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

The ontogeny of haematopoiesis in the marine teleost Leiostomus xanthurus and a comparison of the site of initial haematopoiesis with Opsanus tau

The ontogeny of haematopoiesis in the perciform fish, spot Leiostomus xanthurus, differed from that reported as the norm for fishes, as exemplified by the cypriniform zebrafish Danio rerio, and observed in the batrachoidiform oyster toadfish Opsanus tau. Erythropoiesis in spot was first evident in the head kidney of yolk-sac larvae 3 days after hatching (DAH). No embryonic intermediate cell mass (ICM) of primitive stem cells or blood islands on the yolk were apparent within embryos. Erythrocytes were first evident in circulation near the completion of yolk absorption, c. 5 DAH, when larvae were c. 20 mm notochord length (LN). Erythrocyte abundance increased rapidly with larval development for c. 14 to 16 DAH, then became highly variable following changes in cardiac chamber morphology and volume. Erythrocytic haemoglobin (Hb) was not detected within whole larvae until they were 12 DAH or c. 31 mm LN, well after yolk and oil-globule absorption. The Hb was not quantified until larvae were >47 DAH or >7 mm standard length. The delayed appearance of erythrocytes and Hb in spot was similar to that reported for other marine fishes with small embryos and larvae. In oyster toadfish, a marine teleost that exhibits large embryos and larvae, the ICM and Hb were first evident in two bilateral slips of erythropoietic tissue in the embryos, c. 5 days after fertilization. Soon thereafter, erythrocytes were evident in the heart, and peripheral and vitelline circulation. Initial haematopoiesis in oyster toadfish conformed with that described for zebrafish. While the genes that code for the development of haematopoiesis are conserved among vertebrates, gene expression lacks phylogenetic pattern among fishes and appears to conform more closely with phenotypic expression related to physiological and ecological influences of overall body size and environmental oxygen availability.

Increasing the contribution of small-scale fisheries to poverty alleviation and food security

The objectives of these Technical Guidelines are to provide a focus on small-scale fisheries and their current and potential role in contributing to poverty alleviation and food security by expanding on the guidance on small-scale fisheries offered by the Code. The Guidelines are complementary to existing Technical Guidelines for Responsible Fisheries. Most small-scale fishers are in developing countries and many live in communities characterized by poverty and food insecurity. Small-scale fishing communities are faced with an array of serious problems, including overexploitation and depletion of resources, lack of alternative sources of employment, rapid population growth, migration of populations, displacement in coastal areas due to industrial development and tourism, pollution and environmental degradation and conflicts with large commercial fishing operations. However, small-scale fisheries are critical for food security and poverty alleviation in many countries. The first part of the Guidelines discusses the current contribution, role and importance of small-scale fisheries in poverty alleviation and food security. It examines the importance of small-scale fisheries for poverty alleviation at a national, local and household level. It also notes the nutritional qualities of fish and thus the particular role of fish in nutritional aspects of food security. The fact that about half of all fish caught for human consumption comes from small-scale fisheries underlines the importance of this subsector for the world fish supply. In many countries small-scale fisheries contribute to national food security both directly – where fish is a crucial part of the daily diet, and indirectly – by generating foreign exchange earnings that enable the purchase through trade of a range of food products. The second part of the Guidelines explores ways through which the contribution of small-scale fisheries to poverty alleviation and food security could be enhanced. A vision for the future of small-scale fisheries is presented as a goal towards which the subsector should develop. Ensuring greater participation by small-scale fishers and their communities in the formulation of policies, the development of related legislation and regulations, and in management decision-making and implementation processes, is vital to the realization of this vision. The central role of effective fisheries management, the importance of considering cross sectoral uses of fisheries and related resources, the special role of women in fish marketing, processing and value addition, the significant scope for trade, the critical role that adequate financing may have in enabling transitions for effective fisheries management and the role of knowledge in making informed decisions are all discussed in these Guidelines. (PDF contains 97 pages)

Artisanal canoe fishing industry of the Rivers State: its economic viability and investment potentials

