Abundance Of Whitefish Research Articles

The spatial and seasonal patterns and stability of the Lake Whitefish fishery in Michigan waters of southern Lake Huron

AbstractObjectiveGiven that the harvested fish from five separate fishing grounds belong to one large mixed population, our objective is to develop an overall abundance index for Lake Whitefish Coregonus clupeaformis in Michigan waters of southern Lake Huron.MethodsWe analyzed catch‐and‐effort data for individual fishing trips to five separate fishing grounds and used Bayesian information criterion to select the best model struture.ResultThe best model included the year × area × month interaction as a random effect, representing the random component in fishery dynamics that were influenced by both fishing practices and fish abundance. The best model also included the fixed effects of area × month interaction, a result consistent with our hypothesis that the seasonal spatial migrations of Lake Whitefish provide the links among the fisheries in separate fishing grounds, and the fishery yields from these separate areas were all dependent on the production in southern Lake Huron as a whole. After adjusting for the random effect of year × area × month interaction and the fixed effects of area × month interaction, the estimated patterns for the fixed year effect indicated that the Lake Whitefish abundance in Michigan waters of southern Lake Huron declined during the late 2000s but has been relatively constant after 2012.ConclusionThe declines in annual fishery yield were due to and could be explained more by the decreases in fish abundance through 2012 but thereafter primarily reflected the declines in annual fishing effort as the fisheries continued to adjust to the changed fishing conditions. We also provided general lessons for studying fisheries without fishery independent surveys but with detailed seasonal and spatial catch‐and‐effort data.

Management of fisheries and restoration of whitefish-nelmushka commercial stocks in Kubenskoye Lake of Vologda Region

The purpose of this article is analysis of the relevance of whitefish commercial fisheries regulation in Kubenskoye Lake and development of measures to preserve the endemic whitefish population, increase its commercial stocks and catches.The material for the study is the statistics of whitefish-nelmushka catches in Kubenskoye Lake and the longterm dynamics of the size and age characteristics, terms of puberty.The research methods: field ichthyological materials were collected and processed according to standard methods; the fishing stocks were estimated based on the results of the analysis of non-water fishing catches, as well as taking into account the volume of water filtered by fixed fishing nets per unit of time.Results: the long-term dynamics of whitefish-nelmushka catches are described in the article. The effectiveness of its fisheries regulation has been studied. Fishing does not have a significant impact on the whitefish abundance dynamics. The exclusion of whitefish from the category of aquatic biological resources, in respect of which the total allowable catch is established, is justified in the article. The size and age population characteristics of the whitefish, age of puberty last years have been summarized in the article.Practical significance: artificial reproduction of the Kubenskoye Lake whitefish is recommended to be carried out to restore the population abundance, which is significant for the preservation of the gene pool of the polymorphic species Coregonus lavaretus. Recommendations on changing the Fishing Rules for the Northern Fishery Basin to reduce the legal size for whitefish-nelmushka were developed for the implementation of commercial and recreation fisheries.

Temporal Population Trends and Habitat Associations for Mountain Whitefish in Central Idaho

AbstractMountain Whitefish Prosopium williamsoni have failed to garner the same level of attention as other members of the salmonid family in terms of scientific investigations, especially with regard to habitat associations and population status. Consequently, we used snorkel survey data from 1985 to 2019 to relate a suite of environmental factors to Mountain Whitefish occupancy and abundance and to estimate population growth rates in central Idaho. Mountain Whitefish population growth rates in the majority of subbasins in central Idaho appear to be stable or increasing over the past several decades, but more so in the Salmon River basin than in the Clearwater River basin. Mountain Whitefish occupancy and abundance were higher in stream reaches that were lower in elevation and gradient and larger in size, with an occupancy rate of <0.10 in stream reaches that were <6 m average wetted width but >0.50 in stream reaches that were ≥9 m average wetted width. Road density was positively associated with the occupancy and abundance of Mountain Whitefish, contrasting previous studies that generally report negative associations between road density and salmonid population metrics. While this relationship may simply be correlative in nature, in the relatively sterile lotic environment of central Idaho, such anthropogenic disturbance may inadvertently result in nutrient enrichment, potentially benefitting the forage base of Mountain Whitefish. We also observed that conductivity positively influenced Mountain Whitefish abundance, likely stemming from its direct effect on stream productivity. Although the status of Mountain Whitefish in central Idaho appears generally stable, the paucity of studies reporting on the status of this species highlights the need for additional research devoted to a better understanding of trends in Mountain Whitefish abundance across their range.

