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The combination of increasing atmospheric depositions of reactive nitrogen (N) and the highly effective diminishing of external phosphorus (P) loadings can change key nutrient ratios in lake ecosystems. Consequently, ratios of dissolved inorganic N (DIN) to dissolved P (DP) in lakes are increasing. However, potential consequences for aquatic organisms are as yet far from understood.We formulated three hypotheses on the potential effects of rising DIN:DP ratios on a lake food web: (1) increasing DIN:DP ratios intensify the P limitation of phytoplankton communities and lower their food quality; (2) densities of P rich zooplankters (e.g. cladocerans) will be negatively affected by P‐limited food algae; (3) as result, planktivorous fish will experience a reduction of their main prey (especially Daphnia species) and respond with lowered growth.These hypotheses were tested in a mesocosm experiment conducted in a pre‐alpine lake in southern Germany, Lake Brunnensee. For 76 days, the natural phytoplankton and zooplankton communities were exposed to a wide gradient of DIN:DP ratios. At the end of the experiment, juvenile planktivorous whitefish (Coregonus macrophthalmus) were released into the mesocosms and allowed to feed on zooplankton communities for 72 hr.Along the gradient of DIN:DP ratios, we found evidence for a rising P limitation of autotroph growth, which was indicated by increasing ratios of N:P (15:1–157:1) and C:P (91:1–797:1) in seston biomass. The rising P limitation in algae reduced the nutritional food quality for the majority of herbivorous zooplankton. Both the total zooplankton biomass and the Daphnia biomass declined substantially with increasing DIN:DP ratios. In contrast, increasing DIN:DP ratios favoured rotifer species, showing strong positive correlation with rotifer biomass. Whitefish weights decreased with increasing rotifer biomass and increased with rising Daphnia biomass in zooplankton communities.In summary, our results provide an experimental demonstration that increasing DIN:DP ratios can cause stoichiometric shifts in the biomass of primary producers towards higher N:P and C:P ratios. Effects on zooplankton were changes in the taxonomical community composition towards lower cladoceran biomass (mainly Daphnia spp.). The reduction in Daphnia biomass in turn caused significantly reduced growth rates of whitefish in our experiment. Our experimental results therefore support the assumption that stoichiometric effects can travel up the food chain. General consequences of such multi‐trophic effects induced by altered nutrient ratios could be potentially visible during re‐oligotrophication of water bodies, often resulting in high N:P ratios. Further empirical studies could look for signatures of these effects on the yield of economically important species. [ABSTRACT FROM AUTHOR]

Transcriptomic studies are facilitating the search for the molecular bases of adaptation in natural populations, but the impact of these differences in mRNA content on animal physiology are often unknown. One way to determine if molecular changes have the potential to influence animal physiology and performance is to test for correlated changes at higher levels of biological organization, including enzyme activity. Here, we measure the activities of carbohydrate metabolism enzymes to test if previously documented genetic and transcriptomic variation between ‘dwarf’ and ‘normal’ Lake Whitefish ecotypes are associated with corresponding changes in enzyme activity (measured as maximal rate, V max ) in liver and skeletal muscle. We use laboratory-reared fish from the same populations as prior transcriptomic studies and find that white muscle mRNA content is a good predictor of glycolytic and glycogen metabolism enzyme activity, and dwarf whitefish have evolved higher activities than normal whitefish. However, the differences in hepatic mRNA content found between ecotypes in prior studies are not associated with comparable changes in enzyme activity. For example, dwarf whitefish have lower enzyme activities, but higher transcript abundances for two glycolytic enzymes compared to normal whitefish. Overall, we find that transcriptomic studies successfully highlight evolutionary variation in enzyme activities, but not always in the direction predicted, indicating that a variety of tissue-specific regulatory mechanisms contributed to the evolution of energy metabolism in Lake Whitefish. [ABSTRACT FROM AUTHOR]

