Efficiency of bycatch reduction devices in small otter trawls used in the Florida shrimp fishery

Two bycatch reduction devices (BRDs)—the extended mesh funnel (EMF) and the Florida fisheye (FFE)—were evaluated in otter trawls with net mouth circumferences of 14 m, 17 m, and 20 m and total net areas of 45 m2. Each test net was towed 20 times in parallel with a control net that had the same dimensions and configuration but no BRD. Both BRDs were tested at night during fall 1996 and winter 1997 in Tampa Bay, Florida. Usually, the bycatch was composed principally of finfish (44 species were captured); horseshoe crabs and blue crabs seasonally predominated in some trawls. Ten finfish species composed 92% of the total finfish catch; commercially or recreationally valuable species accounted for 7% of the catch. Mean finfish size in the BRD-equipped nets was usually slightly smaller than that in the control nets. Compared with the corresponding control nets, both biomass and number of finfish were almost always less in the BRD-equipped nets but neither shrimp number nor biomass were significantly reduced. The differences in proportions of both shrimp and finfish catch between the BRD-equipped and control nets varied between seasons and among net sizes, and differences in finfish catch were specific for each BRD type and season. In winter, shrimp catch was highest and size range of shrimp was greater than in fall. Season-specific differences in shrimp catch among the BRD types occurred only in the 14-m, EMF nets. Finfish bycatch species composition was also highly seasonal; each species was captured mainly during only one season. However, regardless of the finfish composition, the shrimp catch was relatively constant. In part as a result of this study, the State of Florida now requires the use of BRDs in state waters.

Current velocity and catch efficiency in sampling settlement-stage larvae of coral-reef fishes

Light traps and channel nets are fixed-position devices that involve active and passive sampling, respectively, in the collection of settlement-stage larvae of coral-reef fishes. We compared the abundance, taxonomic composition, and size of such larvae caught by each device deployed simultaneously near two sites that differed substantially in current velocity. Light traps were more selective taxonomically, and the two sampling devices differed significantly in the abundance but not size of taxa caught. Most importantly, light traps and channel nets differed greatly in their catch efficiency between sites: light traps were ineffective in collecting larvae at the relatively high-current site, and channel nets were less efficient in collecting larvae at the low-current site. Use of only one of these sampling methods would clearly result in biased and inaccurate estimates of the spatial variation in larval abundance among locations that differ in current velocity. When selecting a larval sampling device, one must consider not only how well a particular taxon may be represented, but also the environmental conditions under which the device will be deployed.

Value chain analysis of the Egyptian aquaculture feed industry

The commercial aquaculture feed industry in Egypt is growing at a rapid rate. As a result, the number of fish feed mills has increased from just 5 mills producing about 20,000 t per year in 1999, to over 60 mills with a current production estimate of 800,000–1,000,000 t/year. The performance of the aquafeed industry in Egypt is not well understood, as the value chain structure has not yet been mapped. This study aims to assess the status of the fish feed sector in Egypt, with an emphasis on: mapping and understanding fish feed value chains, describing the main actors and stakeholders within the chain, assessing value chain performance, identifying major strengths and weakness of the sector, and suggesting appropriate actions, management and development strategies.

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.

Community metabolism, P/R ratio and photosynthetic efficiency of a brackishwater farm

The productivity level of a brackishwater fish culture farm consisting of 25 ponds, with a water spread area of 2.5 ha, was studied. Gross community photosynthesis of the farm was found to be 46.32 Kcal/m2/day, which is equivalent to the release of 13.23 of O2/m2/day, or the fixing of 4.10 gC/m2/day. Respiratory demand of the farm was estimated to be 44.66 kcal/m2/day, which is equivalent to the uptake of 12.76 g O2/m2/day or the utilization of 3.95 gC/m2/day. Photosynthetic efficiency of the farm was high at 2.26%. The P/R ratio was 1.04, showing eutrophic nature.

The effect of mesh size on the fishing efficiency of sardine gill nets

The study deals with the effect of mesh size on the fishing power of gill nets. The authors have shown that there can be substantial difference in the out puts of sardine gill nets, of identical design and rigging, but of different mesh sizes, operated under the same conditions.

Preliminary experiments to evaluate the relative efficiency of different natural baits in line fishing

A series of experimental hand-line fishing operations were conducted off the Madras coast employing five different types of natural fish baits. Based on the total catch of fish per day of fishing under each type of bait used, a comparative study on the catching efficiency of the different natural fish-baits was made. The reaction of the fish to particular bait appears to be the result of a complex process. Live baits have the maximum catching efficiency as seen from the fish landings when live prawns were employed as the bait. The procurement of live baits is a serious problem to the fishermen and as such suitable artificial fish lures can be profitably employed.

An interpretation of the data from "The effect of mesh size on the fishing efficiency of sardine gill nets"

The paper "The effect of mesh size on the fishing efficiency of sardine gill nets" [K.M. Joseph and A.V. Sebastian, Fish. Tech; 1(2), 180-182 (1964)] marks an important step in the progress of fisheries technology and biology in India.

On the relative efficiency of different shaped otter boards

Rectangular, horizontal curved and oval otter boards were tested under identical fishing conditions and their relative efficiency ascertained on the basis of towing tension and the horizontal opening of the boards. While the tension in the warps with the different otter boards was not significant, the horizontal curved board gave increased lateral spread to the net.

On the comparative efficiency of conventional and bulged belly fish trawls

To ensure a greater vertical opening while under tow, a trawl net with a bulged belly was made and compared with a conventional design under actual fishing conditions. It was found that the new design landed 31.8% more fish. Since the percentage lateral spread was relatively less for the bulged belly net, it was inferred that this net had higher head line height, while under operation and this was further substantiated by a greater catch of off—bottom fishes. Further, half the quantity of twine can be saved by changing the conventional trawl to that of bulged belly type.

On the relative catch efficiency of different shaped otter boards in bottom trawling

Three different types of otter boards varying in shape were tried to find out their relative catch efficiency. They were operated with two types of nets. The results indicated that the curved otter boards gave more catch per unit effort with all the combinations of nets and riggings tried.

Comparative fishing ability and economic efficiency of mechanised trawlers operating along the Kerala coast

This study was undertaken with a view to finding out the comparative fishing ability and economic performance of different fishing vessel sizes 9.15m (30'), 9.76m (32') and 10.97m (36') designed by the Central Institute of Fisheries Technology and operating along the Kerala coast. Data were collected from selected vessels of these sizes for four consecutive fishing seasons from 1964-65 to 1967-68. The catch/unit effort and total effort per year for the 10.97m (36') vessels were much better than those for the 9.76m (32') vessels. The yearly landings and the crew remuneration for the former were about twice those of the 9.76m (32') vessels. The economic efficiency of the 10.97m (36') vessels was also much better. The decline in landings per year in both size groups was more due to the reduction in the effort per year than the decline in catch/unit effort.

Effect of supplementary feed on the growth of shinghi (Heteropneustes fossilis Bloch)

Effect of two supplementary feed (food A and food B) on the growth of shinghi, Heteropneustes fossilis was observed for 3 months period during winter and summer. Food B containing rice bran 2 g, wheat bran 2 g and blood 10 ml, showed better growth. The net gain in length was 70.04 mm and in weight was 13.82 g. Total net production was observed as 254.00 g/m² with feed A and 345.50 g/m² with feed B.