Least Squares Estimation Principle and its Geometrical Interpretation

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A prior for steepness in stock-recruitment relationships, based on an evolutionary persistence principle

Priors are existing information or beliefs that are needed in Bayesian analysis. Informative priors are important in obtaining the Bayesian posterior distributions for estimated parameters in stock assessment. In the case of the steepness parameter (h), the need for an informative prior is particularly important because it determines the stock-recruitment relationships in the model. However, specifications of the priors for the h parameter are often subjective. We used a simple population model to derive h priors based on life history considerations. The model was based on the evolutionary principle that persistence of any species, given its life history (i.e., natural mortality rate) and its exposure to recruitment variability, requires a minimum recruitment compensation that enables the species to rebound consistently from low critical abundances (Nc). Using the model, we derived the prior probability distributions of the h parameter for fish species that have a range of natural mortality, recruitment variabilities, and Nt values.

Length-based estimates of vital statistics in threadfin bream (Nemipterus japonicus) from Bay of Bengal, Bangladesh

ELEFAN 0, ELEFAN I and ELEFAN II were used to estimate vital statistics of Nemipterus japonicus from length-frequency data sampled along the coast of Bangladesh. The parameters L and K were estimated at 24.5 cm and 0.94 year super(-1). The values of M and F were found to be 1.81 and 1.58 year super(-1), respectively. The fish recruit to the fishery during May-June and September-October.

Vital statistics of marine fishes of Vanuatu

Vital statistics are presented for 38 marine species of Vanuatu based on previous studies conducted in the area, with parameters describing growth (6 species, 13 sets of parameters), mortality (estimates of M for 6 species), length-weight relationship (32 species), and reproduction (length at first maturity for 26 species, months of reproduction for 18 species). The species covered belong mainly to the family Lutjanidae.

Adopt sustainable development principle in aquaculture

The inadequate planning and inefficient management of coastal aquaculture has resulted into serious socioeconomic consequences. These are the displacement of rural communities which traditionally depended on mangroves due to large-scale mangrove conversion for shrimp and fish farming, land subsidence caused by excessive pumping of groundwater for use in aquaculture, financial losses due to disease outbreaks, and public health consequences due to red tide. In order to maximize the socioeconomic benefits of coastal aquaculture the adoption of the principles of sustainable development is recommended. Sustainable development is the management and conservation of natural resource base and the orientation of technological and institutional change in such a manner to ensure the attainment and continued satisfaction of human needs for present and future generations.

Invertebrate communities of Nabugabo Lakes: a vital support resource for the fisheries and ecosystem diversity

A field study of the invertebrate communities of the Nabugabo lakes(Nabugabo,Kayanja and Kayugi)showed the occurrence of copepoda, cladocera and rotifera(micro-invertebrates or zooplankton); Ephemeroptera and Diptera(macro-invertebrates or zoo-benthos). The most commonly encountered taxa were thermocyclops neglectus, moinamicrura,several rotiferan species(micro-invertebrates);P.adusta,chironomus, tanipodinae and trichoptera(macro- invertebrates). These organisms are assumed to be readily available as food sources for fishes in the Nabugabo lakes. Higher abundance and diversity of invertebrates occurred in Lake Nabugabo compared to Kayanja and Kayugi. There were no major differences in diversity and abundance of organisms between inshore and offshore areas of the different lakes. The highest diversity of macro-invertebrates(up to 15 taxa)was recovered from roots of macrophyte(higher water-based plants)such as Miscanthidium and Papyrus. The zooplankton of Nabugabo lakes typify a tropical assemblage with few species among genera and dominance of the communities by small-bodied organisms. Some taxa,common to many other water bodies such as Mesocyclops spp.,Calanoids(Copepoda), Caridina nilotica (Decapoda)were noticeably missing in the Nabugabo lakes community, probably due to environmental limitations including low conductivity and pH. Where they occur,these missing taxa have been shown to be key forage items for fishes and therefore their absence in Nabugabo lakes may have implications with respect to potential for fishery production. However other valuable invertebrate types such as cyclopoid copepods,ephemeroptera, chironomid and chaoborid larvae do occur in sufficiently high diversity and abundance to support viable fisheries resources. The high diversity and abundance of invertebrates associated with aquatic macrophytes such as Papyrus and Miscanthidium need to be protected through control of access and utilisation of shoreline vegetation.