Abstract: We estimated the effect of the gill‐net fisheries targeted at whitefish (Coregonus sp.) on anadromous sea trout, Salmo trutta, in the Gulf of Bothnia, Baltic Sea using separate data for fish species. The analysis of sea trout captures was based on tagging and recapture data collected in 1998–2011, while whitefish data were derived from individual samples of commercial fisheries from the same period. The mesh sizes used in gill‐net fishing and the seasonal and temporal distributions of recaptured sea trout and sampled whitefish were compared in the northern and southern Gulf of Bothnia. The trout had typically spent 1–2 years at sea, and they were mainly immature with a median body length of 40–43 cm at the time of recapture in gill nets. Despite the increase in the minimum permitted landing size from 40 to 50 cm in 2008, the median length of recaptured trout remained unchanged during the study period. Most (59%) of the gillnetted trout were caught in the southern Gulf of Bothnia in gill nets with mesh sizes of 40–45 mm, which were also used in the whitefish fishery (72%). In the northern Gulf of Bothnia, nets with a smaller mesh size of 25–39 mm took 83% of the whitefish catch and 39% from recaptured trout. In both areas, the overlap in mesh sizes used to gill‐net catch whitefish and sea trout increased during the study period. There were clear seasonal and areal differences in the relative probability of sea trout being captured in gill nets, suggesting that carefully tailored spatial and temporal restrictions on gill‐net fisheries could provide a tool to protect young sea trout without causing intolerable difficulties for the fisheries targeting other species. [ABSTRACT FROM AUTHOR]

Abstract: The size of anadromous whitefish caught with dip nets in the River Tornionjoki in the northern part of the Gulf of Bothnia has decreased during recent decades. To find an explanation for this trend, ascending whitefish were sampled in the lower part of the river in August 2016, and they were divided into two groups according to fish length. The length of the SMALL group was ≤ 32 cm (n = 32) and that of the LARGE group ≥ 33 cm (n = 65). The elemental analysis of otoliths revealed that the barium concentration was clearly higher in otoliths from the SMALL group compared to the LARGE group. This indicates that the fish in the LARGE group had migrated to feed further south in the Gulf of Bothnia, with a higher salinity, than the fish in the SMALL group. Because of this migration difference, and a decline in the gillnet effort, especially in the feeding areas near the river mouth, it is assumed that proportionally more fish in the SMALL group are able to ascend the river to spawn than previously, thus decreasing the mean size. At the same time, the heavy gillnet fishery in the south removes fish from the LARGE group. [ABSTRACT FROM AUTHOR]

Identification of ecologically mediated mechanisms that drive population dynamical changes in fish communities and polymorphic fish stocks such as those of whitefish, Coregonus lavaretus , requires data that are seldom available in freshwater systems. We assessed the stock of each morphologically distinguishable whitefish form (native lesser sparsely-rakered whitefish, native blue whitefish and stocked northern densely-rakered whitefish) in the Lake Oulujärvi during 1973–2014, and related temporal variations in population dynamics to environmental data and catch per unit of effort (CPUE) data on other species having fisheries significance. The results demonstrated a synchronous major decline in the abundance of the native whitefish forms and a decline in the length-at-age of all forms. During the study period, summer time water temperature increased and surface water phosphorous concentration decreased. Recruitment in all whitefish forms showed Ricker-type dependence on spawning stock biomass but little residual correlation with the environmental parameters. Cross-correlation analyses suggested that the re-establishment of pikeperch Sander lucioperca population affected negatively both the recruitment and biomass of whitefish but the exact effect mechanisms require further assessment. Our results exemplify that ecosystem-based fisheries management in inland waters must take into account both natural and human-induced environmental changes as well as stockings, and that knowledge-based inland fisheries management is inherently data-intensive. [ABSTRACT FROM AUTHOR]

Fish are often externally tagged to determine the abundance, exploitation rates, and other key aspects of their ecology. Tag retention rates, however, may vary by tag type. The main objective of this study was to determine the retention rates of three external tags (Atkins, dart, and opercular tags) implanted onto White-streaked GroupersEpinephelus ongusin their natural habitat. White-streaked Groupers were tagged with different external tags, along with a plastic-infusion-process PIT (PIP PIT) tag, and retention rates were evaluated in experimental tanks for 54 weeks and in their natural habitat for 374 d. None of the fish kept in experimental tanks shed their abdominally implanted PIP PIT tags over 54 weeks. The mean retention rates of the external Atkins, dart, and opercular tags were considerably lower under natural conditions (16.7 ± 2.8%, 37.5 ± 3.3%, and 28.6 ± 3.4%, respectively) than in the laboratory (80%, 70%, and 70%, respectively). Loss of tags under natural conditions may have resulted from snagging on complex structures in their habitats and on interspecies interactions. Received February 23, 2015; accepted October 27, 2015 [ABSTRACT FROM PUBLISHER]

