Fourhorn sculpin COSEWIC assessment and status report: chapter 3

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Species Information

Name and classification

The fourhorn sculpin, Myoxocephalus quadricornis(Linnaeus 1758), is mainly a marine sculpin with a circumpolar distribution (McAllister 1980). The species is closely related to the lake-dwelling deepwater sculpin, M. thompsoni (Girard 1852), and was originally described from the Baltic Sea. The taxonomy has been the subject of several taxonomic and zoogeographic studies, particularly with regards to the marine fourhorn sculpin and the freshwater deepwater sculpin (Berg 1949; Walters 1955; McAllister 1961; Johnson 1964; McAllister and Aniskowicz 1976). Girard (1852) described the deepwater sculpin from Lake Ontario as Triglopsis thompsoni, and when McAllister (1961) reviewed the earlier history of the problem he considered the fourhorn sculpin to be a separate species and the ancestral form.

Despite the findings of McAllister (1961), other authors felt that the fourhorn and deepwater sculpins were subspecifically related based on the discovery of distinct populations in three lakes on Victoria Island, NU, that possess some intermediate morphological characteristics (Johnson 1964; McPhail and Lindsey 1970). For this reason, McPhail and Lindsey (1970) followed Nikolsky (1961) and Hubbs and Lagler (1964) in considering that the deepwater sculpin was only subspecifically different from the marine fourhorn sculpin. Based on this relation, they recognized the marine form as M. quadricornis quadricornis(Linnaeus) and the freshwater form as M. quadricornis thompsoni (Girard).

McAllister and co-workers (McAllister 1961; McAllister and Aniskowicz 1976; McAllister et al. 1978) examined specimens of both forms and the recently discovered postglacial Arctic freshwater relicts that have been described (McAllister 1961; Hubbs and Lagler 1964; Johnson 1964; McPhail and Lindsey 1970; Dadswell 1972). They considered the two as distinct species based on morphological characteristics, distribution, and ecology. The postglacial Arctic relicts, the focus of this report, fall within the definitions of M. quadricornis and should be commonly referred to as fourhorn sculpin. Nelson (pers. comm., 2002) stated that the marine and freshwater forms of M. quadricornis will be listed as specifically distinct from M. thompsoni in the new edition of “Common and scientific names of fishes of the United States, Canada, and Mexico” scheduled to be published later this year.

Since being originally described by Linnaeus in 1758, the fourhorn sculpin has been subjected to various changes in nomenclature and classification. It has been included in Cottus, Oncocottus, Myoxocephalus, and Triglopsis based on morphological characters (McPhail and Lindsey 1970; Scott and Scott 1988; Muus et al. 1999; Kallner and Bernander 2001). M. quadricornis appears to be the most widely used name by researchers, but Triglopsis has been used in Europe after the cottid was affiliated with that genus by Fedorov (1986). Some scientists recognize the fourhorn sculpin asT. polaris (Khlebovich 1997). Despite the debate over generic affiliation, the higher classification has remained virtually unchanged: Family Cottidae, Suborder Cottoidei, Order Scorpaeniformes, Superorder Actinopterygii, Infraclass Teleostei, Subclass Neopterygii, Superclass Osteichthyes, Subphylum Vertebrata, Phylum Chordata, and Kingdom Animalia.

Due to its circumpolar distribution, the fourhorn sculpin is resident to a number of North American and European countries. The common names utilized in these countries appear in Table 1. The French commonly refer to the fourhorn sculpin aschaboisseau à quatre cornes.

In Inuktitut, the degree of specificity or precision in the correspondence of common names with their taxonomic level, such as species or family, varies according to the subject’s food or other interest. For example, chars are regularly used as food and the Inuit accord them not only individual names for each species, but also, in the case of Arctic char, separate names for the marine form (iqalukpik), the small land-locked form (nutilliq), and the bright red spawning phase (ivitaaruq). This does not seem to apply in the case of sculpins. Several species of the family, to which the Inuit resorted for food in times of famine, are in most localities lumped together under only one name – kanayok (McAllister et al. 1987).

Table 1. The common names, with countries of origin, for Myoxocephalus quadricornis (Linnaeus, 1758)

Description

The freshwater fourhorn sculpin is a relatively small, benthic cottid, rarely reaching a length greater than 100 mm (Bengtsson and Bengtsson 1983; Muus and Dahlstrøm 1999). See Figure 1. Garrow Lake individuals tend to grow larger with upper lengths of 170-194 mm and a recorded range of 20-194 mm (BC Research 1978; Fallis et al. 1987). Fallis et al. (1987) reported a mean of 155 mm total length (TL) and 26.6 g (10-45 g) from 51 individuals collected. The marine form of the species can be easily distinguished from other cottids by the presence of four long, club-like protuberances (frontal and parietal spines) on the head (Scott and Scott 1988; Coad et al. 1995), giving rise to its name. However, these are typically reduced or absent in the freshwater form. Leger (pers. comm., 2003), in describing the Garrow Lake fourhorn sculpin, commented that the horns were soft and very delicate compared to the large, sturdy horns of the marine form. The fourhorn sculpin has four well-developed preopercular spines as well as nasal and cleithral spines. The upper preopercular spine, a simple straight point, is distinctive (Coad et al. 1995).

