Ichthyomyzon Gagei - Life History

Life History

The southern brook lamprey’s life cycle consists of two main stages: larval and adult. During the larval stage, I. gagei inhabits a distinct micro habitat involving relatively slow moving water and a sandy substrate (Gallaway 1977). The consistency of the substrate is vitally important to the Southern brook lamprey because during the larval stage, I. gagei burrows into the substrate using its oral disk as an anchor (Beamish 1994). I. gagei secretes mucous from its body to form a tube leading to the entrance of the burrow and to provide support for the burrow (Beamish 1994).The formation of this larval burrow relies on the composition and size of the substrate available. The combination of both small and large particles and coarse and fine sand grains allow I. gagei to construct a suitable burrow that allows enough water to flow through the burrow to ensure proper respiration (Beamish 1994). The substrate in which larval I. gagei burrow must not contain too many fine silt and clay particles as this would inhibit respiration while too many particles of coarse sand would hinder proper burrow construction (Beamish 1994). The larval stage is complete after approximately three years (Beamish 1982). Following the larval stage, I. gagei undergoes metamorphosis into the adult form. Adult I. gagei are found in crevices and cracks between large rocks in deeper, faster moving water than the habitat occupied during the larval stage (2012. Minnesota Department of Natural Resources). After completing the metamorphosis to adults, I. gagei come together in groups to spawn and, once spawning is complete, the adults die (Williams 2006). Spawning usually occurs between April and May and takes place in another distinct microhabitat consisting of shallow riffle areas with rocky substrate with a water temperature falling between 17°C to 21°C (Cochran 2000). Fecundity of I. gagei averages between 1,000 to 3,264 oocytes (Beamish 1983). Human factors have been found to influence the available habitat for spawning I. gagei. Southern brook lampreys have been recorded using shallow areas under bridges as spawning grounds possibly to help conceal spawning aggregations from visual predators.