Emergence timing and subsequent downstream movements of two non-native salmonids in a Lake Superior tributary

We describe patterns of emergence and downstream movement by recently emerged fry of two non-native salmonids in the Great Lakes region, North America. Our primary objectives were to describe the timing of emergence in relation to spring flooding, and to examine the effects of reach-level complexity of stream habitat on rates of movement. Emergence and movement patterns of coho salmon and brown trout fry were assessed over an eight-week period in two reaches distinguished by differences in channel woody debris. Fry emergence occurred from mid-March to early May, and peaked in early to mid-April. Movement during this period was uncorrelated with upstream densities of resident fry and fish moving downstream did not appear moribund or in poor condition. Nearly twice as many fish moved through the simple reach that lacked woody debris cover even though upstream densities of resident fry were generally greater in the complex reach. The results reported here indicate that peak emergence occurs in close association with the timing of spring floods. Variability in the timing of either emergence or spring floods could have profound effects on the size of coho salmon and brown trout populations within streams of this region. Results from this study further suggest that greater habitat complexity may reduce downstream movements of newly emerged salmonid fry in a natural system.     

DNA barcoding vs. morphological identification of larval fish and embryos in Lake Huron: Advantages to a molecular approach

The Great Lakes provide habitat to over 160 species of freshwater fish, many of which are ecologically and economically important. Concern for management and conservation of declining fish populations makes it important that accurate identification techniques are used for environmental monitoring programs. DNA barcoding may be an effective alternative to morphological identification for industrial monitoring programs of larval and embryonic fish, but comparisons of the two approaches with species from the Great Lakes are limited. It may be particularly important to examine this issue in the Great Lakes because a relatively young group of post-glacial fish species are present which may be difficult to resolve using morphology or genetics. Six hundred and fifty seven larval fish were identified from Lake Huron (Ontario, Canada), using morphology and DNA barcoding. DNA barcoding was used to identify 103 embryos that morphology could not identify. Morphological identification and DNA barcoding had a percent similarity of 76.9%, 96.6% and 96.6% at the species, genus, and family levels, respectively. Thirty-seven specimens were damaged and unidentifiable using morphology; 35 of these were successfully identified using DNA barcoding. However, 23 other specimens produced no PCR product for barcoding using 2 different primer sets. Discrepancies between morphology and DNA barcoding were driven by two major factors: inability of cytochrome oxidase I to resolve members of the genus Coregonus and limited resolution of morphological features for Catostomus. Both methods have pros and cons; however, DNA barcoding is more cost-effective and efficient for industrial monitoring programs.     

Genetic variation at the mtDNA ND-1 locus among North American wild and hatchery brown trout (Salmo trutta)

Despite extensive knowledge of mitochondrial DNA (mtDNA) variation in European brown trout (Salmo trutta) populations, little is known about their nucleotide sequence variation in North America. The objective of this study was to quantify single nucleotide polymorphisms (SNPs) at the ND-1 mtDNA locus of 62 brown trout from hatcheries in Michigan and Wisconsin as well as Michigan streams and Lake Michigan. We identified 25 SNPs that characterized nine distinct mtDNA haplotypes in the Wild Rose, Gilchrist and Seeforellen brown trout strains. Although most SNPs were represented by synonymous nucleotide substitutions, three individuals of the Seeforellen strain had non-synonymous nucleotide changes. MtDNA haplotypes identified in North American brown trout in this study showed nucleotide similarity at the ND-1 locus to brown trout from northern Europe.     

Acoustic estimates of abundance and distribution of spawning lake trout on Sheboygan Reef in Lake Michigan

Efforts to restore self-sustaining lake trout (Salvelinus namaycush) populations in the Laurentian Great Lakes have had widespread success in Lake Superior; but in other Great Lakes, populations of lake trout are maintained by stocking. Recruitment bottlenecks may be present at a number of stages of the reproduction process. To study eggs and fry, it is necessary to identify spawning locations, which is difficult in deep water. Acoustic sampling can be used to rapidly locate aggregations of fish (like spawning lake trout), describe their distribution, and estimate their abundance. To assess these capabilities for application to lake trout, we conducted an acoustic survey covering 22 km² at Sheboygan Reef, a deep reef ( < 40 m summit) in southern Lake Michigan during fall 2005. Data collected with remotely operated vehicles (ROV) confirmed that fish were large lake trout, that lake trout were 1–2 m above bottom, and that spawning took place over specific habitat. Lake trout density exhibited a high degree of spatial structure (autocorrelation) up to a range of ∼ 190 m, and highest lake trout and egg densities occurred over rough substrates (rubble and cobble) at the shallowest depths sampled (36–42 m). Mean lake trout density in the area surveyed (∼ 2190 ha) was 5.8 fish/ha and the area surveyed contained an estimated 9500–16,000 large lake trout. Spatial aggregation in lake trout densities, similarity of depths and substrates at which high lake trout and egg densities occurred, and relatively low uncertainty in the lake trout density estimate indicate that acoustic sampling can be a useful complement to other sampling tools used in lake trout restoration research.