Aspects of the population ecology of the main target species of the gangmu fishery : palaemon xiphias (decapoda: palaemonidae)

Abstract

The gangmu fishery is an indigenous Maltese artisanal fishery in which a small beam trawl is used to capture shrimps and prawns associated with seagrass meadows. The gear used, known as il-gangmu, consists of two semi-circular metal bands welded together at right angles, to which is attached a 2.5m long net with a mesh size greater than 6 mm. As of the 31 May 2010, the fishery has been prohibited since it does not conform to EU regulations. However, Malta has requested a number of derogations in order to retain the use of the gangmu for cultural reasons. This traditional fishing activity is presently carried out at night between November and January by four licensed fishers and collectively lands an estimated 930 kg of shrimp annually. Although small scale, this fishery is operated on Posidonia meadows which are a 'priority habitat' in the EU's 'Habitat Directive'. A study by Zammit (2009) showed that the gangmu trawl has a relatively large impact on Posidonia beds and their associated biocoenoses. To date, no studies on the impacts by the fishery on the population of the main target species, Palaemon xiphias Risso, 1816, have been made. The present study concerns aspects of the population ecology of this species. Fishery-independent samples were collected seasonally between March 2009 and May 2010 from three different sites: Marsaxlokk Bay, Il-Hofra l-Kbira and St. Thomas Bay, using a typical gangmu operated by a professional fisher. Morphometric and reproductive parameters were measured for each individual shrimp collected.