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COSEWIC Assessment and Update Status Report on the Blackfin Cisco in Canada

Update
COSEWIC Status Report
on the
blackfin cisco
Coregonus nigripinnis
in Canada
2007

Species Information

Name and Classification

Kingdom:
Animalia
Phylum:
Chordata
Class:
Actinopterygii
Order:
Salmoniformes
Family:
Salmonidae
Subfamily:
Coregoninae
Genus and Species:
Coregonus nigripinnis (Milner 1874)
Common Name
English:
blackfin cisco (Nelson et al. 2004)
French:
cisco à nageoires noires (Scott and Crossman 1973)
Other:
blackfin, black-fin tulibee, black-back tullibee, black-fin, mooneye cisco and bluefin (Scott and Crossman 1973).


The blackfin cisco is one of 10 cisco species found in Canada (Scott and Crossman 1973), one of seven cisco species found in the Great Lakes (Cudmore-Vokey and Crossman 2000), and one of six cisco species identified as an incipient species flock endemic to the Great Lakes by Koelz (1929). These counts exclude the longjaw cisco (C. alpenae), described by Koelz (1929) and included in Scott and Crossman (1973), as it is considered a synonym of shortjaw cisco (C. zenithicus) by Todd et al. (1981).

The blackfin cisco (Coregonus nigripinnis) was originally named by Gill (in Hoy 1872). Hoy’s 1872 paper did not describe the species but gave Gill as the authority for C. nigripinnis. Recent questions on the authority of this species have arisen. Eschmeyer (1998) noted that Hoy or Milner (1874, in Eschmeyer 1998) may be the authority, as Gill’s manuscript was never published (Nelson et al. 2004). Based on additional information from Eschmeyer (1998), Milner’s 1874 paper is presently considered by the AFS as the first valid description of the blackfin cisco (Nelson et al. 2004).


Taxonomy

In terms of its taxonomic nomenclature, especially as related to the Great Lakes basin and to inland waters, blackfin cisco has long been recognized as a problematic species. Koelz (1929) originally recognized four subspecies of C. nigripinnis within the Great Lakes, with each restricted to the following specific lakes: C. n. nigripinnis (lakes Michigan and Huron), C. n. cyanopterus (Lake Superior) and C. n. prognathus (Lake Ontario). However, Koelz (1929) noted difficulty in the ability to distinguish small C. n. nigripinnis and C. n. cyanopterus from C. kiyi (kiyi) in lakes Huron and Superior, respectively. More recently, C. n. cyanopterus in Lake Superior was synonymized with the shortjaw cisco (C. zenithicus) (Clarke and Todd 1980; Todd and Smith 1980; Becker 1983). The Lake Ontario type material of C. n. prognathus was examined by Todd (1981) and considered as a mixture of coregonine species with the holotype considered a nomen dubium. As a result of these findings, no valid forms of blackfin cisco are considered to have occurred in lakes Superior and Ontario.

Outside of the Great Lakes, Koelz (1929) classified one subspecies from Lake Nipigon as C. n. regalis Clarke (1973) and Scott and Crossman (1973) have suggested that these fish were more probably C. artedii; while Nelson et al. (2004) considered the blackfin cisco to be extant in Lake Nipigon. According to recent observations, blackfin cisco are still found in Lake Nipigon (R. Salmon, Ontario Ministry of Natural Resources (OMNR), Nipigon District, Nipigon, ON, personal communication 2003; T. Todd, United States Geological Survey (USGS), Ann Arbour, MI, personal communications 2003, 2005).

The blackfin cisco has been recorded as present in inland lakes across central Canada (Nelson et al. 2004); however, the taxonomic identity of these fish is uncertain. Scott and Crossman (1973) suggested that, “C. nigripinnis is a problem species in inland waters and is most decidedly in need of critical systematic review”, and that the species, “may well prove to be taxonomically inseparable from a broadly redefined C. artedii”. To date, a comprehensive systematic and taxonomic review of the North American ciscoes has not been undertaken. Therefore, there is no formal taxonomic description or authority for the purported blackfin ciscoes reported present in the inland lakes of central Canada (see also Distribution – Canadian Range).

Research on the shortjaw cisco (C. zenithicus) revealed that Great Lakes and inland populations of this species were genetically indistinguishable from the cisco (C. artedii); however, the shortjaw cisco is still considered to be a valid species (Todd et al. 1981, Turgeon et al. 1999, Turgeon and Bernatchez 2003). This may be an indication that some, or all, of the endemic cisco species may actually be ecomorphotypes of the cisco (C. artedii), rather than valid species. If, in future, this was shown to be true for the blackfin cisco, it would still be considered an evolutionarily significant unit (ESU) or, at the very least, a unique morphotype.

