Ideotyping integrated aquaculture systems to balance soil nutrients.

Due to growing land scarcity and lack of nutrient inputs, African farmers switched from shifting cultivation to continuous cropping and extended crop area by bringing fragile lands such as river banks and hill slopes into production. This accelerated soil fertility decline caused by erosion, harvesting and insufficient nutrient replenishment. We explored the feasibility to reduce nutrient depletion by increasing nutrient utilization efficiencies, while diversifying and increasing food production through the development of integrated aquaculture – agriculture (IAA). Considering the climatic conditions prevailing in Kenyan highlands, aquaculture production scenarios were ideotyped per agro-ecological zone. These aquaculture production scenarios were integrated into existing NUTrient MONitoring (NUTMON) farm surveydata for the area. The nutrient balances and flows of the resulting IAA-systems were compared to present land use.The effects of IAA development on nutrient depletion and total food production were evaluated. With the development of IAA systems, nutrient depletion rates dropped by 23–35%, agricultural production increased by 2–26% and overall farm food production increased by 22–70%. The study demonstrates that from a bio-physical point of view, the development of IAA-systems in Africa is technically possible and could raise soil fertility and total farm production. Further studies that evaluate the economic feasibility and impacts on the livelihood of farming households are recommended

Escapement of the Cape rock lobster (Jasus lalandii ) through the mesh and entrance of commercial traps

Metal-framed traps covered with polyethylene mesh used in the fishery for the South African Cape rock lobster (Jasus lalandii) incidentally capture large numbers of undersize (<75 mm CL) specimens. Air-exposure, handling, and release procedures affect captured rock lobsters and reduce the productivity of the stock, which is heavily fished. Optimally, traps should retain legalsize rock lobsters and allow sublegal animals to escape before traps are hauled. Escapement, based on lobster morphometric measurements, through meshes of 62 mm, 75 mm, and 100 mm was investigated theoretically under controlled conditions in an aquarium, and during field trials. SELECT models were used to model escapement, wherever appropriate. Size-selectivity curves based on the logistic model fitted the aquarium and field data better than asymmetrical Richards curves. The lobster length at 50% retention (L50) on the escapement curve for 100-mm mesh in the aquarium (75.5 mm CL) approximated the minimum legal size (75 mm CL); however estimates of L50 increased to 77.4 mm in field trials where trapentrances were sealed, and to 82.2 mm where trap-entrances were open. Therfore, rock lobsters that cannot escape through the mesh of sealed field traps do so through the trap entrance of open traps. By contrast, the wider selection range and lower L25 of field, compared to aquarium, trials (SR = 8.2 mm vs. 2.6 mm; L25 =73.4 mm vs. 74.1 mm), indicate that small lobsters that should be able to escape from 100-mm mesh traps do not always do so. Escapement from 62-mm mesh traps with open entrance funnels increased by 40−60% over sealed traps. The findings of this study with a known size distribution, are related to those of a recent indirect (comparative) study for the same species, and implications for trap surveys, commercial catch rates, and ghost fishing are discussed

Innovating out of the Fishmeal Trap: The role of Insect-Based Fish Feed in Consumers’ Preferences for Fish Attributes

The purpose of the study was to examine the potential market impacts of the use of insect-based protein for fish feed as an innovative approach out of the fish-meal trap. An online questionnaire was used to elicit information on fish consumption choices among 610 German consumers using a Discrete Choice Experiment. Mixed logit and latent class logit models were used to model consumers’ preference heterogeneity. Results showed, that consumers’ preferences for fish attributes such as filets, freshness, ecolabelling and domestic production are heterogeneous and important in consumption choices. The minor share of the respondents was sensitive, while the remaining was indifferent regarding the use of insect based protein as feed in trout production. For this sensitive segment, consumption would be expected to be reduced unless the price is reduced or other attributes such as convenience aspects are improved. The implication is that firms can substitute without a significant impact on the market demand given that the majority of consumers are indifferent regarding feed sources for trout production. As a result, it provides an innovative way to ensure sustainable use of resources and reduces the threat of fish meal trap while reducing pressure on the already over-exploited marine life. The results provide first insights into the market impact of using insects in the animal protein value chain. It is important especially with Europe’s recent lift of the ban on using insect-based protein in the animal food industry

Analysis of Gray Fox (Urocyon cinereoargenteus) Fur Harvests in Arkansas

An investigation was conducted on gray fox (Urocyon cinereoargenteus) fur harvest in Arkansas. Data were gathered from a mail survey of Arkansas trappers and from Arkansas Game and Fish Commission fur harvest records from 1939 to 1983. Analyses of these data demonstrated: 1) gray fox were abundant statewide with lower levels in the Delta region; 2) there was a need for fox trappers to keep better records on their trapping efforts, success and composition of catch, including sex and age data; 3) market price: harvest correlation was high (r = 0.956, p \u3c .001); 4) over the past 10 years, the Ozark Mountain region provided the greatest contribution to annual fox harvests, the Ouachita Mountain and Gulf Coastal Plain regions were similar to each other, but lower than the Ozarks, and the Delta region contributed the least, but with a generally stable harvest

