Microsatellite variation and significant population genetic structure of Mugil liza in South America coastal waters.

MAI, A.C.G.; MARINS, L.F.;CASTELLO, J.P.; LEMOS, V. M.; MONTEIRO-NETO, C.; MIRANDA, L.; SCHWINGEL, P. R.; GONZÁLEZ CASTRO, M. ; VIEIRA, J. P.

Congreso; The Changing Coastal and Estuarine Environment: A Comparative Approach; 2012

Mugil liza distributes in the Western Atlantic from Argentina (AR) to Venezuela. This species has a high commercial and social value in the small-scale and the purse-seine fisheries in Brazil. In autumn, triggered by a drop in water temperature, large shoals start the reproductive migration leaving estuaries and coastal lagoons from AR and Uruguay, joining large migrating shoals of Rio Grande do Sul (RS), Santa Catarina (SC), and other southern Brazilian states. More than 90% of total catches are made in SC and RS, during this migration, when the fishery targets dense shoals, making it especially vulnerable. So far, there is no fishery management, but identifying its populations is urgent. We investigated the genetic populations using four polymorphic microsatellite regions, synthesized from M. cephalus. We sampled 50 adult individuals from each of the following locations: Rio de Janeiro (RJ), São Paulo (SP), SC, RS and AR. The lengths of the DNA fragments were read on a polyacrylamide gel, 6%, with markers 10 and 50 bp, and stained with silver nitrate. Using the Arlequin, our results indicated significant genetic divergence (Fst) between Rio de Janeiro and other places compared (RJxSP=0.0145; RJxSC=0.0106; RJxRS=0.0115; RJxAR=0.0210; all with p≤0.01). The samples from SP to AR showed low genetic divergence (SPxSC=-0.0009; SPxRS=-0.0026; SPxAR=0.0041; SCxRS=-0.0019; SCxAR=0.0017; RSxAR=-0.0044, all p>0.05). Based on these results, we concluded that there are at least two populations. One is distributed from AR to SP, Brazil, subjected to a strong fishing pressure during the reproductive migration, suggesting an urgent need for a fisheries management plan. The second population occurs from RJ to the north, but there is little information available on its range distribution and fisheries. Further investigations should be carried out to establish the northern limit of this population or to elucidate the existence of other populations.