The body is elongate with a slender caudal peduncle. The head is flattened and wide with close-set eyes on the top of the head. The mouth is terminal with the lower jaw projecting slightly. The vomer in the roof of the mouth bears teeth, but palatine teeth are distinctly absent. Unlike its close relatives there are no folds on the lower flanks. There are two dorsal fins, the first being smaller and spiny; the caudal fin is square or truncate; the anal is soft-rayed and has a long base; the pelvics are small, located well forward beneath the pectorals and have one spine and 3 to 4 soft rays; the soft-rayed pectorals are large and fanlike (see McAllister 1961; Scott and Scott 1988; Coad et al. 1995).

Figure 1. Drawing of the fourhorn sculpin, Myoxocephalus quadricornis (Drawing courtesy of Donald McPhail, University of British Columbia).

These fish lack true scales and may have tubercles (sometimes described as large disklike scales), which can be reduced to prickles, above and below the distinct chainlike lateral line that seldom extends posteriorly past the insertion of the second dorsal fin (McAllister 1961). The second dorsal fin is usually larger in mature males than in the female and the pelvics are notably larger. There may be tubercles on the second dorsal and pectoral fins of males that are not found on females (McAllister 1961; McPhail and Lindsey 1970).

The overall colouration is dark grey to brown, the back being darker, becoming lighter along the sides and light ventrally. The back and sides may be speckled or mottled and there are usually four to seven diffuse, saddle-like bands along the back and sides. The pectoral fins may have up to three diffuse darker bands, the pelvics may be spotted, and the dorsal and anal fins blotched. The caudal fin usually shows dark brown mottling. Males develop a rosy colouration under the head, on the lower pectoral fin, and on the anal and pelvic fins (McAllister 1961; Scott and Scott 1988).

McAllister and Aniskowicz (1976) found that fourhorn sculpins from marine, brackish, and freshwater locations had mean vertebral counts of 38-42 with freshwater specimens being smaller and having fewer vertebrae. Fallis et al. (1987) reported that the vertebral counts of Garrow Lake individuals ranged from 41-43 with a mean of 42.2.

The fourhorn sculpin appears in the important regional ichthyofaunal compendia of Canadian waters: “Atlantic Fishes of Canada” by Scott and Scott (1988, pp. 504-505); “Encyclopedia of Canadian Fishes” by Coad et al. (1995, pp. 295-296); “The Freshwater Fishes of Alaska” by Morrow (1980, pp. 207-209); “Atlas of North American Freshwater Fishes” by Lee et al. (1980, pp. 826); and also in “Fishes of the North-eastern Atlantic and the Mediterranean” by Whitehead et al. (1986, pp. 1259-1260). The freshwater form described in “Freshwater Fishes of Canada” by Scott and Crossman (1973, pp. 842-847) and “Freshwater Fishes of Northwestern Canada and Alaska” by McPhail and Lindsey (1970, pp. 318-323) is the deepwater sculpin, M. thompsoni.

There are approximately 300 species of sculpin, mostly marine but sometimes freshwater, with a few of the marine forms entering rivers and on occasion moving considerable distances upstream. Only three freshwater species, the deepwater sculpin, the slimy sculpin (Cottus cognatus), and the spoonhead sculpin (C. ricei), overlap the distributional range of the fourhorn sculpin (Lee et al., 1980; Morrow 1980; Page and Burr 1991). The aforementioned distinctive characteristics of the freshwater fourhorn sculpin, as well as its restrictive habitat, should allow it to be relatively easy to identify when captured in high Arctic lakes. However, identification may be difficult when distinguishing between the fourhorn sculpin and the deepwater sculpin as the two species closely resemble one another. The deepwater sculpin, as its name implies, inhabits the bottoms of deep, cold lakes up to a depth of 366 m. This cottid, protected in Canada as a threatened species, differs from the fourhorn sculpin usually in the absence of the four horns on the top of the head, and the absence of tubercles below the lateral line (Morrow 1980; Page and Burr 1991). If head spines are present, they are not club-shaped as in the fourhorn sculpin. A maximum length of 230 mm has been recorded for Lake Ontario individuals; however, these are now extripated. Deepwater sculpins now achieve total lengths of 102 to 127 mm (Delisle and Van Vliet 1968).