Effect of feeding strategy on digestive tract morphology and physiology of lake whitefish (Coregonus lavaretus)

The common whitefish (Coregonus lavaretus) plays an increasingly important role in European and North American aquaculture industry. At the same time a considerable decrease in whitefish abundance in natural waters is observed. Therefore, it is necessary to develop methods of whitefish rearing not only for commercial but also reintroduction purposes. Fish feeding with natural food (Artemia sp. nauplii) is much more expensive compared to the use of commercial feeds, and thus the attempts to develop optimal feeding strategies have been undertaken to obtain most satisfactory rearing effects at the lowest costs. The aim of the present study was to establish the best moment of commercial feed introduction (Otohime B1) and to evaluate the effects of various feeding strategies on morphological and physiological development of digestive tract in whitefish larvae. This was done using histological analysis of the digestive tract and measurements of digestive enzyme activity. The lowest mortality occurred in the group fed exclusively Artemia sp., while the highest was recorded in the group fed Otohime B1 diet exclusively. Histological analyses revealed no significant pathological alterations in the digestive tract, in all experimental groups. The analysis of digestive enzyme activity revealed the fastest development of gastric glands in fish fed only natural food, however, the intestinal epithelium developed at a similar rate in all groups. The results indicate that the initial feeding of larvae with natural food is not necessary in common whitefish pre-rearing when using the commercial feed Otohime B1, but the highest larval growth was observed in the group which was initially fed Artemia nauplii for one week before the transition to Otohime B1.

Reproductive Ecology, Spawning Behavior, and Juvenile Distribution of Mountain Whitefish in the Madison River, Montana

AbstractMountain Whitefish Prosopium williamsoni were historically common throughout much of the U.S. Intermountain West. However, within the last decade Mountain Whitefish have exhibited population‐level declines in some rivers. In the Madison River, Montana, anecdotal evidence indicates Mountain Whitefish abundance has declined and the population is skewed toward larger individuals, which is typically symptomatic of recruitment problems. Describing reproductive development, spawning behavior, and juvenile distribution will form a foundation for investigating mechanisms influencing recruitment. We collected otoliths and gonadal samples from fish of all size‐classes to characterize fecundity, age at maturity, and spawning periodicity. We implanted radio tags in mature Mountain Whitefish and relocated tagged fish in autumn 2012–2014. Timing of spawning was determined from spawning status of captured females and from density of eggs collected on egg mats. In spring 2014, we seined backwater and channel sites to describe age‐0 whitefish distribution. Mountain Whitefish were highly fecund (18,454 eggs/kg body weight) annual spawners, and age at 50% maturity was 2.0 years for males and 2.6 years for females. In 2013 and 2014, spawning occurred between the third week of October and first week of November. During spawning, spawning adults and collected embryos were concentrated in the downstream 26 km of the study site, a reach characterized by a complex, braided channel. This reach had the highest CPUE of age‐0 Mountain Whitefish, and the percentage of spawning adults in the 25 km upstream from a sampling site was positively associated with juvenile CPUE. Within this reach, age‐0 Mountain Whitefish were associated with silt‐laden backwater and eddy habitats. Future investigations on mechanisms influencing recruitment should be focused on the embryological phase and age‐0 fish.Received June 19, 2016; accepted March 28, 2017 Published online July 24, 2017

Changes in autumn zooplankton in the pelagic zone of Lake Sevan (Armenia) during the increase in fish abundance

The qualitative composition and structure of the autumn zooplankton in the pelagic zone of Lake Sevan in years that were characterized by different abundancies of fish are described. In October 2013, upon the increase in whitefish abundance, the species richness of zooplankton increased insignificantly; the values of the trophic coefficient and the Shannon index, calculated by the number, increased; and the specific number of Rotifera and Cladocera decreased. At the same time, atypical changes were recorded in the development parameters of zooplankton invertebrates. They were expressed as an increase in the total biomass due to Cladocera, among which large Daphnia (Ctenodaphnia) magna Straus occupied the leading position. The possible reasons for the particular changes in zooplankton are discussed.

Thermal habitat segregation among morphotypes of whitefish (Coregonus lavaretus: Salmonidae) and invasive vendace (C. albula): a mechanism for co‐existence?

