Temporal Changes in a Tropical Nekton Assemblage and Performance of a Prawn Selective Gear

The temporal variation of components of a moderately diverse (H=1.46) tropical estuarine fish assemblage (long. 146°30'E, lat. 8°45'S) was directed by salinities that had been determined by local oceanographic and probably topographic conditions. For this assemblage, two types of intrayear component profiles are predicted. Pooled data (1988-91) reveal a large component of regular/resident species (43%) in an assemblage which has been under a narrow temperature regime «5T). These results facilitate a discussion on the relevance and usefulness of three hypotheses often cited in studies concerning species diversity and component characteristics of the subtropical/tropical coastal nonreef fish assemblages. Manifestations of the assemblage are reflected in catch composition and weights of 39 trials conducted for a selective prawning gear whose performance in bycatch reduction, mainly for finfishes, is judged by an index, E, we have previously proposed. This gear is capable of harvesting the prawn while conserving the demersal fish. Behavioral responses to netting of the prawns and the finfishes, especially the nearshore surface schoolers such as leiognathids, are discussed from several points of view. An adaptation in terms of group selection for leiognathids of their locking mechanism of median fin spines has been interpreted. For the purpose of bycatch reduction or E enhancement, suggestions for improvements in net design and trawl configuration by considering the behavioral features of fish are made. Our original formula of E is modified for general use. Bycatch problems in the regional prawn fisheries and their possible impacts on fishery planning and development in Papua New Guinea as a developing country are discussed. The gear tested may offer enormous ecological and economic benefits. The gear is multipurpose, extremely simple, and can also be used as a biological sampler.

Temporal and Spatial Distribution of Catches of Tiger Sharks, Galeocerdo cuvier, in the Pelagic Longline Fishery Around the Hawaiian Islands

Thirty-five tiger sharks, Galeocerdo cuvier, have been reported caught in pelagic longline gearfrom 25 to 265 n.mi. off the Hawaiian Archipelago during December 1990-May 1993. Fifteen sharks were caught farther than 50 n.mi. offshore, indicating that tiger sharks do occur well offshore and removed from benthic topography. About 89% of the sharks were caught during October-March, while only 56% of the fishing effort occurred during that period.

Value chain analysis: shrimp, prawn and tilapia from the southern region of Bangladesh & feasibility analysis: brackish water sea-bass in the southern region in Bangladesh

The WorldFish Center is implementing the FtF Aquaculture Project in 20 southern districts in Bangladesh. The project is implemented under USAID’s Feed the Future initiative in collaboration with the Government of Bangladesh. The project contributes to achieving the ‘Feed the Future’ goals through four objectives: (i) dissemination of improved quality fish and shrimp seed, (ii) improving the nutrition and income status of farm households, (iii) increasing investment, employment and fish production through commercial aquaculture and (iv) policy and regulatory reform and institutional capacity building to support sustainable aquaculture growth. The project commissioned this study to gather insights into the value chains of shrimp, prawn and tilapia in the project region and the feasibility of promoting culture of brackish water sea-bass in the region. The findings and recommendations are expected to provide the foundation for the project to design its interventions for achieving its goals.

Genetic improvement of freshwater prawn, Macrobrachium rosenbergii (de Man) in India. Phase two: annual report for period January to December 2012

Macrobrachiurn rosenbergii is one of the widely cultured freshwater prawn species globally. India was the third largest producer of this species in 2007 and its aquaculture production rose to 43,000 metric tons (t) in 2005 froin less than 500 t in 1995. However, since then production has been declining and in 2008-09 it was 12,856 t, a reduction of more than 70% compared to 2005. There are several contributing factors to this decline, such as slow growth rate, poor survival, disease outbreaks, increase in cost of production, and availability of low risk alternative fish species. However, there is a consensus that poor seed quality leading to unsatisfactory growth and survival rates in ponds is one of the major reasons. Hence, the development of a systematic selective breeding program aimed at improving growth rate and ensuring high survival rate of this species was deemed a high priority. The Central Institute of Freshwater Aquaculture (CIFA), Bhubaneswar, India in collaboration with the WorldFish Center, Malaysia initiated a selective breeding program for this species in 2007.

