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.Résumé : Nous avons échantillonné des larves de ciscos de lac (Coregonus artedi) du lac Supérieur au large de la côte occidentale de la péninsule de Keweenaw (Michigan, É .-U.) afin de déterminer si le courant de Keweenaw affecte leur répartition et leur croissance. Nous avons effectué des traits de filets bongo en avril-juin 2000 sur quatre transects allant de 0,1 à 17 km de la rive. Pour la plupart des dates d'échantillonnage, les ciscos avaient tendance à être légèrement plus abondants, plus grands et plus vieux dans les sites près de la rive. Les larves à éclosion plus tardive apparaissent d'abord dans le transect situé le plus à l'ouest, au moment où les larves à éclosion plus hâtive ont disparu de la zone d'étude. Ce patron s'accorde avec ce qu'on peut attendre si les larves sont transportées vers l'est par le courant prédominant de Keweenaw. Les taux de croissance estimés chez les larves à éclosion tardive sont 84 % plus élevés que ceux des larves à éclosion hâtive et ils sont de 25 % inférieurs chez les larves du large dans le transect le plus à l'est par comparaison à tous les autres sites. En conséquence, les températures des eaux superficielles expliquent en partie les variations spatiales et temporelles des taux de croissance. Nos résultats indiquent que les larves de ciscos du lac Supérieur peuvent être transportées sur de longues distances à partir des principaux sites de fraye par les courants côtiers et que les régimes thermiques des zones de nourricerie peuvent en grande mesure contrôler leur croissance.[Traduit par la Rédaction]

Describing historical habitat use of a native fish—Cisco (Coregonus artedi)—in Lake Michigan between 1930 and 1932

“…Managers are evaluating whether extant ciscoes in Lake Michigan will continue to expand and diversify or if other management actions are needed to increase both the abundance and diversification of ciscoes to enhance their recovery and long-term stability [16]. Broadly speaking, habitat uses of cisco for spawning and at larval and juvenile stages remain poorly understood in Lake Michigan and in the other Great Lakes, although Oyadomari and Auer [76] described the habitat use of larval ciscoes in Lake Superior. A more complete description and understanding for habitat use of cisco at each life stage would reveal whether the Lake Michigan ecosystem can still provide habitat connectivity through ontogeny and sustain abundant cisco populations in key historical regions, such as Green Bay.…”

Mercury bioaccumulation in relation to changing physicochemical and ecological factors across a large and undisturbed boreal watershed

“…Riverine larval Cisco are then passively transported downstream shortly after ice break up (Ochman & Dodson, 1982). Similar transportation of larvae shortly after hatch by water currents has been documented in Lake Superior by Oyadomari & Auer (2008). Larval Cisco appear to be tolerant of a wide range of salinities, and have been observed at salinities of 4 parts per thousand or less (Ochman & Dodson, 1982), and up to 15 parts per thousand in Hudson Bay (Ponton, Gagne, & Fortier, 1993).…”

Spatio-temporal trends in the food habits of age-0 lake whitefish

“…Larval lake whitefish are larger (12-13 mm) than larval yellow perch (4.7-6.6 mm) at the time of hatching (Auer, 1982) and may be less susceptible to hydrodynamic transport. However, Oyadomari and Auer (2008) found evidence of hydrodynamic transport in lake cisco (Coregonus artedi) in Lake Superior which have larvae similar in size to lake whitefish. They found that larval lake cisco transported offshore had slower growth than those retained in the warmer coastal water, so it is likely that larval lake whitefish grow and survive better if they are transported to and then retained in bays.…”