Integration of submersible transect data and high-resolution multibeam sonar imagery for a habitat-based groundfish assessment of Heceta Bank, Oregon

In the face of dramatic declines in groundfish populations and a lack of sufficient stock assessment information, a need has arisen for new methods of assessing groundfish populations. We describe the integration of seafloor transect data gathered by a manned submersible with high-resolution sonar imagery to produce a habitat-based stock assessment system for groundfish. The data sets used in this study were collected from Heceta Bank, Oregon, and were derived from 42 submersible dives (1988–90) and a multibeam sonar survey (1998). The submersible habitat survey investigated seafloor topography and groundfish abundance along 30-minute transects over six predetermined stations and found a statistical relationship between habitat variability and groundfish distribution and abundance. These transects were analyzed in a geographic information system (GIS) by using dynamic segmentation to display changes in habitat along the transects. We used the submersible data to extrapolate fish abundance within uniform habitat patches over broad areas of the bank by means of a habitat classification based on the sonar imagery. After applying a navigation correction to the submersible-based habitat segments, a good correlation with major boundaries on the backscatter and topographic boundaries on the imagery were apparent. Extrapolation of the extent of uniform habitats was made in the vicinity of the dive stations and a preliminary stock assessment of several species of demersal fish was calculated. Such a habitat-based approach will allow researchers to characterize marine communities over large areas of the seafloor.

The four seam trawl nets operated off Cochin: an analysis of the design aspects: the integration of the various parts of trawl

A study has been made of 22 different designs of four seam trawls operated at Cochin for shrimp trawling. Formulae for the relations between the different parts of the nets have been derived.

Prospects of integration of aquaculture with animal husbandry and land crop culture in Tripura State

Tripura is a densely populated small state with meagre water resources. 47.51% of the population is constituted by socio-economically backward, illiterate, orthodox, tribal and scheduled castes. Some of them are nomad and a majority of the rest of the population is refugees from Bangladesh, but almost 100% is fish eater. Settlement of tribes in villages, provision of nutritious food and employment therefore calls for proper utilization of every resource they have. The State is poor in water resources but recently has created 21,636.23 ha of new water area. Tripura is rich in pig population, besides poultry birds. Paddy is the main crop cultivated in arable lands. An integration of livestock raising and land based agriculture with pisciculture practices around mini barrages will help in solving the problems to a great extent. The paper is an attempt to outline the prospects of integration of aquaculture with animal husbandry and land based crop culture in Tripura State.

Gender integration in aquaculture research and technology adoption processes: lessons learned in Bangladesh

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.

Fish-makhana (Euryale salisb) integration: a case study of sustainable aquafarming system in north Bihar

The paper deals with a technique to synchronize two crops, fish and makhana (Euryale ferox Salisb) in a pond. In such eco-friendly integration both crops are mutually benefited. Decomposed plant parts of makhana crop form organic matter that releases nutrients in the water to enhance plankton population. Organic detritus not only acts as food for bottom dwelling fishes (mrigal and common carp) but also provides a suitable substratum for the growth of zooplankton, insect larvae, nematodes and gastropods. Fishes contribute to the control of makhana pests. Their faecal matter acts as organic manure for makhana crop. Plankton population fluctuated between 1260 u/l to 4030 u/l in the control pond and 1630 u/l to 4722 u/l in the experimental pond. During the grand growth period of makhana crop (April to July) the dissolved oxygen content fluctuated between 5.02 mg/l to 6.68 mg/l in the covered areas and 6.04 mg/l to 6.92 mg/l in uncovered areas. Makhana leaves acting as blanket barrier over the water surface brought down the D.O. content in the covered areas of the pond. Free CO sub(2) content showed wider fluctuation in the experimental pond (25.2 mg/l to 30.9 mg/l) than in the control pond (25.1 mg/l to 28.6 mg/l). This could be due to decomposition of plant parts of the presiding crop lying as debris at the pond bottom. Autochthonous supply of nutrients enhanced the content of nitrogen, phosphorous and organic carbon in the soil of experimental pond. The experimental pond covering an area of 0.40 ha yielded 852 kg fish and 200 kg pops whereas the control pond covering the same area produced 777 kg fish only. The net profit per ha came out to be Rs.1,04,700 and Rs. 66,200 in integrated and non-integrated system respectively. Owing to crop diversification, the present integrated system was found to be more viable than the non-integrated system in terms of production and net profit.