Trophic ecology of Mugil liza at the southern limit of its distribution (Buenos Aires, Argentina)

Abstract

In order to get to know the habitat and feeding habits of Mugil liza on the southern coast of Buenos Aires province, 65 specimens obtained at two sampling sites - the San Blas bay (SBB) and the mouth of the Quequén-Salado river (QSR) - during spring (November 2012) and summer (February 2013) were analyzed. Specimens were measured, sexed and weighed, their stomachs were removed and their stomach contents weighed and analyzed under the stereoscopic microscope. The specimens were adults, 28-49 cm in length and weighing 380-1100 g. Population growth was higher in the SBB (TW: 0.003*TL3.36), than in RQS (TW: 0.045*TL2.61). About 98% of the stomachs had some content, their repletion rate being of between 0.4 and 1.2%. About 75% of the stomachs contained very fine sand with few benthic organisms (algae, copepods, foraminifera), whereas the remaining 25% of stomachs contained coarse sand and a greater presence of benthic fauna (amphipods, bivalves, gastropods and coral organisms). The linear relationship between the weight of stomach contents and the total weight and length of the fish showed that the rates of growth (slope) were the same at both sites, but intercept values were significantly higher for San Blas bay (test parallelism; p < 0.001).