Fishery Discards: Factors Affecting Their Variability within a Demersal Trawl Fishery

Discards represent one of the most important issues within current commercial fishing. It occurs for a range of reasons and is influenced by an even more complex array of factors. We address this issue by examining the data collected within the Danish discard observer program and describe the factors that influence discarding within the Danish Kattegat demersal fleet over the period 1997 to 2008. Generalised additive models were used to assess how discards of the 3 main target species, Norway lobster, cod and plaice, and their subcomponents (under and over minimum landings size) are influenced by important factors and their potential relevance to management. Our results show that discards are influenced by a range of different factors that are different for each species and portion of discards. We argue that knowledge about the factors influential to discarding and their use in relation to potential mitigation measures are essential for future fisheries management strategies

Fructan and its relationship to abiotic stress tolerance in plants

Numerous studies have been published that attempted to correlate fructan concentrations with freezing and drought tolerance. Studies investigating the effect of fructan on liposomes indicated that a direct interaction between membranes and fructan was possible. This new area of research began to move fructan and its association with stress beyond mere correlation by confirming that fructan has the capacity to stabilize membranes during drying by inserting at least part of the polysaccharide into the lipid headgroup region of the membrane. This helps prevent leakage when water is removed from the system either during freezing or drought. When plants were transformed with the ability to synthesize fructan, a concomitant increase in drought and/or freezing tolerance was confirmed. These experiments indicate that besides an indirect effect of supplying tissues with hexose sugars, fructan has a direct protective effect that can be demonstrated by both model systems and genetic transformation

The survival of skates (Rajidae) caught by demersal trawlers fishing in UK waters

Skates and rays are a common component of mixed demersal fisheries, and large quantities may be discarded. Given their biological vulnerability, understanding the fate of these elasmobranchs is of management concern. Estimates of discard survival are needed for modelling the possible benefits of management measures. In this study, the focus is on the Bristol Channel skate fishery, where on-board holding tanks were used to assess the short-term rates of survival of trawl-caught skates (Rajidae). From monitoring the survival rates of 162 fish kept in specially designed on-board holding tanks for periods of up to 72 h, the short-term rate of survival was 55%. Visual inspection of "health" at time zero was a good indicator of survival, because 79% of skates with a poor health score did not survive. Mortality rates for fish of moderate health and good "health" were 16% and 5%, respectively. This information allows one to predict the consequences of fishing practice on discard survival using a larger dataset on fish scored for health before tagging and release. The proportion in poor condition on capture is positively correlated with estimated codend weight, so technical modifications to fishing gear aimed at reducing unwanted by-catch would increase the survival of discarded skates. Combined with information on discarding rates in the study area, the results indicate that discard mortality removes almost as many fish from the skate stock as are landed commercially