A habitat-use model to determine essential fish habitat for juvenile brown shrimp (Farfantepenaeus aztecus) in Galveston Bay, Texas

A density prediction model for juvenile brown shrimp (Farfantepenaeus aztecus) was developed by using three bottom types, five salinity zones, and four seasons to quantify patterns of habitat use in Galveston Bay, Texas. Sixteen years of quantitative density data were used. Bottom types were vegetated marsh edge, submerged aquatic vegetation, and shallow nonvegetated bottom. Multiple regression was used to develop density estimates, and the resultant formula was then coupled with a geographical information system (GIS) to provide a spatial mosaic (map) of predicted habitat use. Results indicated that juvenile brown shrimp (<100 mm) selected vegetated habitats in salinities of 15−25 ppt and that seagrasses were selected over marsh edge where they co-occurred. Our results provide a spatially resolved estimate of high-density areas that will help designate essential fish habitat (EFH) in Galveston Bay. In addition, using this modeling technique, we were able to provide an estimate of the overall population of juvenile brown shrimp (<100 mm) in shallow water habitats within the bay of approximately 1.3 billion. Furthermore, the geographic range of the model was assessed by plotting observed (actual) versus expected (model) brown shrimp densities in three other Texas bays. Similar habitat-use patterns were observed in all three bays—each having a coefficient of determination >0.50. These results indicate that this model may have a broader geographic application and is a plausible approach in refining current EFH designations for all Gulf of Mexico estuaries with similar geomorphological and hydrological characteristics.

Taxonomic study of brown algae commonly growing on the coast of Karachi, Pakistan

Fourteen commonly occurring species of marine benthic algae, i.e., Colpomenia sinuosa (Mertens ex Roth) Derbes et Solier, Dictyopteris australis (Sonder) Askenasy, Dictyota dichotoma (Hudson) Lamouroux D. dumosa Børgesen, D. hauckiana Nizamuddin, D. indica Sonder, D. maxima Zanardini, Hincksia mitchelliae (Harvey) Silva, Jolyna laminarioides Guimardes in Guimarâes et al., Padina tetrastromatica Hauck, Sargassum tenerrinum J. Agardh, Spatoglossum variabille Figari et De Notaris, Stoechospermum marginatum (C. Agardh) Kültzing and Stokeyia indica Thivy et Doshi, belonging to all three classes of Phaeophyta, were collected from coastal areas near Karachi, Pakistan and their taxonomy determined. Although all are taxonomically known species, Dictyota dichotoma, D. dumosa, D. hauckiana, D. indica, D. maxima, Jolyna laminarioides, Padina tetrastromatica, Sargassum tenerritnum and Stokeyia indica are described for the first time from the coast of Pakistan.

Population dynamics and stock assessment of the spider prawn, Nematopalaemon tenuipes Henderson along the Maharashtra coast

Nematopalaemon tenuipes is an important component of non-penaeid prawn resources of the northwest coast of India. During 1979-82 period, it contributed 29.9% to the non-penaeid prawn and 5.6% to the total fish landings of Maharashtra. The von Bertalanffy growth parameter L∞, K and t(sub)0 were 77.38 mm, 1.31 and -0.02 year for the males while for the females these parameters were respectively 87.23 mm, 1.30 and -0.01 year. The natural mortality coefficient (M) was 3.54 and 3.52 and the average total mortality coefficient (Z) during the period was 9.09 and 7.79 for the males and females respectively. With the exploitation rates of 0.61 and 0.55 for the males and females during the period, the total stock of the species was 26,270 tonnes and the standing stock was 3,418 tonnes. The maximum sustainable yield (MSY) of the species under the prevailing fishing conditions was 15,744 tonnes which is close to the average yield of 14,726 tonnes from the nets. Hence further increase in effort is not suggested.