In this study, we are concern with incorporating risk factors into the Almost Ideal Demand System model. In the modified model, the risk factors affect trade response to price changes (the indirect effect) and the reallocation of the import expenditure (the direct effect). This specification can be used to explain why the trade effect of risk factors is ambiguous regarding the magnitude and sign. The empirical application to the US whitefish import market reveals the proportionality between the risk and the price effects and further implies a general positive direct effect. [ABSTRACT FROM AUTHOR]

We evaluated the diet of Lake WhitefishCoregonus clupeaformisin Lake Huron during 2002–2011 to determine the importance of Round GobyNeogobius melanostomusand other fish as prey items. Lake Whitefish that had reached approximately 400 mm in length incorporated fish into their diets. The overall percentage of adult Lake Whitefish in Lake Huron that had eaten fish increased from 10% in 2002–2006 to 20% in 2007–2011, with a corresponding decrease in the frequency of Lake Whitefish that ateDreissenaspp. from 52% to 33%. During 2002–2006, Round Goby (wet mass, 38%), sculpins (Cottidae) (34%), and Ninespine SticklebackPungitius pungitius(18%) were the primary fish eaten, whereas Round Goby accounted for 92% of the fish eaten in 2007–2011. Overall, Round Goby were found in the fewest Lake Whitefish stomachs in the north region of Lake Huron (6%) and in the most in the central (23%) and south (19%) regions of the lake. In the central region, Round Goby were eaten during all seasons that were sampled (spring through fall). In the south region, Round Goby were eaten only in the winter and spring but not in the summer whenDreissenaspp. and spiny water fleaBythotrephes longimanusdominated the diet. Based on the 2007–2011 diet composition, an individual Lake Whitefish would need to have increased their consumption relative to that in 1983–1994 by 6% in the north region, 12% in the central region, and 41% in the southern region in order to achieve the same growth that was observed before dreissenid mussels arrived. However, Lake Whitefish weight adjusted for length only increased by 2% between 2002–2006 and 2007–2011 in the central region, decreased by 4% in the northern region, and remained constant in the southern region. This suggests that a shift toward more frequent piscivory does not necessarily improve the condition of a generalist feeder like Lake Whitefish. Received June 14, 2013; accepted August 28, 2013 [ABSTRACT FROM AUTHOR]

The history of fisheries exploitation in Canada has significant ties to the development and westward expansion of the fur trade. Understanding the scale and nature of this relationship is important when assessing the developmental or evolutionary history of a system. This study uses estimates of human population size and subsistence lake whitefish (Coregonus clupeaformis) consumption to estimate annual fish harvest at Lac la Biche, Alberta (54°52'N, 112°05'W) during the fur trade era and to assess the magnitude and potential influence ofhistoric harvest on contemporary harvest potential. Historic (1800-1911) lake whitefish harvest increased approximately 10-fold, from 74,000kg in 1800 to 811,000kg in 1875, immediatelypreceding a lake whitefish population collapse in 1878. Following the initiation of a formal commercial fishing industry, contemporary (1912-2009) harvest peaked at 424,000 kg, about one half the previous estimated maximum. The persistence of/ow contemporary harvest bio- masses suggests a shift from a system of high- to low-lake whitefish productivity, likely resulting from decreasing ecosystem resilience with increasing harvest pressure. Knowledge of historic fish harvest can minimize the impacts of the shifting baseline syndrome by elucidating the magnitude and impacts of historic harvests on future harvest potential and potential production. [ABSTRACT FROM AUTHOR]

