Transport and growth of larval cisco (Coregonus artedi) in the Keweenaw Current region of Lake Superior

Abstract

Larval cisco ( Coregonus artedi ) were sampled from Lake Superior off the western coast of the Keweenaw Peninsula (Michigan, USA) to determine if the Keweenaw Current influences their distribution and growth. Bongo net tows were conducted during April–June 2000 from four transects extending from 0.1 to 17 km offshore. For most sampling dates, cisco tended to be slightly more abundant, larger, and older at inshore locations. Later-hatched larvae appeared at the western-most transects first, during which time earlier-hatched larvae disappeared from the study area. This pattern followed what would be expected if larvae were being transported eastward by the prevailing Keweenaw Current. Estimated growth rates were 84% higher for later-hatched compared with earlier-hatched larvae and 25% lower for offshore larvae from the eastern-most transects compared with elsewhere. Accordingly, surface water temperatures partly explained spatial and temporal variations in growth rate. These results indicate that cisco larvae in Lake Superior may be transported great distances from major spawning sites by longshore currents and that the temperature regime of nursery areas may largely control their growth.