Spatial distribution of southern brown shrimp (Farfantepenaeus subtilis) on the Amazon continental shelf: a fishery, marine geology and GIS integrated approach

The spatial distribution of the southern brown shrimp Farfantepenaeus subtilis (Pérez-Farfante, 1967) was studied based on industrial fishing fleet activities and is associated with geological and oceanographic characteristics of the benthonic environments on the Amazon continental shelf. Using a geographical information system (GIS) this paper sought to calculate the relative abundance of brown shrimp based on catch per unit effort (CPUE) and compare it with bathymetry, type of sedimentary structure, sedimentation rate and bottom salinity. As a result, we have concluded that the relative abundance (in terms of CPUE) is not uniformly distributed in space. Spatial analysis indicates that commercial trawling efforts were made in the (foreset) region of the subaqueous Amazon delta at depths of 40 to 60 m. In this region, prawn are responsible for the bioturbation of the sediments and the creation of a sedimentary structure called mottled mud. In the foreset region, sedimentation rates progressively increased up to 10 cm.yr-1; re-suspension was reduced and bottom salinity was high (~ 36). It appears that all of these factors define a stable muddy area with intense bioturbation. This notable biological activity is to be explained by the occurrence of a high F. subtilis abundance that appears to originate in a microbial loop. We concluded that by combining fishery information with environmental data from a GIS, it was possible to identify abundance distribution patterns for southern brown shrimp and other economically important fishery resources and to understand how they change on a large spatial-scale.

Deep-sea sponge grounds enhance diversity and abundance of epibenthic megafauna in the Northwest Atlantic

Beazley, L. I., Kenchington E. L., Murillo, F. J., and Sacau, M. 2013. Deep-sea sponge grounds enhance diversity and abundance of epibenthic megafauna in the Northwest Atlantic. – ICES Journal of Marine Science, 70: . The influence of structure-forming deep-water sponge grounds on the composition, diversity, and abundance of the local epibenthic megafaunal community of the Flemish Pass area, Northwest Atlantic was statistically assessed. These habitats are considered vulnerable marine ecosystems and, therefore, warrant conservation measures to protect them from bottom fishing activities. The epibenthic megafauna were quantified from four photographic transects, three of which were located on the western slope of the Flemish Cap with an overall depth range of 444–940 m, and the fourth in the southern Flemish Pass between 1328 and 1411 m. We observed a diverse megafaunal community dominated by large numbers of ophiuroids and sponges. On the slope of the Flemish Cap, sponge grounds were dominated by axinellid and polymastid sponges, while the deeper sponge ground in the southern Flemish Pass was formed mainly by geodiids and Asconema sp. The presence of structure-forming sponges was associated with a higher biodiversity and abundance of associated megafauna compared with non-sponge habitat. The composition of megafauna significantly differed between sponge grounds and non-sponge grounds and also between different sponge morphologies. Surface chlorophyll a and near-bottom salinity were important environmental determinants in generalized linear models of megafaunal species richness and abundance.

Distribution of Micropogonias furnieri at different maturity stages along an estuarine gradient and in relation to environmental factors

Whitemouth croaker (Micropogonias furnieri) maturity stages distribution and its relation to environmental factors was evaluated from 166 stations sampled within the Río de la Plata estuary (36°S–56°W) during spring 1994–1999 and 2003. A canonical correspondence analysis was used to explain whitemouth croaker distribution and estimate its relation to environmental factors (depth, surface and bottom waters temperature and salinity, bottom salinity and temperature horizontal gradients and vertical stratification). Results indicate that bottom salinity horizontal gradient (BSHG) and depth have a major influence on M. furnieri maturity stages spatial distribution; bottom salinity and temperature play a significant although secondary role. Spent and resting adult stages were associated to low BSHG, high salinity and low temperature while immature, gravid (with hydrated oocytes) and running stages to low salinity and high temperature. Although immature, gravid and running stages were clearly linked to similar bottom salinity they were segregated, with gravid and running stages associated to a strong BSHG. The distinct preferences of the different spawning stages result in a segregated distribution pattern along the main axis of the Río de la Plata estuary. The area with low salinity and high horizontal bottom salinity gradient (habitat for gravid and running stages) was located at the river head. The horizontal retention mechanism associated to BSHG within the spawning habitat favours growth and survival of fish larvae and the subsequent transport to nursery habitats.