Turgeon and Bernatchez (2003) suggested a possible resolution to the taxonomic confusion related to ciscoes, including the blackfin cisco. Based on their work on reticulate evolution and phenotypic diversity in North American ciscoes, Turgeon and Bernatchez (2003) suggested a single taxon, C. artedii (sensu lato), which includes blackfin cisco, be recognized as the sole legitimate taxon for North American ciscoes distributed in central Canada and the northern United States. This suggestion has not gained wide acceptance by others in the field and, at the time of preparing this update status report, the troubling taxonomy of this species remains unresolved and the taxonomy of Koelz (1929) isaccepted by Nelson et al. (2004).


Description

The blackfin cisco was described by Koelz (1929) based on specimens collected in Lake Michigan (the type locality). However, within the Great Lakes, ciscoes as a group are noted to have changed considerably since Koelz’s time, exhibiting morphological variation within, and among, species that currently makes their classification difficult (Todd and Smith 1992). Parallel evolution, hybridization, local adaptation and phenotypic plasticity are believed to have interacted in varying degrees to produce a confounding array of forms and species in the Great Lakes and inland lakes that challenge traditional classification (Todd and Smith 1992; Steinhilber 2002).

As a result of the taxonomic uncertainty related to the blackfin cisco, the following description is based on Great Lakes specimens only (from Scott and Crossman 1973). The blackfin cisco is an elongate, lateral compressed fish whose greatest body depth is found anteriorly (Figure 1). The average adult length is approximately 330 mm and McAllister et al. (1985) reported a maximum length of 510 mm.


Figure 1: Fresh Specimen of a Blackfin Cisco (Coregonus nigripinnis) Caught in the Little Jackfish River in 2004

Figure 1: Fresh specimen of a blackfin cisco (Coregonus nigripinnis) caught in the Little Jackfish River in 2004. Photograph courtesy of David Stanley.

Photograph courtesy of David Stanley.

The head is broadly triangular with a blunt snout and terminal mouth that has the lower jaw usually projecting beyond, or sometimes equal to, the upper jaw. The eyes are large, with a diameter equivalent to about 25% of the head length. The gill rakers are long; the longest gill raker is greater in length than the longest gill filaments. The number of gill rakers ranges from 36-54, depending on geographic location.

A small adipose fin is present, and all other fins are relatively long. The dorsal fin has 9-11 rays. The caudal fin is widely spread and deeply forked. The anal fin has 10‑13 rays, the pelvic fins have 11-12 rays, and the pectoral fins have 15-18 rays. Scales are cycloid and large; the scale count along the lateral line ranges from 74-89 (Scott and Crossman 1973).

The overall colouration of blackfin cisco is dark silvery, with pink or purple iridescence on the sides. The back is dark green to black and silvery below. The upper and lower jaws are whitish but darkly pigmented. All fins are typically heavily pigmented black, particularly on the outer half. Breeding males and some females are described as developing nuptial tubercles or pearl organs during spawning periods.


Designatable Units

All Great Lakes and Lake Nipigon populations described by Koelz (1929) are found within the Great Lakes-Upper St. Lawrence ecozone of the freshwater ecozone classification adopted by COSEWIC. Based on morphological data, Koelz (1929) considered the lakes Huron and Michigan population(s) to be one subspecies (C. n. nigripinnis), and the Lake Nipigon population to consist of a second subspecies (C. n. regalis). Koelz (1929) also described subspecies from Lake Ontario (C. n. prognathus) and Lake Superior (C. n. cyanopterus); however, these forms have been since synonymized with the shortjaw cisco (Clarke and Todd 1980) and deemed invalid (Todd 1981), respectively.

In Ontario, the blackfin cisco has been reported in several lakes, outside of the Great Lakes and Lake Nipigon, in the Great Lakes-Upper St. Lawrence ecozone. However, the taxonomy of the fish in these lakes has not been resolved.

Due to the taxonomic uncertainties described above it is not possible at this time to determine if we are dealing with ecomorphotypes of a common and widespread species (Coregonus artedi), or distinct populations of blackfin cisco (C. nigripinnis). The uncertainty of systematic status can probably only be resolved through a comprehensive taxonomic/systematic review of the sub-genus, and therefore we will consider a single designation for the species.