Morphology and life history of the Great Slave Lake ciscoes (Salmoniformes: Coregonidae)

Abstract

-The taxonomy of the North American ciscoes (Salmoniformes: Coregonidae) remains unresolved. We provide the first comprehensive description of the Great Slave Lake ciscoes. Our analysis supports the hypothesis that the Great Slave Lake cisco complex includes at least two nominate species (Coregonus artedi and Coregonus sardinella) and an adfluvial C. artedi morph that is distinct from its lacustrine conspecific in terms of life history, morphology, age, growth and mortality. Coregonus sardinella has previously been identified from Great Slave Lake, but we provide the first comprehensive description of this species in the lake and confirm a significant range extension for the species. The lacustrine C. artedi differs little from descriptions throughout its range. In addition to these three ciscoes, linear phenotypic traits, gillraker number and morphology, and growth data support the possible occurrence of two other, less-distinct morphs, the big-eye cisco and a shortjaw-like morph Coregonus zenithicus. Although the big-eye morph was not identified by body shape and linear phenotypic measures, it was visually identified on the basis of differences in traditional phenotypic proportions, such as orbital length, paired fin lengths, head and gillraker morphology expressed as thousands of standard length and showed different age and growth structure compared with the other lacustrine cisco morphs. Coregonus zenithicus was distinguished visually and by a statistical model of linear phenotypic traits as well as by gillraker number and morphology. Identifying, characterising and managing locally adapted cisco morphs that reflect important ecological and bioenergetic linkages are critical to conserving the ecological integrity of northern ecosystems.

Evolution and diversity of two cisco forms in an outlet of glacial Lake Algonquin

“…Given the lack of formal comparison between forms in the Fossmill outlet, and in order to inform comparisons based on genomics, we begin by comparing the morphology of ciscoes captured in benthic and pelagic habitats in lakes of the Fossmill outlet (and in L. Nipigon as reference). We expected to detect two sympatric forms differentiated by habitat, gill-raker counts (Etnier & Skelton, 2003;Häkli, Østbye, Kahilainen, Amundsen, & Praebel, 2017), as well as linear traits and body shape often different between other fish ecotypes (Laporte, Dalziel, Martin, & Bernatchez, 2016;Muir, Vecsei, Power, Krueger, & Reist, 2014;Muir et al, 2013;Perreault-Payette et al, 2017). Our study could identify relict fish populations of major conservation importance given the recent interest in restoring the deepwater fish fauna of the Great Lakes.…”

“…We expected to detect two sympatric forms differentiated by habitat, gill-raker counts (Etnier & Skelton, 2003;Häkli, Østbye, Kahilainen, Amundsen, & Praebel, 2017), as well as linear traits and body shape often different between other fish ecotypes (Laporte, Dalziel, Martin, & Bernatchez, 2016;Muir, Vecsei, Power, Krueger, & Reist, 2014;Muir et al, 2013;Perreault-Payette et al, 2017). Hence, this "in situ" hypothesis predicts that sympatric cisco and blackfin forms would form a genetic cluster in each lake.…”

Morphological and genetic variation in Cisco (Coregonus artedi) and Shortjaw Cisco (C. zenithicus): multiple origins of Shortjaw Cisco in inland lakes require a lake-specific conservation approach

“…Study lakes varied in surface area (4-82,097 km 2 ) and maximum depth (9-614 m). Cisco were sampled as described in Pratt (2012), Howland et al (2013), Muir et al (2013b) and Sandstrom et al (2013). Individuals were classified as SJ or LC based on external morphology (primarily jaw and gill raker characteristics) and conformance to Great Lakes taxonomic definitions (Koelz 1929;Hubbs and Lagler 2007).…”

“…Other species and MTs occur in Great Slave Lake, Lake Nipigon and Lake Superior (e.g. Koelz 1929;Turgeon et al 1999;Muir et al 2013b) but were not considered in this study. With few exceptions, the same fish were used for genetic and morphological analyses (Table S1), but there were no morphological measurements available for Churchill River.…”

“…Given the wealth of past and current effort to define and update the description of this taxon (e.g. Clarke 1973;Todd and Steinhilber 2002;Muir et al 2013b), there will likely be resistance to dismiss it. Second, given the idiosyncratic nature of each instance of divergence across the range, lake-specific Shortjaw DUs will likely be based on a unique combination of evidence for morphological, life history, ecological or genetic distinctiveness.…”