Sustainability of elasmobranchs caught as bycatch in a tropical prawn (shrimp) trawl fishery

The bycatch of Australia’s northern prawn fishery (NPF) comprises 56 elasmobranch species (16 families). The impact of this fishery on the sustainability of these species has not been addressed. We obtained estimates of catch rates and the within-net survival of elasmobranchs. Carcharhinus tilstoni, C. dussumieri, Rhynchobatus djiddensis, and Himantura toshi represented 65% of the bycatch. For most species, >50% of individuals in the bycatch were immature, and some species recruited to the fishery at birth. For all species combined, 66% of individuals in the bycatch died in the trawl net. The relative sustainability of elasmobranchs caught as bycatch was examined by ranking species with respect to their susceptibility to capture and mortality due to prawn trawling and with respect to their capacity to recover once the population was depleted. The species that were least likely to be sustainable were four species of pristids, Dasyatis brevicaudata, and Himantura jenkinsii. These are bottom-associated batoids that feed on benthic organisms and are highly susceptible to capture in prawn trawls. The recovery capacity of these species was also low according to our criteria. Our results provide a valuable first step towards ensuring the sustainability of elasmobranchs that are caught as bycatch by highlighting species for management and research. The effectiveness of turtle excluder devices (TEDs) in reducing elasmobranch bycatch varied greatly among species but was generally not very effective because most of the captured species were small.

Acclimatization of juveniles of marine prawn Penaeus monodon to fresh water

Penaeus monodon, hitherto cultured in brackishwater, has been acclimatized to fresh water for culturing in fresh water system. One hundred juveniles of P. monodon measuring in an average 27.7 mm were procured from the coastal lowlying areas near Kakinada in Andhra Pradesh and were used to conduct an experiment on acclimatization. High percentage of survival (96.0%) was observed when the water salinity was lowered gradually at the rate of 10% per day for the first 2 days, 5% per day during the next 2 days and later at the rate of 1% per day.

Prawn culture and policy options: technology import and culture through fishermen vis a vis industry

Recent developments in aquaculture has created an awareness that prawn culture is a dollar spinner, in which industry can step in to earn foreign exchange by producing an expensive food iten which has a high market demand abroad. The Government has to take a policy decision whether the prawn culture should be done through small fishermen to improve their socio-economic condition or through private industry with the high technology input and predefined objectives of export trade. Perhaps a simultaneous operation of the two could be allowed best in the interest of India. Perhaps in the interest of quick development and adoption of high production technology, through fishermen organization, the development is encouraged through the implimentation of welfare and area development schemes. In some selected areas private industry may be encoureged to use high production technology to develop prawns.

Prawn seed resources and its farming potentialities in Sunkeri back waters (Kali Estuary - Karwar)

Prawn seed resources of Sunkeri back waters indicated the availability of Penaeus indicus, P. monodon, Metapenaeus dobsoni and M. monoceros. The monthly variation in seed composition, its correlation with environmental parameters and the aquaculture potentialities are reported

Karyotypic studies of freshwater prawn Machrobrachium rosenbergii

Chromosomal studies were conducted on Macrobrachium rosenbergii. On the basis of 50 metaphase plate counts, 38 metacentric, 14 sub metacentric and 66 telocentric chromosomes (2n = 118) were observed. The total length of the granomme was recorded to be 34.2 micron.

Importance of live feed organisms in prawn hatcheries: a review

Live food organisms play a vital role in the artificial propagation of penaeid prawn seeds. The methods practiced for the culture of phyto and zooplankton for rearing prawn larvae through their various developmental stages are reviewed. Selection of a suitable species depends mainly on the culture characteristics, local environmental factors and the food requirements of the species of prawns cultured. Suitability of a few species isolated from Karwar waters is discussed.

Mortality rates of the Poovalan prawn (Metapenaeus dobsoni) along the southwest coast of India with a note on the dynamics of its population

The annual instantaneous total mortality coefficient (Z) for the prawn Metapenaeus dobsoni has been estimated to range from 0.8 to 5.14 by the cumulative catch curve method. Different methods used in the study resulted in wide ranging values of natural mortality (M) (0.6 to 2.303), but the yield per recruit model when superimposed with the absolute yield values revealed the right order to be > 2. The biologically optimum yield of about 18 thousand tons is obtained for an effort of 2,702 trawlers per day for 215 fishing days when the annual exploitation ratio (E) is about 52%.

Faecal indicator organisms in frozen prawn products. Pt. 2. Survival of the organisms during freezing and frozen storage

The rate of survival of different types of faecal indicator organisms like Escherichia coli, enterococci etc. during freezing and frozen storage has been studied. Peeled and deveined prawns inoculated with a mixed culture of the above organisms were subjected to freezing and storage at -10̊F and examined for over four months.