Abundance, condition, and diet of juvenile Pacific ocean perch (Sebastes alutus) in the Aleutian Islands

T he relative value of pelagic habitat for three size classes of juvenile Pacific ocean perch (Sebastes alutus) was investigated by comparing their abundance and condition in two areas of the Aleutian Islands. Diet, zooplankton biomass, and water column temperatures were examined as potential factors affecting observed differences. Juvenile Pacific ocean perch abundance and condition, and zooplankton biomass varied significantly between areas, whereas juvenile Pacific ocean perch diet varied only by size class. Observed differences in fish condition may have been due to the quantity or quality of pelagic prey items consumed. For the delineation of essential demersal fish habitat, important ecological features of the pelagic habitat must therefore be considered.

Decline in condition of northern bluefin tuna (Thunnus thynnus) in the Gulf of Maine

The northern bluefin tuna (Thunnus thynnus) is a highly mobile apex predator in the Gulf of Maine. Despite current stock assessments that indicate historically high abundance of its main prey, Atlantic herring (Clupea harengus), commercial fishermen have observed declines in the somatic condition of northern bluefin tuna during the last decade. We examined this claim by reviewing detailed logbooks of northern bluefin tuna condition from a local fishermen’s cooperative and applying multinomial regression, a robust tool for exploring how a categorical variable may be related to other variables of interest. The data set contained >3082 observations of condition (fat and oil content and fish shape) from fish landed between 1991 and 2004. Energy from stored lipids is used for migration and reproduction; therefore a reduction in energy acquisition on bluefin tuna feeding grounds could diminish allocations to growth and gamete production and have detrimental consequences for rebuilding the western Atlantic population. A decline in northern bluefin tuna somatic condition could indicate substantial changes in the bottom-up transfer of energy in the Gulf of Maine, shifts in their reproductive or migratory patterns, impacts of fishing pressure, or synergistic effects from multiple causes.

The structure and margins of the Lake Chilwa fisheries in Malawi: a value chain analysis

Small freshwater pelagic fisheries in closed lakes are very important to millions of people in sub-Saharan Africa providing livelihoods and nutritional security. However, returns from these fisheries have been shown to �uctuate in response to climatic variability. In order to understand the impact of these fluctuations on the livelihoods of people dependant on these fisheries, there is a need for information on how the fish value chain is organized and how it functions in response to variation in supplies. The results will feed into strategies that build resilience in fishing households against the uncertainties arising from unstable ecosystems. The Lake Chilwa fishery value chain is composed of fishers, processors, traders, fish transporters, boat owners, owners of fish processing shades, fisheries associations, gear owners, gear makers, firewood sellers, and traders of fishing gear and equipment. The value chain employs many people and local authorities can consider using this information in the design of rural development strategies for employment generation in small-scale fishing communities. The findings from this study have a number of implications for the improvement of the livelihood of fishers and enhancing their capacity to mitigate against the effects of climate change.

Length-weight relationship and relative condition of Heterobranchus longifilis (Valenciennes) from Idodo River, Nigeria

Length-weight relationship parameters of Heterobranchus longifilis males, females and combined sexes are given. The samples were collected from Idodo River, with size ranging from 123 mm total length, L, to 936 mm L. The values obtained for the mean L by sex show that males were significantly (p<0.05) larger than females. The results show that the slope (b) is significantly (p<0.05) below 3.0 for the male, female and pooled sample. The species exhibit a negative allometric growth pattern. The relative condition of fish shows seasonal variation, with females generally being in better condition than the males.

Molecular probes and polymerase chain reaction (PCR) -based kits for diagnosis of shrimp diseases

Technology for effective and fast diagnosis of animal diseases is essential for developing aquaculture management strategies. This paper reviews the conventional techniques for shrimp disease diagnosis and discusses the emergence of nuclei acid probes and polymerase chain reaction (PCR)-based kits as powerful tools for rapid and accurate detection of shrimp diseases.

Distribution, feeding condition, and growth of Japanese Spanish mackerel (Scomberomorus niphonius) larvae in the Seto Inland Sea

Distribution of eggs and larvae and feeding and growth of larvae of Japanese Spanish mackerel (Scomberomorus niphonius) were investigated in relation to their prey in the Sea of Hiuchi, the Seto Inland Sea, Japan, in 1995 and 1996. The abundance of S. niphonius eggs and larvae peaked in late May, corresponding with that of clupeid larvae, the major prey organisms of S. niphonius larvae. The eggs were abundant in the northwestern waters and the larvae were abundant in the southern waters in late May in both years, indicating a southward drift during egg and yolksac stages by residual f low in the central part of the Sea of Hiuchi. Abundance of clupeid larvae in southern waters, where S. niphonius larvae were abundant, may indicate a spawning strategy on the part of first-feeding S. niphonius larvae to encounter the spatial and temporal peak in ichthyoplankton prey abundance in the Seto Inland Sea. Abundance of the clupeid larvae was higher in 1995 than in 1996. Feeding incidence (percentage of stomachs with food; 85.3% in 1995 and 67.7% in 1996) and mean growth rate estimated from otolith daily increments (1.05 mm/d in 1995 and 0.85 mm/d in 1996) of S. niphonius larvae in late May were significantly higher in 1995. Young-of-the-year S. niphonius abundance and catch per unit of fishing effort of 1-year-old S. niphonius in the Sea of Hiuchi was higher in 1995, indicating a more successful recruitment in this year. Spatial and temporal correspondence with high ichthyoplankton prey concentration was considered one of the important determinants for the feeding success, growth, and survival of S. niphonius larvae.