Summary Aquatic invasive species can have a variety of negative impacts on the ecosystems they invade. Carbon and nitrogen stable isotopes in the muscle tissue of aquatic organisms have proved useful for evaluating post‐invasion dietary shifts among species. However, oxygen and carbon stable isotopes in fish otoliths have the potential to provide additional data on thermal habitat, diet and metabolism, when investigating interactions among sympatric native and invasive fishes. We conducted oxygen and carbon stable isotope analysis on the otoliths of three morphotypes of native whitefish (Coregonus lavaretus) and invasive vendace (Coregonus albula) at two sites within the sub‐Arctic Pasvik watercourse in northern Norway. Mean temperature use among morphotypes and species over the course of the growing season ranged from 7.5 °C to 11.2 °C. Otolith δ13C was significantly positively correlated to fish muscle tissue δ13C (P < 0.05, r2 = 0.53). Significant differences in temperature use and δ13C among morphotypes and between species were found in the downstream site but not the upstream site. Complementary partitioning of thermal and dietary resource use in the downstream site coincides with a higher abundance of whitefish, enabling the coexistence of both species. In contrast, vendace were dominant in the upstream site where no differentiation in resource use among morphotypes and between species was evident. This study demonstrates the usefulness of stable oxygen and carbon otolith isotopes for characterising resource use and highlights the importance of investigating thermal habitat use as a factor influencing the success of invasive fishes.

Larval Lake Whitefish abundance, diet and growth and their zooplankton prey abundance during a period of ecosystem change on the Bay of Quinte, Lake Ontario

Studies to examine larval Lake Whitefish (Coregonus clupeaformis) abundance, diet composition and growth, and the abundance of their zooplankton prey were conducted during eight years (1991–1993, 1995–1996 and 2003–2005) over the course of two decades that spanned a period of major ecosystem change—primarily dreissenid mussel related impacts—on the Bay of Quinte, northeastern Lake Ontario. Larval fish were captured in shallow, nearshore waters (0.2–2.0 m) from early April to mid-May each year. Larval Lake Whitefish fed primarily on cyclopoid copepods and small-bodied cladocerans. The key finding of our studies was that prey abundance declined by 89% from the earlier (1991–1993, 1995–1996) to the later (2003–2005) sampling years. Larval fish growth during spring was significantly correlated with prey availability. Recruitment to the juvenile stage in August was correlated with spring prey availability and larval fish growth. The observed decline in larval Lake Whitefish prey in the Bay of Quinte may be contributing to poor stock performance during and following a period of significant ecosystem change.

Environmental Factors Related to the Distribution, Abundance, and Life History Characteristics of Mountain Whitefish in Idaho

AbstractMountain whitefish Prosopium williamsoni are a broadly distributed native salmonid in western North America, but comparatively little investigation has been made regarding their population characteristics. We surveyed 2,043 study sites to assess whether physiochemical stream conditions affected mountain whitefish distribution and abundance in southern Idaho, and at 20 of these sites life history characteristics were also estimated. A total of 581 sites were dry or contained too little water to support any fish species. Mountain whitefish were captured at 106 sites; for these sites only, mean abundance was 2.2/100 m2. They were rarely present when mean wetted width was less than 10 m but were almost always present when wetted width was greater than 15 m. We estimated that within the study area there were approximately 4.7 ± 1.8 million mountain whitefish, mostly in fifth‐ to seventh‐order streams, which comprised only 13% of the total stream kilometers but accounted for 93% of the total abundance of whitefish. Growth was positively related to mean annual water temperature and negatively related to site elevation. Mountain whitefish were long lived, most (90%) populations containing fish estimated to be at least 10 years old. This longevity produced total annual survival rates averaging 0.82 (range = 0.63–0.91). In general, the growth, fecundity, and survival of mountain whitefish were higher in the upper Snake River basin than in other areas for which data have been reported. Whitefish matured at about 250 mm and about age 2, with little variation in length and age at maturity between sites; males matured at a smaller size and younger age than females. The disproportionate use of larger (i.e., >15‐m‐wide) streams by mountain whitefish in southern Idaho differs from the situation in more northerly locations, where they apparently are more common in smaller streams.

Developing Model‐Based Indices of Lake Whitefish Abundance Using Commercial Fishery Catch and Effort Data in Lakes Huron, Michigan, and Superior

AbstractFishery catch per effort (CPE) is often used to assess relative fish abundance, and in many Great Lakes and other freshwater applications the CPE index is based on either an average or the ratio of summed aggregate catch to summed aggregate effort. In particular, assessments used to estimate the abundance of lake whitefish Coregonus clupeaformis and recommend harvest quotas in 1836 Treaty‐ceded waters of Lakes Huron, Michigan, and Superior assume that commercial CPE from gill‐net and trap‐net fisheries is proportional to abundance; however, CPE may change due to factors other than abundance, leading to violations of this assumption. To account for sources of CPE variation that are not attributable to abundance, general linear mixed models (GLMMs) were developed for each management unit and least‐squares means (LSMs) for each year were used as the index of abundance. The effect of using the GLMM method for standardization was evaluated by examining the temporal trends in the proportional difference between LSMs and CPE (i.e., aggregate catch divided by aggregate effort for each year). Of the random effects included in the final GLMM for the gill‐net fishery, license holder accounted for the most variation. The fixed effect of boat size category on CPE depended on lake; on average, there was little difference between boat sizes in Lake Superior, whereas large boats had a lower CPE than medium and small boats in Lakes Michigan and Huron. On average, CPE was higher from October to December than during other months. The proportional difference between LSMs and CPE trended through time in some management units, suggesting the importance of adjusting fishery CPE for effects like boat size, season, and license holder. Factors that influence lake whitefish commercial fishery CPE are similar to factors important for marine commercial fisheries.