Abstract: Comparative trials were carried out to evaluate the performance of the GOV (Grande Ouverture Verticale) survey trawl in relation to a commercial whitefish trawl. The gears were rigged in a twin trawl configuration and a comparison of catch rates suggest that, overall, the differences in performance between the two gears are not great, and vary depending on species and whether the commercial gear is fished with or without a tickler chain. There was no difference in relative catch rate for cod (Gadus morhua) between the commercial gear without a tickler chain and the GOV. However, the commercial gear caught fewer small haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus) and more larger ones; fewer lemon sole (Microstomus kitt) and more plaice (Pleuronectes platessa) of all sizes. The addition of a tickler chain to the commercial gear significantly increased the catch rate of cod (particularly smaller ones), lemon sole and plaice; but had no significant effect on haddock or whiting. Smaller number of other species were also caught and a comparison of catch weights suggests that there is no difference for saithe (Pollachius virens) and hake (Merluccius merluccius), while the commercial net was better for megrim (Lepidorhombus whiffiagonis) and monkfish (Lophius piscatorius). [Copyright &y& Elsevier]

Abstract: Few studies have evaluated the performance of harvest control rules while considering uncertainties in life history traits and the management process. We conducted such a study using an age-structured simulation based on lake whitefish in the Great Lakes. The control rules compared were a constant fishing mortality (constantF), conditional constant catch (CCC), biomass-based (BB), and constantF and BB with a 15% limit on the interannual change in the target catch (constantF-lim, BB-lim, respectively). Our application of the CCC and BB rules was conditioned on having reliable estimates of some reference point (e.g., unfished biomass). With appropriate policy parameters, the BB and constantF rules attained higher average yield and spawning stock biomass than other control rules. At yields that could be achieved by all rules, the CCC, constantF-lim, and BB-lim rules had the lowest yearly variability in yield, but at the cost of more frequent low biomass. The relative performance of the control rules was generally consistent with previous research that did not include the variation in life history traits unique to our simulations, which suggested that these variable traits did not affect relative control rule performance. The BB rule achieved more yield and less risk of low biomass than the constantF rule currently used for lake whitefish, with only a modest increase in yield variability. Given that the BB rule requires a stock-specific estimate of unfished biomass, and the constantF rule does not, this result suggests that reliable estimates of unfished biomass could provide substantial value. [Copyright &y& Elsevier]

Abstract: Competition between seals and man for valuable fish resources is a long-standing contentious issue and of concern with fish stocks in global decline. Estimating resource overlap between seals and fisheries is difficult and generally achieved by comparing seal consumption with fisheries catches and stock size; however spatial partitioning may mean that marine mammals and fisheries are not actually depleting the same local stocks. With the relatively recent availability of fine scale fishing effort data from Vessel Monitoring System (VMS) it is now possible to study the spatial overlap between fisheries and predators in more detail. We used VMS and fast acquisition GPS to compare the distribution of fisheries and seals in Irish waters on the same spatial and temporal scales to quantify overlap. Our findings suggest a significantly low rate of spatial overlap between a sample of female grey seals (Halichoerus grypus) and the offshore whitefish fishery on the Irish continental shelf, suggesting direct competition for the resource may be far less than expected, if the sample is representative. Seal/fisheries interactions in Irish waters could therefore be more of an issue at the operational and individual level suggesting population control measures such as culling will be ineffective and therefore unjustifiable. The approach could be applied elsewhere to examine spatial overlap of humans and key marine species such as turtles, seals and seabirds, providing critical data for the development of mitigation measures which will ultimately contribute to the conservation of these species, many of which are fundamental for healthy ecosystem functioning. [Copyright &y& Elsevier]

