Benthic community response to a passive fishing gear in a coastal lagoon (South Brazil)

Abstract

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 m 2 ). 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 (ES 100 ) 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 m 2 . 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.

Geochemical markers as a tool to assess sedimentary organic matter sources of the Laguna Estuarine System, south Brazil: aliphatic and polycyclic aromatic hydrocarbons

“…Since the few studies carried out at this site are focused on ecological and biological aspects, 13,[15][16][17][18] this study aims to assess the AH and PAH sources and concentrations, to serve as a baseline for future monitoring programs and to improve the environmental sustainability. To achieve this goal, the separation, identification and quantification of n-alkanes, isoprenoid hydrocarbons, pentacyclic triterpanes and PAH were carried out.…”

Effect of sediment on meiofauna and Nematoda structure in different freshwater Amazon environments under the influence of mesotides

“…In fact, sandy beaches with coarse sediment grains tend to have high densities of predatory Nematoda (Moens et al ., 2014). On the other hand, Xyalidae, family of the most abundant genus in muddy environments ( Zygonemella ), is frequently associated with estuarine environments with clayish or silty sediment, where this group occurs in high densities (Meurer and Netto, 2007; Netto and Pereira, 2009; Costa and Netto, 2014). Despite this clear preference, both Oncholaimellus and Theristus , as well as Daptonema (also belonging to Xyalidae), were the genera shared by all environments.…”

Trace Metal Levels in Muscles and Exoskeleton of Pink Shrimp (Penaeus brasiliensis and paulensis) from a Subtropical Coastal Region, Laguna Estuarine System, Brazil

“…Laguna Estuarine System, a choked coastal lagoon in southern Brazil was selected for this study. The lagoon has an area of 184 km 2 , a mean depth of 2 m, and it is isolated from the ocean by a sand barrier to the east, as shown in Figure 1 (Netto and Pereira, 2009). Small rivers to the west contribute freshwater input and sediment delivery.…”

“…Each group of nets forms a cage like structure. In the center of the enclosure, a fluorescent lamp produced by a car battery is placed on a stake, as shown in Figure 3 (Netto and Pereira, 2009). The positively phototropic shrimp are attracted to the light and enter the net.…”