Fishing

About: Fishing is a research topic. Over the lifetime, 26543 publications have been published within this topic receiving 455552 citations. The topic is also known as: angling.

Maintenance and recovery of reef fishery productivity

Abstract: Non-conventional methods to maintain and restore reef fishery productivity include protecting fishery habitats, hatchery releases, artificial reefs, introduction of exotic species, habitat restoration and marine fishery reserves. I conclude that it is far better to prevent overfishing and stock collapse in the first place than to have to rebuild fishery productivity later. The most important strategies to prevent loss of fishery productivity are switching to less destructive fishing methods, preventing destruction of fishery habitats and protecting some areas by establishment of marine fishery reserves. If fisheries must be rebuilt, habitat restoration and marine reserves appear to be the more promising alternatives over the long term. Except for unique circumstances, deployment of artificial reefs and release of hatchery-raised organisms have less potential for retrieving lost fishery productivity. Because of unpredictable consequences and the general inability to correct mistakes, the introduction of exotic organisms is the least favoured alternative for rebuilding fishery productivity.

Climate, Anchovy, and Sardine.

Abstract: Anchovy and sardine populated productive ocean regions over hundreds of thousands of years under a naturally varying climate, and are now subject to climate change of equal or greater magnitude occurring over decades to centuries. We hypothesize that anchovy and sardine populations are limited in size by the supply of nitrogen from outside their habitats originating from upwelling, mixing, and rivers. Projections of the responses of anchovy and sardine to climate change rely on a range of model types and consideration of the effects of climate on lower trophic levels, the effects of fishing on higher trophic levels, and the traits of these two types of fish. Distribution, phenology, nutrient supply, plankton composition and production, habitat compression, fishing, and acclimation and adaptation may be affected by ocean warming, acidification, deoxygenation, and altered hydrology. Observations of populations and evaluation of model skill are essential to resolve the effects of climate change on these fish.

Marine reserves: patterns of adult movement of the coral trout (Plectropomus leopardus (Serranidae))

Abstract: Movements of Plectropomus leopardus (Serranidae), a major fisheries species, across marine reserve boundaries were investigated on the Great Barrier Reef, Australia. Mark-release-recapture and ultrasonic telemetry were used to assess movements. Mark-release-recapture used hook and line as the method of capture and underwater visual census (UVC) as the "recapture" tool. Catch rates were significantly higher in zones closed to fishing, despite UVC indicating no significant differences in density between closed and open zones. Of 183 fish marked with numerical freeze brands, 93 estimates of movements of branded fish were obtained. No branded fish was recorded to cross the reserve boundaries during the 2-month study, probably due to the initial decision to allocate capture effort evenly across the study area, rather than concentrating it on reserve boundaries. Fish carrying ultrasonic transmitters, and having home ranges straddling reserve boundaries, crossed boundaries on average 15.3 times•month⁻¹. The mean distance moved by freeze branded specimens between capture and recapture was significantly larger in areas closed to fishing than in those open to fishing. However, mean distance moved per day determined by ultrasonic telemetry did not differ between areas closed and open to fishing. This study suggests low flux rates of adult P. leopardus across marine reserve boundaries.

Modelling an exploited marine fish community with 15 parameters - results from a simple size-based model

Abstract: To measure and predict the response of fish communities to exploitation, it is necessary to understand how the direct and indirect effects of fishing interact. Because fishing and predation are size-selective processes, the potential response can be explored with size-based models. We use a simulation approach to describe the relationship between size spectrum slope and overall fishing mortality and to try to understand how a linear spectrum might be maintained. The model uses 15 parameters to describe a 13-‘‘species’’ fish community, where species are defined by their maximum body size and the general relationship between size and life-history characteristics. The simulations allow us to assess the role of changes in the strength and type of density dependence in controlling the response to fishing, and to investigate the trade-off between catches and stock status of the different species. The outputs showed that the linear slope of the size spectrum was a function of community exploitation rate. Density-dependent controls, specifically predation mortality and the extent of compensation in the stock-recruit relationship, were key mechanisms in maintaining a linear spectrum. A linear spectrum emerged independent of the rate of compensation in the stockrecruit relationship. When this rate was low, the effects of changes in fishing mortality on predator abundance dominated those on spawning-stock biomass, whereas the dominance was reversed when the compensation rate in the stock-recruit relationship was high. The approach allows us to explore the effects of different fishing mortality schedules on properties of the fish community, to assess how fishing affects species with different life histories in mixed fisheries, and to assess the effects of selectively fishing different size classes. The simulations indicate that the size classes to be included when developing and interpreting size-based metrics must be carefully considered in relation to the trophic structure and likely strength of predatory interactions in the community. Runs with different fishing mortality by size suggest that the dynamics of predation cannot compensate fully for changing rates and patterns of exploitation, implying that the effects of selectively fishing different size classes should be assessed on a case-by-case basis.