Lake whitefishCoregonus clupeaformiswere commercially fished in Lake Champlain until the 1913 fishery closure in U.S. waters. The only study of lake whitefish in the lake had been done in the 1930s. Our goals were to compare current biological parameters with historical information and to determine distribution and spatial differences in larval densities, with an emphasis on locating current spawning grounds, to gain insight on the current population in Lake Champlain. Adult lake whitefish (N= 545) were collected from 2006 to 2010 by using gill nets and trawls focused in the Main Lake. Larvae were collected extensively lakewide and intensively at Wilcox Cove and Rockwell Bay with an ichthyoplankton net. Population attributes (size, age, and sex composition; and growth, condition, and mortality) were typical of unexploited populations, as there was a wide range of length-classes (126–638 mm total length) and age-classes (1–26 years). Lake whitefish from the Main Lake had a high condition factor, and growth parameters were comparable with those of fish collected in the 1930s. Lake Champlain lake whitefish had greater asymptotic lengths than generally documented for the species. Larvae were found at sites throughout the Main Lake, and larval densities were among the highest recorded for the species (maximum = 2,558 larvae/1,000 m3); however, no lake whitefish were collected on the two historically documented spawning grounds. Lake whitefish in the Main Lake demonstrate characteristics of an unexploited population; however, evidence of spawning is absent or rare in portions of their historic range where habitat has been altered. Received February 22, 2011; accepted August 24, 2011 [ABSTRACT FROM PUBLISHER]

Abstract: The Irish otter trawl fleet operates in a complex multi-species multi-gear fishery, spanning a wide geographic area, and involving around 275 trawlers. Factorial and clustering methods were applied to 2003 fishing trip data to define thirty-three métiers. Definitions were based on six trip characteristics taken from logbooks, namely: fishing gear, mesh size, vessel length, species composition, area, and month. Métiers exploiting demersal species or species groups are characterised by single vessel bottom otter trawls, typically with mesh sizes of 70mm or more, operating year round. This includes nine Nephrops dominated métiers highlighting the importance of this species to the fleet. Many demersal métiers are characterised by groups of species, such as mixed whitefish or slope species. Métiers exploiting pelagic species are often focussed on single species, and are typically seasonal, mid-water trawling (often paired) with mesh sizes less than 70mm. Pelagic métiers account for the majority of landings by over an order of magnitude in several cases. Demersal métiers account for the majority of fishing trips and effort, (primarily Nephrops métiers), and vessels (primarily mixed species métiers). The new métier definitions were found to be appropriate remained relevant despite declining fleet landings and effort between 2003 and 2006. Species compositions within these métiers have generally remained similar to the proportions defined in 2003. These robust métier definitions present opportunities to improve fisheries sampling, assessment and management. Although métiers pose complexity challenge for such applications they can be used the building blocks for appropriate management units. [Copyright &y& Elsevier]

Abstract: Comparative fishing trials investigated the effect of increasing the mesh size in the forward sections of a trawl from 120 and 160mm to (i) 300mm and (ii) 600mm on the catches in the Shetland mixed whitefish fishery. The 300 and 600mm trawls respectively caught an estimated 49 and 75% fewer Atlantic cod (Gadus morhua), 79 and 93% fewer megrim (Lepidorhombus whiffiagonis), 36 and 68% fewer ling (Molva molva), and 28 and 53% fewer hake (Merluccius merluccius) than the control trawl at all lengths. The 300mm trawl caught ∼40% more haddock (Melanogrammus aeglefinus) than the 600mm and control trawls which had similar catch rates. The catch rates for monkfish (Lophius piscatorius) were length dependent and the 300mm trawl caught ∼50% fewer monkfish at 30cm with no significant difference>76cm. The 600mm trawl caught ∼90% fewer monkfish at 30cm with no significant difference>83cm. Both the 300mm and 600mm trawls caught significantly fewer saithe (Pollachius virens) above 53cm. [Copyright &y& Elsevier]

The Laurentian Great Lakes Basin provides an ecological system to evaluate the potential effect of climate change on dynamics of fish populations and the management of their fisheries. This review describes the physical and biological mechanisms by which fish populations will be affected by changes in timing and duration of ice cover, precipitation events and temperature regimes associated with projected climate change in the Great Lakes Basin with a principal focus on the fish communities in shallower regions of the basin. Lake whitefish Coregonus clupeaformis, walleye Sander vitreus and smallmouth bass Micropterus dolomieu were examined to assess the potential effects of climate change on guilds of Great Lakes cold, cool and warm-water fishes, respectively. Overall, the projections for these fishes are for the increased thermally suitable habitat within the lakes, though in different regions than they currently inhabit. Colder-water fishes will seek refuge further north and deeper in the water column and warmer-water fishes will fill the vacated habitat space in the warmer regions of the lakes. While these projections can be modified by a number of other habitat elements ( e.g. anoxia, ice cover, dispersal ability and trophic productivity), it is clear that climate-change drivers will challenge the nature, flexibility and public perception of current fisheries management programmes. Fisheries agencies should develop decision support tools to provide a systematic method for incorporating ecological responses to climate change and moderating public interests to ensure a sustainable future for Great Lakes fishes and fisheries. [ABSTRACT FROM AUTHOR]

