Randy J. Brown

Otolith chemistry analyses indicate that water Sr:Ca is the primary factor influencing otolith Sr:Ca for freshwater and diadromous fish but not for marine fish

Water chemistry is thought to be the primary factor influencing fish otolith chemistry. Experimental results with freshwater and diadromous fish have been consistent with this paradigm, but with marine fish, they have often been ambiguous or contradictory. A review of water chemistry data indicated that Sr:Ca (mmol:mol) levels were higher in marine water than in most freshwater systems and that Sr:Ca variability was lower in marine water than in most freshwater systems. We therefore hypothesized that lifetime otolith Sr:Ca profiles of freshwater fish would exhibit low levels of Sr:Ca with moderate variability, of diadromous fish would exhibit highly variable Sr:Ca levels, and of marine fish would exhibit high levels of Sr:Ca with low variability. Otolith Sr:Ca profiles from 81 species of freshwater, diadromous, and marine fish revealed that freshwater fish had low levels of Sr:Ca and lower variability than expected relative to marine fish, diadromous fish had Sr:Ca levels and variability that were consist...

Otolith trace element chemistry as an indicator of anadromy in yukon river drainage coregonine fishes

Abstract Eight coregonine species have been documented in the Yukon River drainage. They include inconnu Stenodus leucichthys, broad whitefish Coregonus nasus, humpback whitefish C. pidschian, Alaska whitefish C. nelsonii, least cisco C. sardinella, Bering cisco C. laurettae, round whitefish Prosopium cylindracium, and pygmy whitefish P. 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 Be...

Direct Validation of Annual Growth Increments on Sectioned Otoliths from Adult Arctic Grayling and a Comparison of Otolith and Scale Ages

Abstract Accurate ages are essential for the responsible management of fish populations, and validation of ages ensures that accurate age estimates are available to managers. Scales have typically been used to estimate ages of Arctic grayling Thymallus arcticus in Alaska; however, the recapture of marked fish after several years at large has cast doubt on the accuracy of scale ages for this species. To validate age determinations from otoliths, we used oxytetracycline (OTC) to mark 102 Arctic grayling from the Eldorado River, Seward Peninsula, Alaska, during 1994 and 1995. Fish were tagged, fin-clipped, weighed, and injected with 25 mg of OTC/kg of body weight. Over the succeeding 4 years, 16 OTC-marked Arctic grayling were recaptured. Fluorescent marks were visible in thin-sectioned otoliths from 15 of the 16 recaptured fish, and annuli that were visible beyond the mark accurately recorded the passage of years between mark and recapture in all otoliths with OTC marks. Ages assigned from scales underestim...

DNA Barcoding of Eight North American Coregonine Species

Coregonine fishes have a circumpolar distribution in the Arctic and sub‐Arctic Northern Hemisphere. This subfamily of Salmonidae consists of three genera: Prosopium, Stenodus and Coregonus, including over 30 species. Many species overlap spatially and are difficult to distinguish based on morphological characteristics, especially as larvae or juveniles. Here we present a method for rapid and cost‐effective species identification for representatives of the three genera based on sequence variation at the mitochondrial cytochrome c oxidase subunit I gene (COI). We examined eight species common to North America with distributional overlap in Alaska. Mean pairwise sequence divergence for all eight species was 7.04% and ranged from 0.46% to 14.23%. This sequence variation was used to develop a genetic assay based on restriction fragment length polymorphism. In a blind test, this assay provided correct species assignment for 48 of 49 individuals representing all eight species. The single incorrect assignment may reflect hybridization between two closely related species. This DNA barcode‐based assay promises to aid fishery managers and researchers by providing a cost‐effective alternative to large‐scale sequence analysis for identification of North American coregonine fishes.

Determining the Movements and Distribution of Anadromous Bering Ciscoes by Use of Otolith Strontium Isotopes

AbstractMethods for tracking the movements and distribution of fishes have often involved expensive field logistics, which is compounded in remote regions such as Alaska. An alternative approach is to use the chemical signatures preserved in the otoliths of teleost fish to track their movement history. We used the strontium isotope signature (87Sr/86Sr) preserved in the freshwater portion of otoliths taken from Bering Ciscoes Coregonus laurettae to identify their natal river of origin and their movements. Bering Ciscoes spawn in freshwater rivers and rear in coastal marine waters. Just three spawning rivers are known for this species worldwide: the Yukon, Kuskokwim, and Susitna rivers. Rearing commonly occurs in coastal estuaries and lagoons along the Arctic coast of Alaska, the Yukon–Kuskokwim (Y–K) delta, and (rarely) the Alaska Peninsula. We compiled a set (n = 127) of Bering Cisco otoliths from fish caught in coastal marine habitats within each of these rearing areas. We measured the 87Sr/86Sr values ...

Catalog of Chinook Salmon Spawning Areas in Yukon River Basin in Canada and United States

Abstract Chinook Salmon Oncorhynchus tshawytscha return to the Yukon River in northwestern North America each summer, migrating to spawning destinations from the lower river to more than 3,000 km upstream. These returns support numerous fisheries throughout the basin. Despite a long history of fisheries research and management, there is no comprehensive account of Chinook Salmon spawning areas in the basin. To address this issue, we cataloged, summarized, and mapped the known spawning areas of Yukon River Chinook Salmon by using a variety of sources including published articles, gray literature, and information archived in agency databases. Most of our sources were published within the past 30 y, but some refer to observations that were recorded as long ago as the late 1800s. We classified spawning areas as major or minor producers with three indicators of abundance: 1) quantitative estimates of escapement (major producer if ≥500 fish, minor producer if <500 fish), 2) radiotelemetry-based proportions of a...

Contemporary factors influencing genetic diversity in the Alaska humpback whitefish Coregonus clupeaformis complex: alaska c. clupeaformis genetic diversity

Thirteen microsatellite loci were used to address three hypotheses regarding genetic diversity in the humpback whitefish Coregonus clupeaformis complex in Alaska. The test results provided further insight into the factors influencing C. clupeaformis complex population structure and level of genetic variation. First, the microsatellite data did not provide evidence of two spatially distinct Beringian and Eurasian refugial groups as revealed in previous phylogeographic analyses of mitochondrial DNA variation. Rather, the population structure inferred from the microsatellite variation appears to reveal the influence of factors on a more recent time scale, including gene flow among the refugial groups and isolation of some anadromous and freshwater resident populations. Second, anadromous C. clupeaformis complex collections exhibited higher intra-population genetic diversity than freshwater resident collections. This outcome is consistent with previous meta analyses suggesting that freshwater resident populations probably have smaller historical effective population sizes and less conspecific gene flow because the habitat tends to be smaller and supports fewer and smaller populations. Finally, the analysis of contemporary immigration rates was consistent with, but did not provide statistical support for, the hypothesis that gene flow among anadromous C. clupeaformis complex populations along coastal Alaska is influenced by the Alaska Coastal Current. Further studies are needed to evaluate gene flow among coastal Alaska C. clupeaformis complex populations.