906 resultados para Artificial satellites in geographical research
Resumo:
Despite extensive study, it still is not clear whether artificial reefs produce new fish biomass or whether they only attract various species and make them more vulnerable to fishing mortality. To further evaluate this question, the size and age of red snapper (Lutjanus campechanus) were sampled from April to November 2010 at artificial reefs south of Mobile Bay off the coast of Alabama and compared with the age of the artificial reef at the site of capture. Red snapper were collected with hook and line and a fish trap and visually counted during scuba-diver surveys. In the laboratory, all captured red snapper were weighed and measured, and the otoliths were removed for aging. The mean age of red snapper differed significantly across reefs of different ages, with older reefs having older fish. The mean age of red snapper at a particular reef was not related to reef depth or distance to other reefs. The positive correlation between the mean age of red snapper and the age of the reef where they were found supports the contention that artificial reefs in the northern Gulf of Mexico enhance production of red snapper. The presence of fish older than the reef indicates that red snapper are also attracted to artificial reefs.
Resumo:
Artificial Insemination (AI) is a tool for genetic manipulation in the shrimp stocks. It is seen as one of the means for propagating shrimp culture to new areas by controlled reproduction. Attempts at artificial insemination in the dominant closed-thelycum penaeid shrimps species of the area viz. Metapenaeus affinis and Metapenaeus brevicornis were induced in wild adult stocks collected off Mumbai coast. Female specimens were subjected to unilateral eyestalk ablation by pinching so as to induce moulting and maturation. AI was performed two days after moulting on these females when the cuticle was still soft and flexible. Moulting also ensured rejection of initial spermatophores, if present. Response of males to electrical stimulation for spermatophore expulsion was spontaneous. Use of tissue glue for spermatophore retention was found to be unnecessary. Latency period ranged between10-16 days, while spawning occurred within 10-12 days of spermatophore transfer. Three partial spawning were recorded viz., two in Metapenaeus affinis and one in Metapenaeus brevicornis with an average spawning and hatching rates of 30% and 72.3% respectively. Average survival from first nauplius (N1) to one-day old post-larva (PLI) was a meager 3.43%. Use of AI in genetic manipulation of shrimp stocks for aquacultural purposes is indicated.
Resumo:
Some basic concepts of fishery economics and management, and fish population dynamics are recalled, as presented during a course held at the Instituto de Investigaçāo Pesqueira from 23 February to 15 March 1988 in Maputo, Mozambique. Also, some basic elements of length-based stock assessment are reviewed, with emphasis on their implementation through the “Compleat Elefan" package, used extensively during this course, when the participants analyzed their data and wrote first draft of manuscripts incorporating the results of these analyses. Some problems relative to sampling and to seasonal growth oscillations are discussed with special reference to conditions in Mozambique.
Resumo:
This working paper is part of a review of aquaculture technologies and gender in Bangladesh in the period 1990 to 2014. It assesses how gender has been integrated within past aquaculture technology interventions, before exploring the gender dimensions associated with current approaches to transferring knowledge about homestead aquaculture technology. It draws out existing knowledge, identifies research gaps, and selects practices to build upon--as well as practices to move away from. The review examines the research and practice of WorldFish and other development partners in Bangladesh through consultations, a review of gray and published literature, and fieldwork. It aims to contribute to the development of aquaculture technology dissemination methodologies that strengthen and underpin women’s participation in aquaculture.