Feeding ecology of Atlantic bluefin tuna (Thunnus thynnus) in North Carolina: diet, daily ration, and consumption of Atlantic menhaden (Brevoortia tyrannus)

Diet, gastric evacuation rates, daily ration, and population-level prey demand of bluefin tuna (Thunnus thynnus) were estimated in the continental shelf waters off North Carolina. Bluefin tuna stomachs were collected from commercial fishermen during the late fall and winter months of 2003–04, 2004–05, and 2005–06. Diel patterns in mean gut fullness values were used to estimate gastric evacuation rates. Daily ration determined from mean gut fullness values and gastric evacuation rates was used, along with bluefin tuna population size and residency times, to estimate population-level consumption by bluefin tuna on Atlantic menhaden (Brevoortia tyrannus). Bluefin tuna diet (n= 448) was dominated by Atlantic menhaden; other teleosts, portunid crabs, and squid were of mostly minor importance. The time required to empty the stomach after peak gut fullness was estimated to be ~20 hours. Daily ration estimates were approximately 2% of body weight per day. At current western Atlantic population levels, bluefin tuna predation on Atlantic menhaden is minimal compared to predation by other known predators and the numbers taken in commercial harvest. Bluefin tuna appear to occupy coastal waters in North Carolina during winter to prey upon Atlantic menhaden. Thus, changes in the Atlantic menhaden stock status or distribution would alter the winter foraging locations of bluefin

Estimating consumption rates of juvenile sandbar sharks (Carcharhinus plumbeus) in Chesapeake Bay, Virginia, using a bioenergetics model*

Using a bioenergetics model, we estimated daily ration and seasonal prey consumption rates for six age classes of juvenile sandbar sharks (Carcharhinus plumbeus) in the lower Chesapeake Bay summer nursery area. The model, incorporating habitat and species-specific data on growth rates, metabolic rate, diet composition, water temperature (range 16.8−27.9°C), and population structure, predicted mean daily rations between 2.17 ±0.03 (age-0) and 1.30 ±0.02 (age-5) % body mass/day. These daily rations are higher than earlier predictions for sandbar sharks but are comparable to those for ecologically similar shark species. The total nursery population of sandbar sharks was predicted to consume ~124,000 kg of prey during their 4.5 month stay in the Chesapeake Bay nursery. The predicted consumption rates support the conclusion that juvenile sandbar sharks exert a lesser top-down effect on the Chesapeake Bay ecosystem than do teleost piscivores and hu

Fish consumption pattern in major freshwater fisheries provinces of Cambodia

Production and consumption of fish were estimated for a one year period during 1995-96 using a sample of 5 117 households. The sample was taken from a study area covering 83 sample communes in 51 fishing districts belonging to eight freshwater fisheries provinces. About 39% of households in fishing dependent communities were actively involved in fishing. Of the total fishing households, 14% took part in commercial fishing using middle-scale fishing gear. Average annual catch per household for middle-scale and family fishing was 3 319 kg and 647 kg, respectively. Nearly 40% of the fish catch was consumed within the communes. The per capita consumption of fresh fish by fishing households (49.7 kg/yr) was higher than that of non-fishing households (39.9 kg/yr). Including processed fish, the total fish consumption by the fishing dependent communes was estimated at 75.6 kg per capita per annum. Given this high rate of fish consumption, development interventions must consider the role of fisheries in ensuring a sustainable livelihood and food security to Cambodia's growing population.

Consumption to biomass (Q/B) ratio and estimates of Q/B-predictor parameters for Caribbean fishes

Estimates of the Q/B ratio and parameters of equations to 'predict' Q/B values for 116 fish stocks in the Gulf of Salamanca, Colombia are presented. A compilation of these estimates available for Caribbean Sea fishes (264 stocks) is also provided for comparison purposes. General trends in the value of Q/B resulting from differences in the equation and parameter values used are briefly discussed.

Estimating the food consumption of fishes: one step in linking a species with its ecosystem

Details are given of a new software package MAXIMS which may be used to estimate the daily food consumption of fish. The software estimates the feeding times, the rates of ingestion and evacuation and related parameters. Two applications of the program are described. The first pertains to anchovy (Engraulis ringens ) with one feeding period per day, and the second one to juvenile cod (Gadus morhua ), which feed during dawn and dusk.

