The length-weight relationships (LWRs) of Macrobrachium lamarrei (H. Milne-Edwards, 1837) was studied to construct the generalized relationships of body weight to carapace length measurements for male, female and combined prawn population separately over a calendar year. A total of 1018 specimens were used for this study. The parameter values of the equation W = a L b describing the relationships between body weight and carapace length for male, female and combined prawns. The parameter of equations, a varied from 0.00096 to 0.00333, 0.00059 to 0.00728 and 0.00081 to 0.00440 for male, female and combined prawn population respectively. On the other hand, the slope of equations, b varied from 2.4363 to 2.8229, 2.0761 to 3.0314 and 2.2915 to 2.8998 for male, female and combined prawn population respectively indicating isometric growth in females but negative allometric for males suggesting that female prawns were comparatively in better condition than males of the same population. The generalized length-weight relationship was fitted with the pooled data of all monthly samples for male, female and combined prawn separately which were BW = 0.0008 CL 2.924 , BW = 0.0012 CL 2.783 and BW = 0.0010CL 2.845 respectively indicating negative allometric growth as b varied from 2.783 to 2.924. The results further revealed that all length-weight relationships (LWRs) were highly correlated (r 2 > 0.904).

Viruses that infect fish are understudied, yet they provide important evolutionary context to the viruses that infect terrestrial vertebrates. We surveyed gill tissue meta-transcriptomes collected from two species of native freshwater fish from Aotearoa New Zealand—Retropinna retropinna and Gobiomorphus cotidianus. A total of 64 fish were used for gill tissue meta-transcriptomic sequencing, from populations with contrasting life histories—landlocked (i.e., lacustrine) and diadromous—on the South Island and Chatham Islands. We observed that both viral richness and taxonomic diversity were significantly associated with life history and host species, with lacustrine R. retropinna characterised by higher viral alpha diversity than diadromous R. retropinna. Additionally, we observed transcripts of fish viruses from 12 vertebrate host-associated virus families, and phylogenetically placed eight novel RNA viruses and three novel DNA viruses in the Astroviridae, Paramyxoviridae, Orthomyxoviridae, Rhabdoviridae, Totiviridae, Poxviridae, Alloherpesviridae, and Adintoviridae in their evolutionary contexts. These results represent an important survey of the viruses that infect two widespread native fish species in New Zealand, and provide insight useful for future fish virus surveys.

Shrimp has become one of the most important export products in recent decades due toincreasing international demand. Shrimp farming is performing significant role in thelivelihoods of rural people of southwestern part of Bangladesh which is considered thecore areas for shrimp farming. To continue the trend of exporting shrimp worldwide it isvery much needed to be familiar with the current culture practices with the precautionstaken by the shrimp farmers. A total of 30 shrimp farmers in Shyamnagarupazilla ofSatkhira district were interviewed to understand the present status of shrimp farming alongwith to identify the problems faced by the farmers, and to formulate somerecommendations for better shrimp production development. Study showed thatpolyculture was the only culture technique followed by the shrimp farmers using naturalwater sources like rain and tide. Bagda (Penaeusmondon) was the dominant culturedspecies followed by Harina (Metapenaeusmonoceros) because of their economicsignificance. Although wild post-larvae (PL) are better in quality than hatchery producedPL, farmers collected PL from both sources. Farmers usually used inorganic fertilizers likeUrea and TSP instead of organic one, but they preferred natural feeds for cost efficiencyand management purposes. The study also identified that shrimp diseases (white spot, gillrot and fin rot), lower market price, flood, high mortality and lack of scientific knowledgewere the major constraints in shrimp farming. Government, donor agencies, planners,researchers and NGOs, therefore, should come forward to assist farmers for mitigatingproblems and achieve sustainable shrimp export earnings of Bangladesh. Res. Agric., Livest. Fish.7(2): 311-320,  August 2020

Community Based Fisheries Management (CBFM) approach appears to be an important factor in managing fisheries successfully. Thus, this study aims to investigate and evaluate the fisheries management practices and its impact on the livelihood of the fisheries community of Sherudanga beel in Rangpur district (Bangladesh) for a period of 12 months, from March 2010 to February 2011. The study was conducted based on Community Based Fisheries Management (CBFM) practices, beel biodiversity, fish production, socioeconomic and livelihood condition of the fishermen community. The studied beel is 83 acre seasonal floodplain, which was mainly used by a community consisting of 80 families for their livelihood, where the CBFM approach was introduced by the community. At pre-CBFM, there was no controlled management system from any NGO or even Government for the proper management of the beel. Recently, community fishers leased out this beel from the government in year 2000 for 12 years and started to manage it. The CBFM project works for the development of fishery system, the fishermen community and the general society. The yearly gross fish production was higher than pre-CBFM period, implying that average abundance and fish biodiversity were significantly higher in the CBFM implemented beel. Majority of the fishermen had primary level education (37.5%) compared to 27.5% and 16.5% having secondary level and above secondary level education respectively, while 18.75% of them could sign their name only, indicating the improvement of education level among fishers. About 43.75% of them had small size family, while 40.0% and 16.25% had middle and large size families respectively. The prevalence of unconstructed house was the highest (77.5%) while few of them (22.5%) had semi constructed house. About 68.75% of the fishermen had medium income, while 12.5% and 18.75% had small and large income respectively. More than half (56.25%) of the fishermen received credits from different sources while rest (43.75%) of them did not get any credits. In conclusion, the overall findings showed that community based fisheries management has significantly increased annual fish production, lifted household income levels, improved access to credit from a wide range of sources and enabled livelihood diversification.

Landlocking of diadromous fish in freshwater systems can have significant genomic consequences. For instance, the loss of the migratory life stage can dramatically reduce gene flow across populations, leading to increased genetic structuring, and stronger effects of local adaptation. These genomic consequences have been well-studied in some mainland systems, but the evolutionary impacts of landlocking in island ecosystems are largely unknown. In this study, we used a genotyping-by-sequencing (GBS) approach to examine the evolutionary history of landlocking in common smelt (Retropinna retropinna) on Chatham Island, a small isolated oceanic island 650 km southeast of mainland New Zealand. We examined the relationship among the Chatham Island and mainland smelt, and used coalescent analyses to test the number and timing of landlocking events on Chatham Island. Our genomic analysis, based on 21,135 SNPs across 169 individuals, revealed that the Chatham Island smelt were genomically distinct from the mainland New Zealand fish, consistent with a single ancestral colonisation event of Chatham Island in the Pleistocene. Significant genetic structure was also evident within the Chatham Island smelt, with a diadromous Chatham Island smelt group, along with three geographically structured landlocked groups. Coalescent demographic analysis supported three independent landlocking events, with this loss of diadromy significantly pre-dating human colonisation. Our results illustrate how landlocking of diadromous fish can occur repeatedly across a narrow spatial scale, and highlight a unique system to study the genomic basis of repeated adaptation.