Consequent upon the present national call in Nigeria for all to go back to agriculture including fishing, most retrenched workers and unemployed youths from the riverine areas are taking up fishing as a legitimate and gainful livelihood. To sustain this tempo and attract more investment, the economic viability of such projects must be known. This study is an attempt to document the profitability and investment potential of artisanal canoe fishing. Socio-economic information including catches, operational cost and returns were obtained through a personal interview questionnaire survey of 240 randomly selected artisanal canoe fishermen from Bonny, Brass and Degema Local Government Areas (LGA) of the State and analyzed. With an investment cost of about 8,135, 8,490 and 6,571 and operation cost of 750, 776 and 627, the analysis showed an average monthly gross income of 1,869, 3,221 and 1,775 for the three local government areas respectively. A benefit-cost-ratio of 1:8, net present value of 400, 603 and internal rate of return greater than 50% were obtained. Since capital invested in fisheries is not tied up for long before benefits start flowing, coupled with the high IRR, it is concluded that artisanal canoe fishing would be an economically viable venture if well managed

Parents aspiration and youth perception to sustainable fisheries development in Kainji Lake basin

Artisanal fisheries development in Nigeria, like in any other developing country of the world is characterized by subsistence level of operation using dugout canoe and paddle. This implies that parents and children constituted the labour in use since they only struggle for the upkeep of the family. A total of 240 questionnaires were used to solicit information from the respondents. This total was divided into 120 each for both parents and the youths respectively. Simple descriptive statistics such as frequency distribution and percentages were used to analyze their responses. Parents have strong aspiration for their children to succeed them hence, 78.3% of the parents expressed their aspiration for succession by the younger ones while 83.3% of parents tend to support their aspiration with persuasive strategies such as allowing their children to partake in fishing activities at will. On the part of the youth over 70% of them perceived fishing as a viable business where they can succeed their parents provided government can come to their aid in form of active involvement in the development of rural fisheries. It is therefore believed that fisheries development could achieve rapid improvement if the aspiration of the parents is balanced with perception of the youth and the government meets their expectation

Discharge and turbidity of the regulated River Tees. Variance spectrum analysis

High suspended sediment loads may be deleterious to adult salmonids and invertebrates in gravel-bedded streams. Further, the accumulation of fine material in the interstices of the gravel may have an adverse impact on the recruitment of the young stages of salmonids. It is important therefore not only to quantify the rates and degrees of silting but also to identify sediment sources and to determine both, the frequency of sediment inputs to the system and the duration of high sediment concentrations. This report explores the application of variance spectrum analysis to the isolation of sediment periodicities. For the particular river chosen for examination the method demonstrated the essentially undisturbed nature of the catchment. The regulated river chosen for examination is the River Tees in Northern England. Variance spectrum analysis was applied to a series of over 4000 paired daily turbidity and discharge readings.

A comparative study of consumption rates and preference for some species of aquatic plants by Tilapia rendalli

The daily consumption rates and preference of juvenile Tilapia rendalli for some macrophytes, Ceratophyllum demersum, Lagarosiphon major, Najas pectinatas and Valisneria aethiopica were determined. Fish were offered single macrophyte diets to determine daily consumption and a mixture of the 4 macrophytes in equal quantities to determine selection. Consumption rates were 821.50 mg, 829.05 mg, 940.00 mg and 2293.53 mg per fish per day, respectively. The differences in consumption rates were significant. Preference was shown for V.aethiopica, whilst C.demersum was least selected. Fish fed on single species lost weight whereas those fed on a variety of macrophytes gained in weight.

Changes in consumer tastes in the demand for fish and meat in Malaysia

In this article the demand for fish and its substitute was estimated using a very flexible demand function, the Almost Ideal Demand System (AIDS) developed by Deaton and Muelllbaeur (1980), incorporating the habit formation variable to measure the impact of the changes in tastes in comsumer demand for fish and meat products from 1960 to 1990 in Malaysia. Information on price and income elasticities for these meat groups was also obtained. To incorporate consumption habit variables, the dynamic translating procedure proposed by Pollak (1970) and Pollak and Wales (1981) has been adopted. The overall results of the maximum likelihood estimates of the dynamic AIDS model are quite good where 19 of 30 coefficients are significantly different from zero and the minimum budget shares, the constant, are between zero and one for each meat type. Consumers tend to purchase and consume fish, chicken, and pork almost daily. Beef and mutton are only consumed occassionally since they are relatively more expensive. This finding is consistent with the trend observed in the per capita consumption and budget share where fish, chicken, and pork tended to dominate over beef and mutton from 1960 to 1990.

A study of water quality in Baltimore Harbor

Baltimore Harbor is polluted by discharge of sewage and industrial wastes into tributary streams and peripheral waters. The Harbor is used extensively for navigation, industrial water supply, and recreation as well as for waste disposal. The degree of pollution varies from negligible in the principal fairway to severe in the innermost sections. Private industry discharges several hundred tons of acid materials daily and is also the principal source of organic pollution.