Temporal Changes in a Tropical Nekton Assemblage and Performance of a Prawn Selective Gear

The temporal variation of components of a moderately diverse (H=1.46) tropical estuarine fish assemblage (long. 146°30'E, lat. 8°45'S) was directed by salinities that had been determined by local oceanographic and probably topographic conditions. For this assemblage, two types of intrayear component profiles are predicted. Pooled data (1988-91) reveal a large component of regular/resident species (43%) in an assemblage which has been under a narrow temperature regime «5T). These results facilitate a discussion on the relevance and usefulness of three hypotheses often cited in studies concerning species diversity and component characteristics of the subtropical/tropical coastal nonreef fish assemblages. Manifestations of the assemblage are reflected in catch composition and weights of 39 trials conducted for a selective prawning gear whose performance in bycatch reduction, mainly for finfishes, is judged by an index, E, we have previously proposed. This gear is capable of harvesting the prawn while conserving the demersal fish. Behavioral responses to netting of the prawns and the finfishes, especially the nearshore surface schoolers such as leiognathids, are discussed from several points of view. An adaptation in terms of group selection for leiognathids of their locking mechanism of median fin spines has been interpreted. For the purpose of bycatch reduction or E enhancement, suggestions for improvements in net design and trawl configuration by considering the behavioral features of fish are made. Our original formula of E is modified for general use. Bycatch problems in the regional prawn fisheries and their possible impacts on fishery planning and development in Papua New Guinea as a developing country are discussed. The gear tested may offer enormous ecological and economic benefits. The gear is multipurpose, extremely simple, and can also be used as a biological sampler.

Effect of feed quality restriction followed by realimentation on growth, nutrient utilization, biochemical changes and haematological profiles of Indian major carp, rohu (Labeo rohita H.)

To investigate the effect of protein restriction with subsequent re-alimentation on nutrient utilization, hematological and biochemical changes of Indian major carp, Rohu (Labeo rohita H.), 150 acclimatized Rohu fingerlings (average 20.74 ± 0.13 g) divided into five experimental groups (30 fingerlings in each groups with three replications with 10 fingerlings in each) for experimental trial of 90 days using completely randomized design. Control group (T sub(CPR)) was fed with feed having 30% crude protein at 3% of body weight for 90 days trial period. Other experimental groups T sub(1PR) was alternatively 3 days fed with feed having 20% CP and 30% CP at 3% of body weight, T sub(2PR) was alternatively 7 days fed with feed having 20% CP and 30% CP at 3% of body weight, T sub(3PR) was alternatively 15 days fed with feed having 20% CP and 30% CP at 3% of body weight and T sub(4PR) was alternatively 25 days fed with feed having 20% CP and 30% CP at 3% of body weight during 90 days trial period with daily ration in two equal halves at morning and afternoon. It was noticed that retention of different nutrients was almost similar among all treatment groups indicated improvement of digestibility of nutrients might not be the mechanisms for recovery growth in carps. Increased percent feed intake of body weight (hyperphagia) (4.14 ± 0.30 or 4.94 ± 0.46 and 3.33 ± 0.29), improved specific growth rate (1.86 ± 0.09 or 2.26 ± 0.05 and 1.43 ± 0.01), absolute growth rate (1.57 ± 0.08 or 1.84 ± 0.18 and 1.36 ± 0.12), protein efficiency ratio (1.19 ± 0.11 or1.16 ± 0.12 and 1.05 ± 0.09) were the important mechanism showing better performance index (21.60 ± 1.09 or 23.80 ± 0.21 and 19.45 ± 0.37) through which the experimental groups which were protein restricted and re-alimented at 3 or 7 days alternatively during 90 days trial period could able to compensate the growth retardation and to catch up the final body weight of control (128.68 ± 11.53 g/f) but other experimental groups failed to compensate during 90 days trial period. Result of the present study indicated that deprived fish i.e., fish received alternate 3 or 7 days protein restriction and re-alimentation showed recovery growth had still lower values of Hb (10.21 ± 0.02, and 9.88 ± 0.04 g/dl), hematocrit value (30.62 ± 0.05 and 26.64 ± 0.11%), total erythrocytic count (3.40 ± 0.01 and 3.29 ± 0.01 X10super(6) mm³), plasma glucose (126.93 ± 0.20 and 126.67 ± 0.05 mg/dl), total plasma lipid (1.04 ± 0.01 and 1.02 ± 0.01 g/dl) and liver glycogen (290.10 ± 0.80 and 288.99 ± 0.95 mg/kg) in comparison to control (10.56 ± 0.08 g/dl, 31.68 ± 0.24%, 3.52 ± 0.03 X10super(6) mm³, 128.23 ± 0.25 mg/dl, 1.07 ± 0.01g/dl and 292.00 ± 0.23 mg/kg) at the end of 90 days trial but total plasma protein in deprived group was compensated with advancement of trial period. All hematological and biochemical parameters studied were proportionately lowered in the experimental group got higher degree of deprivation. These findings suggested that with the increase of trial length complete compensation of hematological and biochemical profiles of rohu might be achieved. The results indicated that the implementation of alternative 7 days low and high protein diet feeding during aquaculture of carps could make economize the operation through minimizing the feed input cost.