Analysis of the retailer value chain segment in five governorates

This study is the third output of the SDC-funded “Improving Employment and Income through Development of Egyptian Aquaculture” (IEIDEAS), a three-year project being jointly implemented by the WorldFish Center and CARE International in Egypt with support from the Ministry of Agriculture and Land Reclamation. The aim of the study is to gather data on the retailer segment of the aquaculture value chain in Egypt, namely on the employment and market conditions of the women fish retailers in the five target governorates. In addition, this study provides a case study in Minya and Fayoum of the current income levels and standards of living of this target group. Finally, the study aims to identify the major problems and obstacles facing these women retailers and suggest some relevant interventions.

Assessment of the carp seeds value chain in southern Bangladesh (final draft)

The Aquaculture for Income and Nutrition (AIN) project implemented by World Fish and funded by USAID, aims at increasing aquaculture production in 20 districts of Southern Bangladesh (Greater Khulna, Greater Barisal, Greater Jessore and Greater Faridpur) to reduce poverty and enhance nutritional status. As part of its initial scoping activities World Fish commissioned this value chain assessment on the market chains of carp fish seed (spawn, fry and fingerlings) in the southern region of Bangladesh. The purpose of this study is to obtain a clearer understanding of the volumes of fish produced and consumed in Southern Bangladesh and their origin (by system and location), their destination (by type of market, type of consumer and location), and to gain a clearer understanding of potential market based solutions to farmer’s problems, which the project could implement.

Value chain analysis: shrimp, prawn and tilapia from the southern region of Bangladesh & feasibility analysis: brackish water sea-bass in the southern region in Bangladesh

The WorldFish Center is implementing the FtF Aquaculture Project in 20 southern districts in Bangladesh. The project is implemented under USAID’s Feed the Future initiative in collaboration with the Government of Bangladesh. The project contributes to achieving the ‘Feed the Future’ goals through four objectives: (i) dissemination of improved quality fish and shrimp seed, (ii) improving the nutrition and income status of farm households, (iii) increasing investment, employment and fish production through commercial aquaculture and (iv) policy and regulatory reform and institutional capacity building to support sustainable aquaculture growth. The project commissioned this study to gather insights into the value chains of shrimp, prawn and tilapia in the project region and the feasibility of promoting culture of brackish water sea-bass in the region. The findings and recommendations are expected to provide the foundation for the project to design its interventions for achieving its goals.

The ecological condition of estuaries in the Gulf of Mexico

This document is intended for use by scientists and other citizens concerned with the ecological condition of estuaries, as well as by managers and lawmakers interested in the sustained use of estuaries for commercial and recreational purposes. It also addresses public concerns about the aesthetic quality of coastal areas vital to tourism and recreation. By producing this report on the ecological condition of estuaries in the Gulf of Mexico, we have taken one step in assessing the health of this environmental resource. We have produced an environmental report card to be used as a guide in the evaluation of management decisions and research directions. This report is organized in three parts: (1) an introduction that gives background information on the Gulf of Mexico, estuarine ecology, and the factors that impact estuaries in the gulf, (2) the main section on priority ecological indicators used to measure the condition of estuaries in the gulf and (3) an ecological report card that summarizes the data on ecological indicators and provides a rating of the condition of estuaries in each gulf state and for gulf estuaries overall. Many of the ratings were based on the percent area of estuaries in each state exhibiting degraded or adverse levels of an indicator.

Effects of pot fishing on the physical condition of snow crab (Chionoecetes opilio) and southern Tanner crab (Chionoecetes bairdi)

The effects of commercial fishing with crab pots on the physical condition of the snow crab (Chionoecetes opilio) and southern Tanner crab (C. bairdi) were investigated in the Bering Sea and in Russian waters of the Sea of Okhotsk. In crabs that were subjected to pot hauling, the presence of gas embolism and the deformation of gill lamellae were found in histopathological investigations. Crab vitality, which was characterized subjectively through observation of behavioral responses, depended on not only the number of pot hauls but also the time between hauls. Immediately after repeated pot hauls at short time intervals (≤3 days), we observed a rapid decline in vitality of crabs. When hauling intervals were increased to >3 days, the condition of crabs did not significantly change. After repeated pot hauls, concentration of the respiratory pigment hemocyanin ([Hc]) was often lower in the hemolymph of crabs than in the hemolymph of freshly caught animals. Our research indicated that changes in [Hc] in crabs after repeated pot hauls were caused by the effects of decompression and not by starvation of crabs in pots or exposure of crabs to air. We suggest that the decrease in [Hc] in hemolymph of snow and southern Tanner crabs was a response to the adverse effects of decompression and air-bubble disease. The decrease in [Hc] in affected crabs may be a result of mechanisms that regulate internal pressure in damaged gills to optimize respiratory circulation.

Using measurements of muscle cell nuclear RNA with flow cytometry to improve assessment of larval condition of Walleye Pollock (Gadus chalcogrammus)

Nuclear RNA and DNA in muscle cell nuclei of laboratory-reared larvae of Walleye Pollock (Gadus chalcogrammus) were simultaneously measured through the use of flow cytometry for cell-cycle analysis during 2009–11. The addition of nuclear RNA as a covariate increased by 4% the classification accuracy of a discriminant analysis model that used cell-cycle, temperature, and standard length to measure larval condition, compared with a model without it. The greatest improvement, a 7% increase in accuracy, was observed for small larvae (<6.00 mm). Nuclear RNA content varied with rearing temperature, increasing as temperature decreased. There was a loss of DNA when larvae were frozen and thawed because the percentage of cells in the DNA synthesis cell-cycle phase decreased, but DNA content was stable during storage of frozen tissue.