Spotted sucker (Minytrema melanops) COSEWIC assessment and status report: chapter 6

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Biology

Reproduction

During late spring to early summer, Spotted suckers spawn over clean riffle habitats. Eggs are semi-buoyant and hatch within 7 to 12 days after fertilization (Becker 1983). In Georgia, Spotted suckers were observed to spawn at water temperatures between 12°C and 19°C (McSwain and Gennings 1972). Spawning occurs earlier in the southern portions of its range (i.e. March in Georgia, May in Wisconsin). Spawning groups consisted of three individuals: one female and two males. Observations from Canadian waters have not been reported. Spotted suckers in Missouri reach maturity at age 3 (Pflieger 1975), while dwarf forms captured in Ohio are reported to mature at a length of 150 mm (Trautman 1981). Age at maturity of Canadian populations is not known. A single female in breeding condition collected from the Thames River was aged at five years (Parker and McKee 1984).

Injections of human chorionic gonadotropin (HCG) have induced spawning of captive Spotted Suckerspotted suckers at 18°C (Ludwig 1997).

Survival

Information regarding the demographics of Canadian spotted sucker populations is lacking. At the end of the first growing season in Ohio, young-of-the-year spotted suckers were between 51 and 102 mm in length. Adults were between 229 and 381 mm in length with the largest specimen 450 mm (Trautman 1981). In Oklahoma, spotted suckers attain a length of 155 mm in the first year and average 290 mm (1+), 340 mm (2+), 410 mm (3+) and 440 mm (4+) in successive years (Pflieger 1975). The maximum age reported for U.S. populations is six years (Carlander 1969). Scales from two Canadian specimens (358 mm and 373 mm total length) were aged at 7 and 8 years (McAllister et al. 1985).

Nutrition and interspecific interactions

Adult and juvenile Spotted suckers feed on a variety of prey items such as diatoms, zooplankton, chironomids and molluscs (Pflieger 1975, White and Haag 1977). White and Haag (1977) described ontogenetic shifts in the feeding habits of Kentucky Spotted sucker populations. Larval spotted suckers (12 to 15 mm total length (TL)) fed at the surface and mid-water column on zooplankton and diatoms. At 25 to 30 mm TL, individuals feed over patches of sand and in shallow backwaters of creeks. At approximately 50 mm TL they started feeding on bottom benthic organisms and sand began appearing in the gut. Individuals longer than 50 mm TL had similar feeding habits as the adults. No data on the feeding habits of Great Lakes basin populations are available.

Juvenile spotted sucker are probably preyed upon by piscivorous birds and fish (Parker and McKee 1984).

Parasites of the spotted sucker are identified in Hoffman (1967), Mackiewicz (1968) and Christensen et al. (1982).