Actinopterygii (ray-finned fishes) > Scorpaeniformes
(Scorpionfishes and flatheads) > Cottidae
Etymology: Cottus: Greek, kottos = a fish (Ref. 45335); asper: asper meaning rough (Ref. 1998).
Environment: milieu / climate zone / depth range / distribution range
Marine; freshwater; brackish; demersal; catadromous (Ref. 51243). Temperate; 60°N - 32°N
North America: Pacific slope drainages from Seward, Alaska to Ventura River, California, USA; also east of Continental Divide in upper Peace River in British Columbia, Canada. Exhibits coastal and inland forms that are genetically distinct (Ref. 27547).
Size / Weight / Age
Maturity: Lm ?  range ? - ? cm
Max length : 30.0 cm TL male/unsexed; (Ref. 5723); common length : 7.0 cm TL male/unsexed; (Ref. 12193); max. reported age: 7 years (Ref. 28210)
(total): 7 - 10;
soft rays: 15 - 19;
Vertebrae: 34 - 39. Distinguished by a complete lateral line, a single pore at the tip of the chin, the presence of 15 to 19 anal rays, and well developed palatine teeth (Ref. 27547). Pectorals large and fan-shaped; caudal truncate or slightly rounded (Ref. 27547). Dark brown, olive or gray above and on sides, whitish yellow to white below; usually three dark irregular blotches or bars below soft dorsal; vague irregular dark mark on sides; fins (except anal) have dark bars, the first dorsal with a dark spot towards the rear (Ref. 27547). Both sexes show an orange band on the edge of the first dorsal fin at spawning time (Ref. 27547). The inland form is generally more densely prickled over a larger portion of the body while the coastal form shows a reduced number of prickles (Ref. 28211).
There appears to be two genetically distinct forms (Ref. 27547), an inland form found in sandy and rocky shores of lakes, and a coastal form usually found over sand in quiet runs of small to medium rivers; sometimes in salt water near river mouths (Ref. 2850). The coastal form moves into brackish estuaries to spawn (Ref. 27547). Oviparous with demersal, adhesive eggs and pelagic larvae (Ref. 265). Feed mainly on aquatic insect larvae and bottom invertebrates (Ref. 1998). Too small to be used as food and too difficult to capture in large numbers to be used for anything else (Ref. 27547) but large individuals are reported to be excellent eating as well as good bait fishes (Ref. 2850).
Prior to breeding, males move downstream and select a nesting site under boulders or flat rocks. Females aggregate some distance upstream and move down singly to the spawning area. Courtship behavior occurs outside the nest until a female is selected. The pair enter the nesting site, courting continues until eggs are deposited and fertilized. The female then leaves the nest and goes back upstream to feed, while the male spawns with other females or fans and guards the eggs. The male does not feed until the eggs have hatched, moving upstream only in the late summer (Ref. 1998, 27547). During the planktonic stage, larvae of the freshwater nonanadromous form in lakes show distinct diurnal vertical migrations, being most abundant at the surface during the darkest hours of the night. They apparently stay deep in the water during the day and on bright moonlight nights (Ref. 28920). Metamorphosis is complete by the end of the planktonic period and the young take up a demersal mode of life. The young coastal form may move upstream during the fall, although the young may remain in the estuary for a full year (Ref. 27547).
Page, L.M. and B.M. Burr, 1991. A field guide to freshwater fishes of North America north of Mexico. Houghton Mifflin Company, Boston. 432 p. (Ref. 5723)
IUCN Red List Status (Ref. 119314)
CITES (Ref. 115941)
Threat to humans
Aquarium: public aquariums; bait: occasionally
ReferencesAquacultureAquaculture profileStrainsGeneticsAllele frequenciesHeritabilityDiseasesProcessingMass conversion
Estimates of some properties based on models
Phylogenetic diversity index (Ref. 82805
= 0.5000 [Uniqueness, from 0.5 = low to 2.0 = high].
Bayesian length-weight: a=0.00759 (0.00341 - 0.01686), b=3.11 (2.92 - 3.30), in cm Total Length, based on LWR estimates for this (Sub)family-body shape (Ref. 93245
Trophic Level (Ref. 69278
): 3.2 ±0.0 se; Based on diet studies.
Resilience (Ref. 69278
): Medium, minimum population doubling time 1.4 - 4.4 years (tmax=7; Fec=280).
Vulnerability (Ref. 59153
): Moderate to high vulnerability (51 of 100) .