Prey consumption of Steller sea lions (Eumetopias jubatus) off Alaska: How much prey do they require?

The effects of seasonal and regional differences in diet composition on the food requirements of Steller sea lions (Eumetopias jubatus) were estimated by using a bioenergetic model. The model considered differences in the energy density of the prey, and differences in digestive efficiency and the heat increment of feeding of different diets. The model predicted that Steller sea lions in southeast Alaska required 45–60% more food per day in early spring (March) than after the breeding season in late summer (August) because of seasonal changes in the energy density of the diets (along with seasonal changes in energy requirements). The southeast Alaska population, at 23,000 (±1660 SD) animals (all ages), consumed an estimated 140,000 (±27,800) t of prey in 1998. In contrast, we estimated that the 51,000 (±3680) animals making up the western Alaska population in the Gulf of Alaska and Aleutian Islands consumed just over twice this amount (303,000 [±57,500] t). In terms of biomass removed in 1998 from Alaskan waters, we estimated that Steller sea lions accounted for about 5% of the natural mortality of gadids (pollock and cod) and up to 75% of the natural mortality of hexagrammids (adult Atka mackerel). These two groups of species were consumed in higher amounts than any other. The predicted average daily food requirement per individual ranged from 16 (±2.8) to 20 (±3.6) kg (all ages combined). Per capita food requirements differed by as much as 24% between regions of Alaska depending on the relative amounts of low–energy-density prey (e.g. gadids) versus high–energy-density prey (e.g. forage fish and salmon) consumed. Estimated requirements were highest in regions where Steller sea lions consumed higher proportions of low–energy-density prey and experienced the highest rates of population decline

Food habits and consumption rates of common dolphinfish (Coryphaena hippurus) in the eastern Pacific Ocean

An ecosystem approach to fisheries management requires an understanding of the impact of predatory fishes on the underlying prey resources. Defining trophic connections and measuring rates of food consumption by apex predators lays the groundwork for gaining insight into the role of predators and commercial fisheries in influencing food web structure and ecosystem dynamics.We analyzed the stomach contents of 545 common dolphinfish (Coryphaena hippurus) sampled from 74 sets of tuna purse-seine vessels fishing in the eastern Pacific Ocean (EPO) over a 22-month period. Stomach fullness of these dolphinfish and digestion state of the prey indicated that diel feeding periodicity varied by area and may be related to the digestibility and energy content of the prey. Common dolphinfish in the EPO appear to feed at night, as well as during the daytime. We analyzed prey importance by weight, numbers, and frequency of occurrence for five regions of the EPO. Prey importance varied by area. Flyingfishes, epipelagic cephalopods, tetraodontiform fishes, several mesopelagic fishes, Auxis spp., and gempylid fishes predominated in the diet. Ratios of prey length to predator length ranged from 0.014 to 0.720. Consumption-rate estimates averaged 5.6% of body weight per day. Stratified by sex, area, and length class, daily rations ranged up to 9.6% for large males and up to 19.8% for small dolphinfish in the east area (0–15°N, 111°W–coastline). Because common dolphinfish exert substantial predation pressure on several important prey groups, we concluded that their feeding ecology provides important clues to the pelagic food web and ecosystem structure in the EPO.

Effect of salinity on food consumption and growth of juvenile Nile tilapia (Oreochromi niloticus L.)

The effect of salinity (0, lO and 20%o, water temperature 28 ± l oC) on food consumption and growth of juvenile Nile tilapia, Oreochromis niloticus L. (9.94 ± 0.15 g) were investigated by feeding group of 20 fish at 2% body weight day. Individual food consumption was measured using X-radiography. There were no significant differences in growth or white muscle protein concentrations among groups. During feed deprivation, weight loss was similar for fish held at O%o and 10 %o salinity, but after 7 days over 50% of the fish maintained at 20%o salinity developed lesions covering 5-25% of the body. No significant relationships were observed between individual specific growth rates and food consumption rates within the groups. The fish in all salinity groups showed a negative correlation between specific growth rate and food conversion ratio. The coefficient of variation for wet weight specific food consumption and the mean share of meal for each fish were used as a measure of social hierarchy strength. A negative correlation was observed between coefficient of variation in food consumption and mean share of meal. The social hierarchy structure was similar in all salinities; 25% of the fish were dominant (18.29% above an equal share of meal) and 30% were subordinate (16.19% below an equal share of meal) and the remainder 45% fish fed theoretical share of meal (MSM, 5.26%).

Household consumption pattern and buying behavior for fish in an area Mymensingh, Bangladesh

The study was conducted on 238 households in Bangladesh Agricultural University campus and its adjoining areas in Mymensingh. The household were divided into four groups based on their per capita income. Monthly expenditure on fish, income elasticity of demand and marginal propensity to consume were calculated. 'Weighted average' method was used to study the level of preference for fish by sex and age groups and frequency of its purchase. The per capita monthly expenditure on fish of overall households was found to be Tk. 178.83. The consumption increased considerably between and among the income groups rising from Tk. 63.95 in the lowest income group to Tk. 249.11 in the highest income group. Based on income elasticity the proportion of income spent on fish was found to be greater than the proportion of increase in income for lower middle and upper middle income groups. However, percent expenditure decreased from 8.15 in lowest to 5.49 in the highest income group. Female members between 20 and 40yrs had the highest preference for fish in general followed by male members of above 40 yrs. Children (0 to 8 yrs), on the other band, had the least preference for fish, Sing and Magur (Catfishes) were the most preferred fish species for each age and sex group. Rui, a carp, was the single most purchased fish while the introduced exotic fishes were the least bought. Freshness was found to be the most important factor followed by the appearance and taste perception that positively affected the fish purchase.