Abstract: The results of catch comparison trials of a trawl gear, where the 160mm mesh size netting in the forward sections of the gear is replaced with 300mm mesh size netting, are presented. This gear, which has become known as the ‘Orkney gear’, was designed to reduce, but not eliminate, catches of Atlantic cod in the North Sea mixed whitefish fishery. The results show that the modified gear retains significantly fewer cod smaller than 78cm while, above 78cm, there is no significant difference in the amount of cod caught. Catches of monkfish were 16% less, however, there was no significant difference in the numbers of monkfish caught above 55cm. There was about a 43% loss of megrim across all length classes and there were no losses of haddock and whiting. [Copyright &y& Elsevier]

The conditions for the natural reproduction of whitefish (Coregonus lavaretus) in Lake Constance have been subject to strong variations during recent decades by the impact of fishing and trophic changes. We analysed fluctuations of stock size, age structure, spawning time, and amount of sampled eggs of this species. The onset of spawning altered because of changes in the age structure of the stock. We found a clear relation of spawning time to the mean age of the annual catch and the November epilimnion temperature. The quantity of eggs sampled from the lake bottom with a dredge is in relation to the number of female spawners and may serve as an early indicator for stock size changes. The proportion of viable eggs on the lake floor correlates with oxygen concentrations in deep water. Extremely low oxygen conditions and an almost total loss of eggs occurred when the nutrient levels were high and oxygen regeneration by vertical winter mixing was weak. A mathematical model serves to interpret the changing abundance of living eggs on the lake bottom over the course of a season and is also used to estimate mortality rates. [ABSTRACT FROM AUTHOR]

Aquaculture production has increased rapidly during the last three decades. This is due to increased production of established species as well as a continuous introduction of new species. Productivity growth is the main engine for the increased production in aquaculture, and as the accumulated knowledge is applied to new species and in new regions, production is expected to continue to increase. Along with the production growth an increasing quantity of aquaculture products is being internationally traded. This is rapidly changing several segments of the global seafood market. While high value species such as salmon and shrimp were the first to be traded internationally, low cost species like tilapia and pangasius are currently transforming large parts of the whitefish market. [ABSTRACT FROM AUTHOR]

Declines in growth and condition of lake whitefish Coregonus clupeaformis in Lakes Huron and Michigan have led to increased mean age in the harvest and greater difficulty in scale age interpretation. We evaluated the precision and efficiency of scale acetate impressions, transverse pectoral fin ray sections, and transverse sagittal otolith sections for three lake whitefish stocks (Bailey's Harbor, Naubinway, and Saugatuck) that were sampled in Lake Michigan during 2004 and 2005. We conducted a decision matrix analysis that incorporated capital, production, and personnel costs and precision of age estimates to determine the best aging method given current management priorities. For the Bailey's Harbor stock, age estimates were systematically lower based on scales (mean = 7.85 years) than based on fin rays (8.44 years) or otoliths (8.78 years); fin ray and otolith estimates did not differ significantly. Similar results were observed for both Naubinway and Saugatuck stocks. For Bailey's Harbor lake whitefish, greater precision in age estimates was achieved by use of fin rays (median coefficient of variation [CV] = 4.88%) than by use of scales (5.44%) or otoliths (5.44%). For the Saugatuck stock, age estimates were more precise when obtained from pectoral fin rays (median CV = 4.96%) than from scales, but precision did not differ between fin ray and sagittal otolith ages. Differences between scale and pectoral fin ray age estimates began at age 5 for the Bailey's Harbor stock and at age 6 for the Naubinway and Saugatuck stocks. Differences between scale and sagittal otolith age estimates began at age 5 for the Bailey's Harbor and Saugatuck stocks and at age 8 for the Naubinway stock. Based on the decision matrix analysis, pectoral fin rays provided more-precise estimates and their use involved lower costs than use of the other methods; therefore, pectoral fin rays were deemed the best method for aging lake whitefish in Lake Michigan under current conditions. [ABSTRACT FROM AUTHOR]

