Sculpin (Cottidae)

Figure 1. Mottled Sculpin (Cottus bairdi) in captivity.

Family Cottidae is largely marine in distribution, with the northern Pacific Ocean maintaining the majority of the taxa. In the freshwater systems of North America, two genera and less than 30 species have been identified. Much like the darters (Etheostoma and Percina), sculpins are primarily benthic (see fig. 1) dwelling fishes lacking a swim bladder. They are aggressive predators, feeding chiefly on macroinvertebrates, crayfish, and smaller fishes.

Family Level Identifiers (see Fig. 1):

Head and mouth large.
Body dorsally depressed (see fig. 3).
Often scaleless, although a few ctenoid scales may be present.
Pelvic fin with one spine and two to five rays.
More - tips about genus identification (see below)

Habitat:

Most sculpin species dwell in of areas swift current and considerable groundwater influence (coldwater streams). Although they are often more common in small to moderate-sized streams (see fig. 2), they are also found in rivers and lakes. Favored substrates include gravel, cobble and boulders.

Figure 1:

Figure 1. Mottled Sculpin (Cottus bairdi) frontal view.

Pollution Tolerance:

Figure 2. Small Alabama headwater stream. Habitat of Cottus carolinae.

Pollution tolerance varies among this cool water dwelling family. In general, sculpins are intolerant to moderately tolerant of polluted conditions. Trautman (1981) found that mottled sculpin populations decreased in the presence of silts, pollution and disturbance, and maintained that flourishing populations occured in the clearest and cleanest brooks of higher gradients.

Use in IBI:

Family Cottidae is sometimes used as an alternative taxa in metric 2 (darters), or in conjunction with other benthic taxa such as madtoms or darters. These taxa are generally more vulnerable to stream degradation because they feed and reproduce in benthic habitats (Kuehne and Barbour 1983, Ohio EPA 1987). Their general presence is accounted for in numerous other metrics, such as Metric 5: Number and Identity of Intolerant Species (when applicable) and Metric 1: Total Number of Fish Species.

Table 1. Tolerance designations for selected sculpins
Species Name	Common Name	Pollution Tolerance	Habitat Disturbance
Cottus asper	Prickly sculpin	M	NR
Cottus bairdi	Mottled sculpin	I	NR
Cottus beldingi	Paiute sculpin	I	NR
Cottus carolinae	Banded sculpin	M	I
Cottus cognatus	Slimy sculpin	M	NR
Cottus perplexus	Reticulate sculpin	T	NR
Cottus rhotheus	Torrent sculpin	I	NR
Cottus ricei	Spoonhead sculpin	M	NR
Myoxocephalus thompsoni	Deepwater sculpin	M	NR

Key
Pollution Tolerance	Habitat Disturbance
T = Tolerant	T = Tolerant
M = Intermediate	MT = Moderately Tolerant
I = Intolerant	MI = Moderately Intolerant
NR = No ranking	I = Intolerant
	NR = No ranking

Genus Level Identifiers

Mottled Sculpin (Cottus bairdi)

General things to look for: Cottus is the main genus in the Cottidae family.

Genus Cottus: Depressed head. Large pectoral fins. Many of the identifiers of this genus are internal or beyond the scope of this guide.

Banded Sculpin (Cottus carolinae)