Brazil to Argentina. Two stocks with differences in growth rate were identified, one with a significantly smaller asymptotic length in the northern range (L_∞= 340.08; k = 0.267; t₀ = −2.177) and the second in the southern range (L_∞= 425.08; k = 0.236; t₀ = −2.46), where no growth differences were observed between fishes with the two otolith morphotypes. Although genetically U. canosai can be considered to form a single panmictic population, growth and otolith shape indicate that there are two different stocks, one in southeastern Brazil and another in the southern distribution, confirming previous parasitological studies. The difference in otolith morphotypes in the southern range suggests that two subpopulations share the same reproductive grounds, although probably feed in different locations.

摘要

确定种群和建立相邻种群之间的联系是沿海海洋鱼类物种评估和管理的核心问题。在本文中，我们通过结合两种表型技术：耳石形状分析和鱼类生长率，分析了巴西东南部 (SE) 和阿根廷之间温暖、温带西南大西洋地区特有的底层 sciaenid 阿根廷黄鱼Umbrina canosai的种群结构。一致地确定了三种耳石形态类型，一种在东南部的北部纬度范围内，另两种在从巴西南部到阿根廷的物种南部范围内。确定了两种增长率不同的股票，一种在北部范围内的渐近长度明显更小 ( L _∞= 340.08; k  = 0.267；t ₀  = -2.177) 和南部范围内的第二个 ( L _∞ = 425.08; k  = 0.236; t ₀  = -2.46)，其中在具有两种耳石形态类型的鱼类之间没有观察到生长差异。尽管在遗传上可以认为U. canosai形成一个单一的 panmictic 种群，但生长和耳石形状表明有两种不同的种群，一种在巴西东南部，另一种在南部分布，这证实了以前的寄生虫学研究。南部地区耳石形态类型的差异表明，尽管可能在不同的地点觅食，但两个亚群共享相同的繁殖地。