Humpback Whitefish Research Articles

Reproductive biology of female humpback whitefish Coregonus pidschian in the Chatanika River, Alaska

Summary Humpback whitefish Coregonus pidschian are found throughout Alaska and support both subsistence and personal-use fisheries. Long-term sustainability of these fisheries requires an understanding of life-history characteristics and reproductive biology to provide fisheries managers with the tools required for science-based management. The objective of this study was to examine the reproductive characteristics of humpback whitefish in the Chatanika River, Alaska, from late August through September 2008. Absolute fecundity, relative fecundity, gonadosomatic index (GSI), relative egg size, and age were examined for 60 female humpback whitefish. Mean absolute fecundity was 45 000 eggs female−1 (range, 11 747–108 426 eggs female−1) and was positively related to both fork length (r2 = 0.74) and wet weight (r2 = 0.83). Gonadosomatic index values averaged 15.5% (range, 6.4–23.7%). Relative fecundity was positively related to GSI (r2 = 0.76) and showed a positive relationship with age until ages 15–20 before declining thereafter. Relative egg size was inversely related to GSI (r2 = 0.38) and age (r2 = 0.22) for female humpback whitefish. The results of our study provide information that will allow for better management of the personal use fishery for humpback whitefish in the Chatanika River and increase our understanding of the reproductive biology of this species throughout its geographic distribution.

Freshwater Mollusks Survive Fish Gut Passage

Freshwater mollusks figure prominently in the diets of humpback whitefish (Coregonus pidschian) and broad whitefish (C. nasus), two benthic-feeding coregonid species. A recent examination of pea clams (Sphaeriidae), valve snails (Valvatidae), and pond snails (Lymnaeidae) from the lower digestive tracts of these fish found that many of the mollusks were alive. Survival completely through gut passage would indicate a dispersal mechanism for freshwater mollusks that has not been previously recognized. A field investigation was conducted with wild-caught humpback and broad whitefish to test the hypothesis that clams and snails are capable of surviving complete gut passage. Wild fish were captured alive and held in collection totes to obtain feces samples. Pea clams and valve snails were abundant in fish feces, and pond snails were present but not abundant. An average of 483 pea clams and 833 valve snails per fish were observed to have survived complete gut passage, while only a single surviving pond snail was found. These findings suggest that fish may play an important role in the dispersal of freshwater mollusks within freshwater systems.

Otolith Trace Element Chemistry as an Indicator of Anadromy in Yukon River Drainage Coregonine Fishes

AbstractEight coregonine species have been documented in the Yukon River drainage. They include inconnuStenodus leucichthys, broad whitefishCoregonus nasus, humpback whitefishC. pidschian, Alaska whitefishC. nelsonii, least ciscoC. sardinella, Bering ciscoC. laurettae, round whitefishProsopium cylindracium, and pygmy whitefishP. coulterii. Personal use, sport, and commercial fisheries within the drainage target several of these species. Some species are capable of anadromous life histories, as evidenced by their presence in estuaries, yet few studies have investigated the upstream migrations of anadromous components of these populations. Only inconnu migrations have been previously examined in the Yukon River drainage. We investigated the distribution of anadromous coregonine fish in the Yukon River drainage in Alaska using sampling and otolith chemistry procedures. Six species were identified in sample collections from eight regions of the drainage between 1,200 and 2,000 km upstream from the Bering Sea. Gonadosomatic indices indicated that most sampled fish of all species were mature and preparing to spawn. Anadromous inconnu, broad whitefish, and humpback whitefish were distributed in the Yukon River and its tributaries to a maximum distance of 1,700 km from the sea. Anadromous least cisco were distributed in the Yukon River and its tributaries up to 1,600 km from the sea, whereas anadromous Bering cisco were present in the Yukon River main stem as far upstream as 2,000 km. No anadromous round whitefish were detected. Few coregonine spawning areas have been identified, so the actual migration distances of anadromous species may be greater than presented here.