Food consumption/biomass ratios of the pelagic fish community of Lake Malawi/Niassa

An empirical model relating food requirements to morphometric indices of metabolic rate was used to calculate consumption/biomass ratios (Q/B) for 16 species of fish that make the pelagic fish community in Lake Malawi/Niassa. The Q/B/year varied from 3.31 to 9.82, with the large catfish (Dinotopterus nyasensis) having the lowest and a small cyprinid (Engraulicypris sardella) having the highest Q/B ratio. Direct estimates of Q/B for four of the most abundant species, based on analysis of diel feeding patterns, ranged from 4.20 to 24.70; the extreme values in this range representing replicate studies on the same species, the predatory cichlid Rhamphochromis longiceps. Previous studies that indicated exceptionally low Q/B ratios (1.0) in pelagic cichlids from Lake Malawi are not supported by this more recent work.

Improving aquaculture feed in Bangladesh: From feed ingredients to farmer profit to safe consumption

Use of manufactured feeds in aquaculture in Bangladesh has grown rapidly over the last five years. More than 1 million tonnes of commercially formulated feeds and 0.3-0.4 million tonnes of farm-made feeds were produced in 2012, and sectoral growth is projected to increase substantially over the medium term. This working paper summarizes findings from a study, conducted as part of the WorldFish/USAID “Feed the Future-Aquaculture” project in 2012, assessing the current status of the aquaculture feed sector in Bangladesh. Fish feed value chains, market trends, ingredients and formulation systems, farm feeding practices, ancillary services and feed regulations were investigated. The study identifies a number of entry points for interventions in the sector, and investments which would improve feed quality and farmer access to better feeds and support the growth of sustainable aquaculture.

High sensitive NO2 gas sensor with low power consumption using selectively grown ZnO nanorods.

The noble gas sensor using multiple ZnO nanorods was fabricated with CMOS compatible process and sol-gel growth method on selective area and gas response characteristics to NO2 gas of the sensor device were investigated. We confirmed the sensors had high sensitive response denoted by the sensitivity of several tens for NO2 gas sensing and also showed pretty low power consumption close to 20 mW even though the recovery of resistance come up to almost the initial value.

Fish consumption by harbor seals (Phoca vitulina) in the San Juan Islands, Washington

The harbor seal (Phoca vitulina) is a large-bodied and abundant predator in the Salish Sea ecosystem, and its population has recovered since the 1970s after passage of the Marine Mammal Protection Act and the cessation of bounties. Little is known about how this large predator population may affect the recovery of fish stocks in the Salish Sea, where candidate marine protected areas are being proposed. We used a bioenergetics model to calculate baseline consumption rates in the San Juan Islands, Washington. Salmonids (Oncorhynchus spp.) and herring (Clupeidae) were the 2 most energetically important prey groups for biomass consumed by harbor seals. Estimated consumption of salmonids was 783 (±380 standard deviation [SD]) metric tons (t) in the breeding season and 675 (±388 SD t in the nonbreeding season. Estimated consumption of herring was 646 (±303 SD) t in the breeding season and 2151 (±706 SD) t in the nonbreeding season. Rockfish, a depressed fish stock currently in need of population recovery, composed one of the minor prey groups consumed by harbor seals (84 [±26 SD] t in the nonbreeding season). The variables of seal body mass and proportion of prey in seal diet explained >80% of the total variation in model outputs. Prey groups, such as rockfish, that are targeted for recovery may still be affected by even low levels of predation. This study highlights the importance of salmonids and herring for the seal population and provides a framework for refining consumption estimates and their confidence intervals with future data.

Seafood consumption and supply sources in Hawaii, 2000-2009

Measures of consumption and supply sources of seafood can provide valuable input to research and policy planning of a viable food system. This article fills a gap in the existing literature by mapping the existing seafood supply flows from various sources (local, domestic U.S., and foreign) in Hawaii. The authors trace the seafood transshipment of foreign origin via the continental United States to Hawaii and update total and per capita consumption of seafood more accurately by including noncommercial catches into the analysis. Per capita seafood consumption in Hawaii from all commercial sources is estimated at an annual average of 29 edible pounds during the 10-year period from 2000 to 2009. This is significantly more than the 16 edible pounds for all U.S consumption in 2009. Including noncommercial catch, the same measure increases to 37 edible pounds. The eight-pound differential suggests that noncommercial fishing is an important source of seafood supply in Hawaii. Overall, fresh tuna (Thunnus spp.) is the single largest species group consumed, followed by Pacific and Atlantic salmon (Salmonidae). By edible weight, the majority of Hawaii’s commercial seafood supply comes from foreign sources (57%) vs. local sources (37%), and U.S. domestic sources (6%). The leading sources for Hawaii’s direct seafood imports from 2000 to 2009, were Taiwan, Japan, New Zealand, the Philippines, and the Marshall Islands. Local supply becomes the majority source once noncommercial catch is included with 51% of the total supply.

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