Benthic community response to a passive fishing gear in a coastal lagoon (South Brazil)
2009
Netto, Sérgio A. | Pereira, Tiago J.
The influence of a passive shrimp fishing gear on benthic communities was studied at Laguna Estuarine System (South Brazil), a shallow choked coastal lagoon. The gear is composed by a group of fyke nets (25 mm mesh size) set in contact to the bottom, fixed with stakes forming a cage-like structure (around 30 m²). Samplings were conducted in the two main fishery areas of the estuarine system, Mirim (sand bottoms) and Imaruí (muddy bottoms) lagoon, in May 2005. In each area, 10 fyke net enclosures and 10 nearby sites without nets (control) were sampled. Microphytobenthos biomass (chlorophyll a and phaeopigments), number of taxa/species, density, Hill's number N ₁ and N ₂, and estimated number of species (ES₁₀₀) were used as community attributes. For the nematodes, values of the maturity index and abundance of Wieser's feeding type were used as well. The effects of the small-scale passive shrimp fishing gear on the coastal lagoon bottoms were dependent on the benthic component analyzed and the type of sediment. Whereas macrofauna was not affected by the net enclosures, meiofauna and nematodes, particularly from the mud sites were. At the sand site, the fyke net enclosures caused a decrease in the microphytobenthos biomass and changed the relative abundances of non-selective deposit feeding and epigrowth-feeding nematodes. The results indicated that small-scale static nets, such as the studied fyke enclosures, produced low intensity levels of disturbance. However, the enclosed area by nets at Laguna had already reached around 25,000 m². Given the large proportion of the coastal population involved and the area closed by nets, management policies should consider site-specific differences within the same estuarine system.
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