Abstract: In this study underwater video footage from cameras placed inside and outside the cod-end was analysed to provide a quantitative description of haddock behaviour inside the cod-end of a commercial whitefish trawl. The behaviour was quantified in terms of orientation, swimming activity, and duration in view of the camera and could be divided into optomotor and erratic swimming behaviour. Optomotor response was the most common behaviour observed, increasing in prevalence with increasing density of fish. Both successful and failed escape attempts were also documented, including location and pre-attempt behaviour. Escapes were concentrated in the areas where meshes were most open, in the rows just ahead of the catch. Over the observed area, between 20 and 35% of the observations of fish approaching and striking the netting resulted in successful escapes. The rate of these netting strikes was generally higher at higher towing speeds and at lower densities. [Copyright &y& Elsevier]

The objective of the study was to test the hypothesis that lake trout populations change in relation to cisco, lake whitefish, round whitefish and burbot populations in lakes in the Algonquin Highlands region of Ontario. Lake trout population change is greatest where cisco and lake whitefish are present. Lake trout populations in lakes without either coregonine tend to have small adults and many juveniles. Where cisco or lake whitefish are present, adult lake trout are large, juvenile abundance is low, and the stock-recruit relationship appears to be uncoupled likely due to a larval bottleneck. Lake trout populations in these lakes may be sensitive to overfishing and recruitment failure. Lake trout populations do not appear to change in relation to round whitefish. There appears to be an indirect positive change on juvenile lake trout abundance through reductions in the density of benthic coregonines in the presence of large, hypolimnetic burbot. [ABSTRACT FROM AUTHOR]

Ferro, R. S. T., Jones, E. G., Kynoch, R. J., Fryer, R. J., and Buckett, B-E. 2007. Separating species using a horizontal panel in the Scottish North Sea whitefish trawl fishery. – ICES Journal of Marine Science, 64: 1543–1550. In the North Sea, Scottish vessels target haddock, cod, whiting, monkfish, saithe, and flatfish in a mixed whitefish trawl fishery. These species mature at different sizes and hence have a range of minimum landing sizes. Their different shapes and swimming capabilities imply different selection characteristics when escaping from trawl gear. However, they are often caught at the same time on the same grounds. Optimal exploitation can only be achieved by ensuring that the selection of each species varies appropriately with length during the fishing process. This paper describes one part of a large European project to develop species-selective trawl gear to improve the exploitation pattern of North Sea cod, while maintaining the catch of other important commercial species. A gear suitable to the Scottish mixed whitefish fishery was fitted with a horizontal panel in the tapered part of the net to separate species into an upper and lower compartment. Trials were conducted on research vessels to measure separation performance for nine species in different light conditions, at different towing speeds, and with different lengths of panel. Most haddock, whiting, and saithe pass above the panel, whereas most cod, flatfish, and monkfish pass below it. Towing speed and panel length had no significant effect on separation. At lower light levels during the night (April at latitude 58° to 61°N), fewer dab, sole, plaice, and cod pass below the panel. Observations and measurements of fish behaviour using acoustic methods are described. They suggest that the height at which fish enter the net mouth may be influenced by light level and water clarity. [ABSTRACT FROM PUBLISHER]

Abstract: While most commercial fisheries in the North Atlantic are strictly regulated through total allowable quotas, licenses and vessel quotas to limit the catch rates, the fishing for blue whiting represents an exception. Today, the blue whiting fishery is out of control; catch rates far exceed what the management authorities propose for a sustainable fishery and there is a real danger for collapse of the stock. The driving force in this development refers to the fact that the coastal states that are involved in the blue whiting fisheries, are not able to agree on the distribution of the migrating blue whiting stock. In Norway, the strong increase in both catch capacity and catch rates, also refers to a liberalization of the institutional framework for the renewal and design of new vessels, but also to structural politics concerning the ocean-going fishing vessels. This article presents the management conflict within the international fisheries for blue whiting and the driving forces behind the capacity increase in the Norwegian blue whiting fleet. However, a future agreement among the coastal nations within the framework of a sustainable fishery, inefficient overcapacity emerges when total quotas and allocation are put on the agenda. This results in allocation conflicts at different management levels that prevent a future solution. The question now is whether regional management organizations like the NEAFC (North East Atlantic Fisheries Committee) should have a more prominent position in the management of resources that migrate through the different coastal states’ economic zones. [Copyright &y& Elsevier]