Effect of benzocaine on opercular movement and oxygen consumption in Channa punctatus (Bloch)

Effect of anaesthetization with benzocaine at the rate of 18.0 mg.1super(-1) on juveniles of Channa punctatus was observed using a cylindrical glass respirometer. Oxygen consumption and opercular movement were studied at 3h and 24h of anaesthetization. The oxygen consumption of control fish increased linearly from 0.183±0.029 to 0.481±0.034 mlO sub(2).h super(-1) with an increase in body weight from 1.45±0.18 to 6.12±0.11g and showed a reduction (p<0.001) of about 41% in 3h and 37% in 24h anaesthetization of Benzocaine. Similarly, the opercular movement of control fish ranging between 46±1 to 49±1min super(-1) came down to show a reduction (p<0.001) of 43% and 38% respectively in 3h and 24h anaesthetization. The information is useful in calculation of oxygen requirement of this species for live transportation and other experimental purpose.

Parameter measurement for heavy-vehicle fuel consumption modelling

A mathematical model is developed to predict the energy consumption of a heavy vehicle. It includes the important factors of heavy-vehicle energy consumption, namely engine and drivetrain performances, losses due to accessories, aerodynamic drag, rolling resistance, road gradients, and driver behaviour. Novel low-cost testing methods were developed to determine engine and drivetrain characteristics. A simple drive cycle was used to validate the model. The model is able to predict the fuel use for a 371 tractor-semitrailer vehicle over a 4 km drive cycle within 1 per cent. This paper demonstrates that accurate and reliable vehicle benchmarking and model parameter measurement can be achieved without expensive equipment overheads, e.g. engine and chassis dynamometers.

Illegal fishing of inland water bodies of Nigeria: Kainji experience

It is a common knowledge that illegal fishing which includes use of wrong gears, explosives, excessive exploitation of choice stocks, enhancement and stocking of water body and pollution has devastating effects on the critical biomass of fish biodiversity and livelihood activities associated with fishing. Efforts worldwide to arrest these menace are significant because it has been found that illegal fishing has made fishing non sustainable, resulted in poor fishermen catches, and exacerbated the use of illegal gears in an effort to a must catch. Conflict between fisher folk and policies has continued to generate different strategies in the control of illegal fishing. Some of these strategies at regional and National levels include creation and implementation of fisheries laws, fishing edicts, code of conduct for responsible fisheries, policing of inland water bodies, capacity building and capability through training of fishermen, creating necessary awareness, arrest and punishment of offenders. There are also other initiative on conservation and management of freshwater ecosystems which have interrelation with illegal fishing. This paper examines efforts in promoting and boosting the fisheries of Lake Kainji, through creating necessary awareness, campaign visits, radio programmes, gear control, reward systems, integration and diversification of livelihood activities, community based management and policing. It further analyses what is working, problems, and prospect of fisheries laws, the need to integrate factors of political policies, other global initiative on water management for people and nature. Recommendations on strategies including protection of fishing grounds, establishment of catch data base, integration of other intervention as alternative source of income to enhance livelihood, reduce fishing pressure, and capacity building of fisher folks, development of rules and regulations that is community based are highlighted.

Mapping of the Indian fisheries growth rate and fish consumption through GIS

In the present study, Indian fisheries growth rate and fish consumption have been analyzed through GIS mapping. The analyses were based on the state-level fisheries data of India collected from the secondary sources. Accordingly, the paper contains one thematic map containing two layers. To achieve this, all the data have been brought into a tabular form through Microsoft Excel and then joined to Map Info Professional Version 8.0 GIS software with digitized map of India for further analysis to generate thematic maps. In this thematic map, the first Jayer represents the growth-rate of fish production for the period 1990-2004 and the second layer represents fish consumption for the year 2003. The thematic map represented in graphic form presents inland, marine and total growth rates, and also the rural and urban fish consumption at the state levels. This study will be useful to fish traders, planners, researchers and administrators in fisheries policy formulation for sustainable development.

Consumption pattern and consumer preference for value-added fish and fish products in north zone of India

Present paper attempts to analyze consumption pattern and consumer preferences towards value-added fish and fish products in north zone of India. Results reveal that socio economic variables affect consumption of value-added fish and fish products. A total of 49 percent respondents were of middle age group (35 to 50 years). All were literates except 7% from the rural area. All were purchasing fish at least once in 15 days. A total of 90% respondents in rural, 11% in semi urban and 50% in urban area were unaware of value-added fish and fish products. About 10% of respondents had consumed it, out of which most were from urban area. Demand analysis by Cobb Douglas (CD) Demand function revealed that when price of fish, price of the substitutes, income of family and family size were used as independent variables, variation in demand of fish explained by CD Demand function was about 39% in urban area, 24% in semi urban area and 22% in rural area. From Garette ranking technique major problems in fish consumption found were irregular supply, lack of fresh fish, high price and presence of bones in fish. While lack of awareness, unavailability, no preference and unacceptable taste were major problems for consumption of value-added fish and fish products.