Lake Whitefish Relative Abundance, Length-at-Age, and Condition in Lake Michigan as Indicated by Fishery-independent Surveys

In the mid 1990s, growth and condition of lake whitefish (Coregonus clupeaformis) declined within commercial catches in Lake Michigan. However, underlying mechanisms responsible for the declines have not been thoroughly explored. Using fishery-independent survey data, we examined growth and relative abundance of adult whitefish over historical (1980–1990) and recent (1996–2005) time periods in three regions of Lake Michigan: north, mid, and south. Relative abundance was assessed from catch-per-unit-effort (CPUE) of independent surveys, and changes in growth conditions were evaluated using size-at-age estimates. Relative abundance increased in the mid and south regions between the two time periods and decreased in the north region. Length-at-age significantly declined between the two time periods in the north, mid, and south regions; the north region consistently had the lowest length-at-age. Condition also declined between the two time periods in each region. The decline in growth and condition coupled with increases in relative abundance suggest density-dependent mechanisms are contributing to the observed population changes in the south region. The north region does not appear to be regulated by density, suggesting density-independent mechanisms, such as food web changes, are influencing stocks. Changes in the mid region are likely from a mixture of increased lake whitefish abundance and food web changes. Using fishery-independent population data, our results suggest that multiple factors are potentially contributing differentially within three Lake Michigan regions to cause similar declines in length-at-age and condition of whitefish. These factors (e.g., food web changes, lake whitefish density) should be considered when managing the commercial fishery.

Changes in Fecundity and Egg Lipid Content of Lake Whitefish ( Coregonus clupeaformis) in the Upper Laurentian Great Lakes between 1986–87 and 2003–05

Lake whitefish ( Coregonus clupeaformis Mitchill), an important commercial species in the Laurentian Great Lakes, have experienced decreased growth and condition in regions of the upper Great Lakes over the past 20 years. Increases in lake whitefish density and decreases in the density of Diporeia spp., an energy rich and historically important part of the lake whitefish diet, have been implicated in the recent declines in lake whitefish growth and condition. The goal of this study was to describe lake whitefish fecundity, egg lipid content, and total ovary lipid content in selected regions of Lakes Huron, Michigan, and Superior in 1986–87 and 2003–05, two time periods with different lake whitefish and Diporeia densities. Under conditions of high lake whitefish density and low Diporeia density, female lake whitefish in the upper Laurentian Great Lakes generally produced fewer eggs. Egg lipid content was higher in 2003–05 than in 1986–87 at all sites, regardless of changes in lake whitefish or Diporeia densities. Total ovary lipid content and lake whitefish abundance were inversely related, while there was no significant relationship between total ovary lipid content and Diporeia density. The amount of energy that lake whitefish invested in egg production was more closely associated with lake whitefish abundance than with Diporeia density. This study provides evidence that recent changes in production dynamics of Great Lakes lake whitefish have not been driven solely by declines in Diporeia but have been significantly influenced by lake whitefish abundance.

Back again: The reappearance of Diaphanosoma brachyurum in Lake Constance

Diaphanosoma brachyurum disappeared from the cladoceran community of Lake Constance in 1962 but reappeared in 2001. The disappearance coincided with eutrophication and the reappearance with oligotrophication of the lake. This was surprising, as Diaphanosoma brachyurum is often characterized as a species that favours meso- to eutrophic habitats. In 2001, the cladoceran occurred from late summer until autumn reaching maximum density in September that coincided with a high density of small algae. Vertical distribution of Diaphanosoma brachyurum was typically restricted to the upper 10m to 20m of the water column. Besides oligotrophication, the reappearance coincided with a low abundance of whitefish, Leptodora kindtii and Daphnia galeata. Although the ultimate cause is unknown, reduced predation and competition likely contributed to the reappearance of Diaphanosoma brachyurum in Lake Constance.