A versatile net selectivity model, with application to Pacific salmon and freshwater species of the Yukon River, Alaska

Gillnet catch data from the lower Yukon River, AK, collected from 1990 to 2003 in conjunction with a sonar study to estimate the abundance of migrating fish, were assembled. The full dataset contained 92,029 records with complete species and length information. A subset of data for the eight most prevalent groups of fish was selected for the estimation of net selectivity. The reduced dataset contained 89,984 records for Chinook salmon (Oncorhynchus tshawytscha), summer and fall runs of chum salmon (O. keta), coho salmon (O. kisutch), pink salmon (O. gorbuscha), humpback whitefish (Coregonus pidschian), broad whitefish (C. nasus), and various cisco (Coregonus) species. A Pearson function was used as a net selectivity model for all eight groups of fish, though a parameter was added to accommodate the catch of fish that are relatively large for a particular mesh. Because most of these relatively large fish were probably not gilled, but rather caught by body parts other than the operculum, the extra parameter can be thought of as a tangling parameter. The parameters of the modified Pearson model were estimated using maximum likelihood, and variances were estimated through bootstrapping. Gillnets were found to be most efficient, for all eight groups of fish, when fish length is approximately twice as great as the perimeter of a mesh, and the corresponding location parameter of the Pearson model was estimated with high precision. As the Pearson function has apparently not been used previously as a net selectivity model, its suitability was compared to the normal, lognormal, gamma, inverse Gaussian, and bi-normal functions, which are commonly employed as net selectivity models. Model fit was evaluated on the basis of the value of the likelihood function obtained, Akaike's Information Criterion and scaled deviance statistics, and plots of estimated models and scaled catch data. The Pearson model was found to be quite flexible, and fit the data as well as or better than the other models for all eight groups of fish considered. Other researchers may wish to consider its use with their data.

Using perceptions of data accuracy and empirical weighting of information: assessment of a recreational fish population

Recreational fisheries management is often compromised by limited information of variable quality from several sources. We develop a form of catch-age analysis to combine uncertain information from creel surveys, age composition, and mark-recapture estimates of abundance. Four systems are used in weighting annual observations: equal, inverse of squared coefficients of variation (CV-2), perceptions of accuracy, and a combination of the latter two. The model is applied to a humpback whitefish (Coregonus pidschian) population in Alaska and evaluated for model fit, parameter uncertainty, conservative forecasts of exploitable abundance, and biological plausibility. The probability of forecasted stock abundance occurring below a threshold level defined by an agency management plan is evaluated for various recruitment and exploitation scenarios. The perception model is judged to be best with the use of the analytic hierarchy process, a decision-making technique. By incorporating perceptions into fisheries decision-making, beliefs in the accuracy of uncertain information are made explicit. In a conservative context, fishery management decisions should include reducing risk to the stock in the setting of harvest policy and in the selection of the assessment model.

The Effect of New Breaching in a Prudhoe Bay Causeway on the Coastal Distribution of Humpback Whitefish

West Dock is a solid-gravel petroleum production causeway 4.3 km long that was constructed along the Beaufort Sea coast near Prudhoe Bay, Alaska, in the late 1970s. In the winter of 1995-96, a breach 200 m wide was constructed 1 km from the base of the causeway. Fish monitoring studies conducted during the summers of 1996 and 1997 indicated that the catch of adult (>= 200 mm fork length) humpback whitefish (Coregonus pidschian) had increased significantly east of West Dock relative to levels observed in the 11 previous years. Data suggest that humpback whitefish dispersing eastward along the coast from their overwintering grounds in the Colville River had been blocked from moving east of West Dock and that construction of the breach has allowed these fish to extend their summer foraging range farther to the east.

Fecundity of Humpback Whitefish and Least Cisco in the Chatanika River, Alaska

Abstract Fecundity of 93 humpback whitefish Coregonus pidschian and 80 least ciscoes C. sardinella collected from the Chatanika River, Alaska, was estimated with volumetric methods. Measurement errors in estimates of fecundity were small relative to estimates; coefficients of variation (100·SE/mean) for 32 test cases ranged from 0.3 to 12.1%, and they were less than 5% in 28 of the 32 test cases. Predictive regressions were used to predict fecundity from fork length (FL). Fecundity ofhumpback whitefish ranged from 8,400 to 65,400 eggs per female for fish 320 to 520 mm FL. Fecundity for least cisco ranged from 11,500 to 111,600 eggs per female for fish 280 to 420 mm FL. Although length compositions of spawning humpback whitefish and feast cisco in the Chatanika River have decreased substantially since the early 1970s, the length-fecundity relationships can still be used to develop estimates of egg deposition.

