Pelagic swarms and beach strandings of the squat lobster Munida gregaria (Anomura: Munididae) in the Beagle Channel, Tierra del Fuego

DIEZ, MARIANO J.; PEREZ-BARROS, PATRICIA; ROMERO, MC; SCIOSCIA, GABRIELA; TAPELLA, FEDERICO; CABREIRA, A.; MADIROLAS, A.; RAYA REY, A.; LOVRICH, GUSTAVO A.

POLAR BIOLOGY

SPRINGER

Año: 2012 vol. 35 p. 973 - 983

0722-4060

The present article is the first formal record of pelagic swarms and beach38 strandings of the squat lobster Munida gregaria in the Beagle Channel, southern South39 America. To describe size composition and natural diet of beach strandings and swarms,40 samples from strandings were taken in April 2007, March 2008 and March 2010.41 Samples from shoals were taken in May 2007 and April 2010. Also, during November42 2008 and January 2009, two acoustic surveys were carried out to describe both,43 horizontal distribution, and school metrics of swarms. Pelagic swarms and beach44 strandings were composed of 100% individuals of the morph gregaria of Munida45 gregaria. Mean size of males and females in both, beach strandings and swarms, were46 similar. The natural diet of pelagic Munida gregaria was composed mainly of47 crustaceans, unicellular algae and small macroalgae, sediment and particulate organic48 matter. Swarms of pelagic Munida took the shape of extended layers of varying density49 and height. Their positions in the water column were also variable: swarms were found50 at different parts of the water column, from the sub-surface to the near bottom layer.51 Occasionally, some large swarms occupied most of the water column. The absence of52 shoaling animals in the Beagle Channel between 1997 and 2002 and the recent53 occurrence of shoals are coincident with what occurs in other locations in Patagonia.54 We hypothesize that the factor influencing the formation of swarms must be acting at a55 regional scale.