Sixth annual conference on alaskan placer mining

An abridged format of papers, presentations and addresses given during the 1984 conference held on March 28-29, 1984, compiled and edited by Daniel E. Walsh and M. Susan Wray

Management Options for the Inland Fisheries Resource in South Sumatra, Indonesia: I Bioeconomic Model

The inland fishery in South Sumatra, Indonesia, is an important source of income, employment and protein to small-scale fishers. Some overall indicators, such as virtual disappearance of certain important species and continuous reduction in the size of harvested fish, indicate that the fishery is not being exploited on a sustainable basis. In this study, an evaluation of the status of the existing fish stock is undertaken, and an analytical model for identifying efficient levels of exploitation of the fishery is developed. Primary data are used to describe the current costs of fishing effort. Secondary data, combined with results of analysis of primary data, are then used to derive a supply function for the fishery. Different types of fishing gear are standardised into a single type of fishing unit, and mixed species of harvested fish are treated as an aggregated fish stock. Empirical results reveal that both riverine and swamp fisheries in South Sumatra were biologically and economically over-fished during the period of study. This implies that regulation is required to reduce the level of fishing effort.smallholder fisheries, bioeconomic analysis, Inland fisheries, Indonesia, Sumatra, Resource /Energy Economics and Policy,

Investigation of taste tainting in salmon flesh in the Ribble catchment

This report presents the findings of the first phase of an investigation into the cause(s) of taints in salmonid fish in the River Ribble, commissioned by the North West Region of the Environment Agency. There have been reports of tainting in fish taken from both the estuary and the freshwater river for many years, but the contaminants involved and their source and transport pathway are unknown. Tainting by phenols has been of specific concern in the past. The work programme comprised: examination of tainting reports; collection of salmonids; their submission for taste testing; literature review; analysis of fish flesh using gas chromatography-mass spectrometry (GCMS) and analysis of river bed sediments. From enquiries, three common descriptors of the 'taint' were identified: disinfectanty; diesely; and muddy. The incidence of taints appears transient/irregular and may therefore relate to the incidence of discharges and specific threshold concentrations of pollutants. The literature review showed that a wide range of organic compounds including many industrial chemicals, and others which are naturally occurring, can taint fish flesh. Taste testing confirmed the presence of tainted salmon and trout in the Ribbie Catchment. It identified a low incidence of 'untainted' fish but demonstrated the 'taint' to be not specific to one tainting substance. Differences were found both between the species and fish from different parts of the catchment. Overall, most fish exhibited an unpleasant flavour, though this may have been influenced to some extent by the fact that most were sexually mature. The worst tainting was found in trout from the river Calder: a soapy/chemical aftertaste. An unpleasant earthy/musty flavour distinguished the salmon from the trout. Phenol was shown to have been a minor issue during the present study, whilst no hydrocarbon taints were identified. Examination of tissue from the eight salmon exhibiting the worst taints revealed the presence of aromatic hydrocarbons, but no phenolic compounds. Other notable substances present in the fish were siioxanes and benzophenone. Data from sediment analysis is presented which shows the main compounds present to be aromatic and polyaromatic hydrocarbons, that concentrations at two locations R. Darwen and R. Calder were significantly higher than at other sites, and that some phenolic compounds were detected at low levels. A paucity of fish flesh taste descriptors linked to specific compounds prevented an obvious correlation to be made between the tastes observed and the organic compounds detected. Descriptors frequently used by the taste testing panel (e.g. earthy, musty, astringency, chemical) cannot be linked to any of the compounds identified in the tissue analyses. No taste information was available from the literature on siioxanes. Aromatic hydrocarbons though present in tissue and sediments were not identified as tainting

Socioeconomic factors that affect artisanal fishers’ readiness to exit a declining fishery

The emerging world crisis created by declining fish stocks poses a challenge to resource users and managers. The problem is particularly acute in poor nations, such as those in East Africa, where fishing is an important subsistence activity but high fishing intensity and use of destructive gear have resulted in declining catches. In this context developing effective management strategies requires an understanding of how fishers may respond to declines in catch. We examined the readiness of 141 Kenyan fishers to stop fishing under hypothetical scenarios of declines in catch and how socioeconomic conditions influenced their decisions. As expected, the proportion of fishers that would exit the fishery increased with magnitude of decline in catch. Fishers were more likely to say they would stop fishing if they were from households that had a higher material style of life and a greater number of occupations. Variables such as capital investment in the fishery and the proportion of catch sold had weak, nonsignificant relationships. Our finding that fishers from poorer households would be less likely to exit a severely declining fishery is consistent with the literature on poverty traps, which suggests the poor are unable to mobilize the necessary resources to overcome either shocks or chronic low-income situations and consequently may remain in poverty. This finding supports the proposition \ud that wealth generation and employment opportunities directed at the poorest fishers may help reduce fishing effort on overexploited fisheries, but successful interventions such as these will require an understanding of the socioeconomic context in which fishers operate. \u