Micropyle of some salmonins and coregonins

The micropyle of seven salmonins and four coregonins were examined by a scanning electron microscope. In addition, the micropyle of Coregonus pidschian is described for the first time. The micropyles and the surface pattern may be used for identification of eggs. The studied micropyle belongs to two different types: 1. micropyle with flat pit and long canal (type II) and 2. micropyle with canal but without pit (type III). The sides of the micropyle canal are often reinforced by annular or helicoid thickening.

Contributions to the Life History of the Humpback Whitefish in Alaska

Modal gill raker counts of Coregonus pidschian from various areas of Alaska ranged from 21 to 26, with populations of coastal streams having lower counts. Humpback whitefish are mainly distributed north of the Alaska Range and are found in lakes, streams, and brackish water. Feeding migrations into lake and slough areas of many Alaskan waters occur soon after ice breakup, with an outmigration occurring during freeze-up. Many spawning populations migrate upstream during summer and fall and spawn in upper reaches of rivers. Spawning generally occurs during late September and October over gravel bottoms. Humpback whitefish studied reached 540 mm fork length and age XIV. Populations from interior Alaska waters grow faster than coastal populations, with Chatanika River fish reaching 442 mm at age VIII. First maturity is usually reached between ages V and VII. Main utilization of the humpback whitefish in Alaska is for subsistence but small commercial and sport fisheries exist in interior Alaska.

On the seasonal migrations of the river-spawning whitefish, Coregonus pidschian (Gmelin), in an arctic watercourse

(1975). On the seasonal migrations of the river-spawning whitefish, Coregonus pidschian (Gmelin), in an arctic watercourse. SIL Proceedings, 1922-2010: Vol. 19, No. 4, pp. 2538-2545.

Keller Lake: Characteristics of a Culturally Unstressed Salmonid Community

Keller Lake, with an area of 413 km2, is an essentially unexploited lake in the Northwest Territories. Results of an experimental fishery and a commercial fishery of short duration are described. Effects of gillnet selection are discussed for the two major species, lake trout and humpback whitefish, and it is concluded that the sample obtained represents the actual population, at least for sizes over 350 mm in length. There were very few fish in the 350–500 mm size range, or in age-groups 9–13; but size and age were not closely correlated. The population structure is likened to a forest climax condition. A mechanism for the dynamics of the system is proposed, which can be tested. Size distribution of the population is considered to be in the form of a standing wave with the shape of a normal distribution for the main body of the population; age structure changes with time but will retain a bimodal condition continuously. The effect of cropping on a population structure of this type is discussed.

Sympatric Occurrence of Two Species of Humpback Whitefish in Squanga Lake, Yukon Territory

Squanga Lake in the Canadian headwaters of the Yukon River contains two species of humpback whitefish, characterized by modal first arch gill raker counts of 23 and 28 but with overlap in the range of counts. The species can be separated more sharply by raker counts of the second arch, also with modes of 23 and 28. Seven other morphometric characters not correlated with gill raker count each have significantly different means, but some overlap, between the species.In June the species with high raker count mainly occupies the pelagic zone, while the low count species occupies the bottom layers at all depths. The high count species feeds mainly on plankton, the low count species on bottom organisms. The high count species spawns in inlet and outlet streams in November and December. Gonad development in June suggests that the low count form spawns later, in localities unknown. Samples from early winter spawning runs contained exclusively high count individuals. A few fish, probably hybrids, had raker count corresponding to one species and most other morphological characters corresponding to the other. Tentative names for the species are Coregonus clupeaformis (high gill raker count) and Coregonus pidschian.