We investigated the relationships between the pattern of variation of δ13C in pelagic food webs and various morphologic and trophic characteristics of peri-alpine lakes. We used the δ13C of whitefish (Coregonus lavaretus), a long-lived zooplanktivorous fish, to assess the isotope ratio of dissolved inorganic carbon (DIC) at the origin of the pelagic food web. The δ13C of DIC depends on its origin, which may be the atmosphere or the mineralization of organic matter. A synchronic study of 22 peri-alpine lakes shows that the surface area of the lake accounts for much of the variability of the δ13C in pelagic food webs (r2 = 0.76). The δ13C increases with lake size, which suggests that the origin of the DIC integrated into the pelagic food web depends on lake size. To differentiate the influence of trophic status from morphological effects, a diachronic study was performed on the δ13C of fish scales collected over the 20-year re-oligotrophication of Lake Geneva. The δ13C of whitefish increased with phosphorus concentration (r2 = 0.71). This pattern is related to the growing demand for atmospheric DIC as primary production increases. [ABSTRACT FROM AUTHOR]

This paper examines the relationship between causality models and cointegration models in testing for price integration and the Law of One Price (LOP). In our review, we show that cointegration models, which allow for nonstationarity in prices, are a natural extension of the traditional causality methods and not an alternative approach. Hence, the two approaches investigate the same economic hypotheses; however, the choice of modeling method depends on the time series properties of the data. An empirical analysis is provided using prices from the whitefish market in France. With nonstationary price data, the causality approach over rejects the hypothesis of the LOP, whereas conintegration models provide evidence for a well-integrated whitefish market. A generalized version of the composite commodity theorem holds, and prices of most whitefish species can be aggregated into a single commodity price index. [ABSTRACT FROM AUTHOR]

The two-species Schaefer model for species that are captured with the same fishing gear, but which do not interact ecologically, was applied to examine the relation between the maximum sustainable yields for lake trout (Salvelinus namaycush) and lake whitefish (Coregonus clupeaformis) fished together and separately. Lake trout and lake whitefish are two important species in the Laurentian Great Lakes that historically have been Sshed with the same gear. Naturally reproducing lake trout populations have disappeared from most of the Great Lakes, but the lake whitefish supports a large fishery. Application of the logistic surplus production model to lake trout alone does not indicate serious over-exploitation, but applied to lake trout and lake whitefish together indicates that at the total maximum sustainable yield of the two species together, the lake trout is seriously over-exploited and abundance is low. A fishery can be optimized for only one species at a time, and, if several non-interacting species are exploited, some will be over-exploited and some will be under-utilized. One species among several in a multiple species fishery can, in theory, be fished to extinction at the total maximum sustainable yield of the combined species. [ABSTRACT FROM PUBLISHER]

In this article, the author discusses the relevance of length based estimation of condition for the lake whitefish Coregonus clupeaformis against the direct physiological measures used in the fisheries. It mentions the methods used in length based estimates which include electromagnetic pulse (EmP) method, regression quantiles method and relative weight method. It also mentions that the relative length method is based on the mean weights within a specified length class.

The article discusses the results of a survey which determined where, when, and how biological data were being collected from Lake Whitefish harvested by commercial fishers each year. Topics include the complexity of fishery management, building relationships between fisheries professionals and stakeholders, and the need for effective communication for successful fisheries management.

The article presents a dissertation research, which attempts to develop a decision-support tool to ensure that the fish, the fishery, and the livelihoods dependent upon them stay sustainable in light of the climate change. Particular focus is given to a decision-support tool for Great Lakes Lake Whitefish fishery in North America. It estimates the population size of the Lake Whitefish as well as examines which climate factors influence recruitment of Lake Whitefish to the commercial fishery.