BIOCHEMICAL TOOLS AS INDICATORS OF FISH STOCK RECOVERY FOLLOWING OIL EXPOSURE

1997 ◽  
Vol 1997 (1) ◽  
pp. 1023-1023
Author(s):  
M. M. Gagnon
2019 ◽  
Author(s):  
Oceana ◽  
Louise Teh ◽  
Rashid Sumaila

Many fish populations in Canada are depleted and at risk of further decline. Fisheries loss jeopardizes the social, economic, and health well-being of thousands of Canadians and is therefore of national concern. However, of 56 fish stocks assessed as being in a Critical or Cautious state, only three have rebuilding plans developed for them. As such, there is an urgent need to intensify Canada’s fisheries rebuilding efforts. One of the challenges facing rebuilding fisheries is that it often necessitates an immediate and substantial reduction in fishing mortality. This invariably involves forgoing certain short-term benefits in order to gain the benefits of rebuilt fish stocks in the medium and long term. To investigate the economic and social implications of rebuilding Canada’s fisheries, this study analyzes the socio-economic costs and benefits of rebuilding Canada’s fisheries under six different scenarios of species’ recovery rates and management strategies. We conduct the analysis for six fish stocks representing different biological life histories, geographic distribution, state of fisheries depletion, and socio-economic importance to coastal communities. These fish stocks include: i) Pacific herring Central Coast stock; ii) West Coast Vancouver Island chinook salmon — both aggregate abundance-based management (AABM) and individual stock-based management (ISBM) components; iii) yelloweye rockfish outside population; iv) Atlantic cod NAFO Division 2J3KL; v) Gulf of St. Lawrence Atlantic herring spring spawners NAFO Division 4T; and vi) Atlantic redfish Units 1 and 2.Our results indicate that overall, for the time period studied, all fish stocks — except yelloweye rockfish, which is a long-lived species with a low natural growth rate — would likely experience economic gains from fisheries rebuilding relative to the status quo. Under the most optimistic scenario, northern cod (which has, among the fisheries studied, one of the largest current catch and number of fishers) and Pacific herring are projected to benefit the most by the end of the analysis period, with potential economic gains of seven and 11 times above the status quo, respectively. Under the least optimistic scenario, this gain drops to 0.85 and five times above the status quo, respectively. In most cases, a management strategy involving fishery closure results in higher potential economic gains compared to a low-fishing strategy, regardless of the rate of fish-stock recovery. Not surprisingly, slow recovery scenarios are projected to result in the fewest economic gains. An intergenerational discounting approach, which seeks to explicitly incorporate the interests of future generations in the analysis, increases projected economic benefits compared to conventional discounting, thereby emphasizing the importance of taking a long-term perspective to fisheries rebuilding. Using fish stock assessments as a basis, we estimate that once fish stocks are rebuilt, they can support catches that range from 1.3 to 18 times above the status quo catch level. In terms of social impact, an estimated 5,100 fishers are currently involved in fisheries for the case study fish stocks, who can thus potentially benefit from this projected increase in fish catch in the future. The overall benefits of rebuilding are magnified if we consider the thousands more people in coastal communities who have food, cultural, and other social connections to fish stocks. While rebuilding may likely incur short-term costs for fishers and coastal communities, these need to be seen in light of the fact that without rebuilding and effective fisheries management, we have lost significant amounts of food, jobs, and incomes over the recent decades, and we could lose everything if and when the fish stocks collapse. Recall the cost to fishers and society when the cod stocks off Newfoundland collapsed in 1992.Our results suggest that bearing this short-term cost can lead to economic benefits, which in the long term are an improvement over maintaining the status quo. This suggests that accounting for social impacts is crucial in developing rebuilding plans, especially in terms of access to and allocation of projected economic benefits from rebuilt fish stocks in the future. This study further highlights that rebuilding plans have to be developed while bearing in mind that anticipated fish stock recovery can either be delayed or sped up by future changes in environmental conditions, which, although not modelled here, can change projected economic outcomes. While we show that fisheries rebuilding can improve the biological and economic state of Canadian fish stocks overall, it is also important to emphasize the need for Canada to have strong precautionary fisheries management practices in place for species that are not currently depleted so that fish stocks are managed sustainably, avoiding the need for rebuilding.


Author(s):  
Masako Yamada ◽  
Yutaka Tanuma

Although many fine structural studies on the vertebrate liver have been reported on mammals, avians, reptiles, amphibians, teleosts and cyclostomes, there are no studies on elasmobranchii liver except one by T. Ito etal. (1962) who studied it on light microscopic level. The purpose of the present study was to as certain the ultrastructural details and cytochemical characteristics of normal elasmobranchii liver and was to compare with the other higher vertebrate ones.Seventeen Scyliorhinus torazame, one kind of elasmobranchii, were obtained from the fish stock of the Ueno Zoo aquarium, Ueno, Tokyo. The sharks weighing about 300-600g were anesthetized with MS-222 (Sigma), and the livers were fixed by perfusion fixation via the portal vein according to the procedure of Y. Saito et al. (1980) for 10 min. Then the liver tissues were immersed in the same fixative for 2 hours and postfixed with 1% OsO4-solution in 0.1 Mc acodylate buffer for one hour. In order to make sure a phagocytic activity of Kupffer cells, latex particles (0.8 μm in diameter, 0.05mg/100 g b.w.) were injected through the portal vein for one min before fixation. For preservation of lipid droplets in the cytoplasm, a series of these procedure were performed under ice cold temperature until the end of dehydration.