Validation of Lake Whitefish Catch-Per-Unit-Effort Data with Time Series Analysis

Catch-per-unit-effort (CPUE) data for lake whitefish Coregonus clupeaformis in Michigan waters of Lake Huron were examined with time analysis to test if they can describe the abundance of lake whitefish. Relations between lake whitefish CPUE and environmental and biological data were investigated with cross-correlation analysis. A 4-year time lag, corresponding to the age at maturity, was found for lake whitefish CPUE. Cross-correlation analysis indicated that lake whitefish CPUE was negatively correlated with monthly air temperatures and abundance of sea lamprey Petromyzon marinus in previous years, and CPUE was positively correlated with fishing effort 1 year later. The results indicated that fishermen track lake whitefish abundance and that CPUE can describe fluctuations of the lake whitefish population.

Changes in the Multispecies, Winter Angling Fishery of Lake Simcoe, Ontario, 1961–83: Invasion by Rainbow Smelt,Osmerus mordax, and the Roles of Intra- and Interspecific Interactions

Winter creel surveys revealed major changes in the abundance of five fish species (lake trout, Salvelinus namaycush, lake whitefish, Coregonus clupeaformis, lake herring, Coregonus artedii, yellow perch, Perca flavescens, and rainbow smelt, Osmerus mordax) in Lake Simcoe (1961–83). Variations in abundance were in part caused by intra- and interspecific factors. Catches in alternate years for both lake herring and rainbow smelt were inversely correlated, suggesting negative interactions between their young-of-the-year and yearlings. Similarly an inverse relation between parental stock size and recruitment explained a significant component of the catch variation of lake herring and yellow perch. Natural recruitment of lake trout declined during the 1950s (associated with eutrophication effects), and in the early 1960s, rainbow smelt invaded the fake. Lake whitefish abundance declined in the early 1970s as smelt abundance increased; the decline in whitefish recruitment was probably caused by interaction between smelt and whitefish young-of-the-year. Catches of yellow perch were positively correlated with rainbow smelt and negatively correlated with lake whitefish. Lake herring also increased when lake whitefish density was low. Increased abundance of lake trout after 1975 (due to stocking) appears to have resulted in lower densities of lake herring, rainbow smelt, and yellow perch and the reestablishment of lake whitefish recruitment at a low level. These results suggest that a large predator (lake trout) can have a major influence on the structure of a fish community, by direct and indirect effects.

Tagging Returns, Age Studies and Fluctuations in Abundance of Lake Winnipeg Whitefish, 1931–1951

On the basis of 2,003 lake whitefish, Coregonus clupeaformis, tagged in 1938, of which 126 were recovered during the next five years, there is evidence that fish released together tend to stay together for years, and that the proportion of a population captured during a certain time by a unit amount of fishing effort can fluctuate greatly (a plausible explanation is the effect of variations in weather conditions). On the basis of age determinations of 12,975 whitefish in samples taken annually from 1937 to 1951, growth rate was determined, the total annual mortality rate among fully exploited fish was calculated to be 64 per cent over several years, and it appeared that all year-classes had been of about equal strength in recent years. The generally accepted idea that fluctations in fishing success correspond to fluctuations in abundance of whitefish is probably erroneous. Possibly the Lake Winnipeg whitefish are underfished.

Rapid electrolysis without rotating electrodes: Graham Edgar and P. B. Purdum, of the University of Virginia ( Jour. Am. Chem., Soc., 1922, xliv, 1267–1270)

Lake whitefish (Coregonus clupeaformis Mitchill), an important commercial species in the Laurentian Great Lakes, have experienced decreased growth and condition in regions of the upper Great Lakes over the past 20 years. Increases in lake whitefish density and decreases in the density of Diporeia spp., an energy rich and historically important part of the lake whitefish diet, have been implicated in the recent declines in lake whitefish growth and condition. The goal of this study was to describe lake whitefish fecundity, egg lipid content, and total ovary lipid content in selected regions of Lakes Huron, Michigan, and Superior in 1986–87 and 2003–05, two time periods with different lake whitefish and Diporeia densities. Under conditions of high lake whitefish density and low Diporeia density, female lake whitefish in the upper Laurentian Great Lakes generally produced fewer eggs. Egg lipid content was higher in 2003–05 than in 1986–87 at all sites, regardless of changes in lake whitefish or Diporeia densities. Total ovary lipid content and lake whitefish abundance were inversely related, while there was no significant relationship between total ovary lipid content and Diporeia density. The amount of energy that lake whitefish invested in egg production was more closely associated with lake whitefish abundance than with Diporeia density. This study provides evidence that recent changes in production dynamics of Great Lakes lake whitefish have not been driven solely by declines in Diporeia but have been significantly influenced by lake whitefish abundance.