Author(s):  
Vincentius P. Siregar ◽  
Sam Wouthuyzen ◽  
Andriani Sunuddin ◽  
Ari Anggoro ◽  
Ade Ayu Mustika

Shallow marine waters comprise diverse benthic types forming habitats for reef fish community, which important for the livelihood of coastal and small island inhabitants. Satellite imagery provide synoptic map of benthic habitat and further utilized to estimate reef fish stock. The objective of this research was to estimate reef fish stock in complex coral reef of Pulau Pari, by utilizing high resolution satellite imagery of the WorldView-2 in combination with field data such as visual census of reef fish. Field survey was conducted between May-August 2013 with 160 sampling points representing four sites (north, south, west, and east). The image was analy-zed and grouped into five classes of benthic habitats i.e., live coral (LC), dead coral (DC), sand (Sa), seagrass (Sg), and mix (Mx) (combination seagrass+coral and seagrass+sand). The overall accuracy of benthic habitat map was 78%. Field survey revealed that the highest live coral cover (58%) was found at the north site with fish density 3.69 and 1.50 ind/m2at 3 and 10 m depth, respectively. Meanwhile, the lowest live coral cover (18%) was found at the south site with fish density 2.79 and 2.18  ind/m2 at 3 and 10 m depth, respectively. Interpolation on fish density data in each habitat class resulted in standing stock reef fish estimation:  LC (5,340,698 ind), DC (56,254,356 ind), Sa (13,370,154 ind), Sg (1,776,195 ind) and Mx (14,557,680 ind). Keywords: mapping, satellite imagery, benthic habitat, reef fish, stock estimation


1995 ◽  
Vol 32 (4) ◽  
pp. 187-196 ◽  
Author(s):  
L. Pechar

The study presents data on the species composition of cyanobacterial water blooms in Czech fish ponds from the 1950s to the 1990s. Since the 1950s, a shift from large-colonial Aphanizomenon flos-aquae var. flos-aquae through Microcystis aeruginosa and small-colonial species of Anabaena to single-filament species (Planktohrix agardhii, Limnothrix redekei, Aphanizomenon gracile) or single-cell forms (Microcystis ichtyoblabe), has been observed. The changes in the species composition of the water blooms are closely related to changes in fishery management (increase in fish stock, increase in application of organic fertilizers). At present the high predation of fish upon zooplankton results in elimination of large colonial blooms of A. flos-aquae associated with large filtering zooplankton (Daphnia). Low grazing pressure of zooplankton, low light conditions and low N:P ratios are suitable conditions for mass development of the small species of cyanobacteria. High pH is not necessary to achieve cyanobacteria dominance.


1995 ◽  
Vol 31 (8) ◽  
pp. 239-243 ◽  
Author(s):  
W. Ligtvoet ◽  
S. A. de Jong

In the 6000 ha Lake Volkerak-Zoom, a new freshwater system in the estuarine southwest of The Netherlands, biomanipulation is used as a tool in ecosystem development. The basic ecological concepts for ecosystem development are described. Key factors in the integrated water management are fish stock management and water level management, geared towards creating optimal conditions for northern pike, the dominant predator in mesotrophic waters. The main aspects of the water level management and the fish stock management are outlined.


2001 ◽  
Vol 58 (11) ◽  
pp. 2139-2148 ◽  
Author(s):  
D G Chen

A fuzzy logic approach is developed to model and test the impact of environmental regimes on fish stock–recruitment relationships. Traditional methods use environmental variables to classify stock–recruitment data into different membership percentiles followed by fitting the stock–recruitment models for each subset. In contrast, the fuzzy logic approach uses a continuous membership function to provide a rational basis for the classification. Thus, parameter estimation is based on a more logically consistent foundation without resorting to subjective partitions. This new approach is applied to herring stock from the west coast of Vancouver Island (Clupea harengus pallasi) using sea surface temperature as the environmental variable and to Pacific halibut stock (Hippoglossus stenolepis) using the Pacific Decadal Oscillation as the environmental variable. From these applications, the herring stock–recruitment relationships were found to vary significantly during different regimes, whereas this was not the case for halibut. However, in both instances, the fuzzy logic approach demonstrated that density-dependent effects differed between regimes. The fuzzy logic model consistently outperformed traditional approaches as measured by several diagnostic criteria. Because fuzzy logic models address uncertainty better than traditional approaches, they have the potential to improve our ability to understand factors influencing stock–recruitment relationships and thereby manage fisheries more effectively.


2014 ◽  
Vol 79 (1-2) ◽  
pp. 87-93 ◽  
Author(s):  
Ahmad Omar Ali ◽  
Claudia Hohn ◽  
Peter J. Allen ◽  
Lorelei Ford ◽  
Mary Beth Dail ◽  
...  

2002 ◽  
Vol 60 (4) ◽  
pp. 838-856 ◽  
Author(s):  
P. C. Goudswaard ◽  
F. Witte ◽  
E. F. B. Katunzi

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