Müller's Whitefish

description

Description. Shape: Body elongated and slender. Greatest body depth anterior of dorsal fin. Ventral profile and dorsal profile similar and slightly arched. Dorsal and ventral profile from tip of snout to interorbital mostly straight and then slightly convex to dorsal and pelvic fin origin respectively. Head long. Snout long and tip of snout if often pointed and seldomly fleshy resulting in a not pronounced rostral plate. Mouth long and terminal. Large eye with a subtle sickle cell-shaped (seldom roundish) eye-socket in the historical specimens and a mostly roundish (seldom sickle cell-shaped) eye-socket in the contemporary specimens. The eye of the historical specimens is larger than those of the contemporary specimens. Pectoral fin moderately long and tapered. Anterior unbranched ray of the erected dorsal fin ranges from almost vertically straight to an ~ 70 - 80 ° angle to body axis and only bent slightly posteriorly at end of the ray. Caudal peduncle narrow and elongated with caudal fin forked and sometimes moderately to strongly asymmetrical with often ventral part being longer. Unbranched rays of anal fin straight and rarely bent posteriorly at end of ray. Anal fin longest ant

A taxonomic revision of ten whitefish species from the lakes Lucerne, Sarnen, Sempach and Zug, Switzerland, with descriptions of seven new species (Teleostei, Coregonidae)

diagnosis

Diagnosis. Coregonus muelleri is a small whitefish species (standard length at 3 years of age: range = 160 - 232, mean = 194) with weak pigmentation of all fins and body; pale olive-brown colouration on the flanks above the lateral line; elongate slender body; large eye (eye diameter: 22.2 - 26 % HL, mean = 24.1) with a subtle triangular eye socket; tip of snout pointy; many and long gill rakers (longest gill raker: 12.5 - 16.7 % HL, mean = 14.5; total gill raker number: 33 - 43).

A taxonomic revision of ten whitefish species from the lakes Lucerne, Sarnen, Sempach and Zug, Switzerland, with descriptions of seven new species (Teleostei, Coregonidae)

distribution

Distribution and notes on biology. Coregonus muelleri occurs in all basins of Lake Lucerne (Fig. 2) except for Lake Alpnach (Steinmann 1950; J. Muggli, pers. comm.). Coregonus muelleri was (besides C. nobilis) historically and is today the most abundant and commercially important whitefish species in Lake Lucerne (Birrer and Schweizer 1935; Muggli 2015; Alexander et al. 2017 a). Coregonus muelleri feeds - depending on the time of the year - on different pelagic prey (i. e., variety of zooplankton such as Bythotrephes, Daphnia, Bosmina, Copepoda, Leptodora and rarely Chironomidae) (Birrer and Schweizer 1935). It is a small whitefish species with the size at 3 years of age of C. muelleri being considerably smaller than that of C. litoralis, C. intermundia and C. suspensus (Suppl. material 1: table S 3). We cannot compare its size to C. nobilis since only older individuals of the latter species have been caught (Hudson et al. 2016). It has a slow growth rate (Birrer and Schweizer 1935; Steinmann 1950). Coregonus muelleri has a long spawning season with presumably two spawning peaks. The historical literature suggests that C. muelleri has a spawning peak in the early summer from July t

A taxonomic revision of ten whitefish species from the lakes Lucerne, Sarnen, Sempach and Zug, Switzerland, with descriptions of seven new species (Teleostei, Coregonidae)

etymology

Etymology. The species is named after the late Dr. Rudolf Mueller, a fisheries biologist and former department head and research group leader at EAWAG, Center for Ecology, Evolution and Biogeochemistry (CEEB) in Kastanienbaum, Switzerland. He dedicated a large part of his career to understanding the ecology of whitefish in Swiss lakes, and confirmed the re-discovery of C. nobilis.

A taxonomic revision of ten whitefish species from the lakes Lucerne, Sarnen, Sempach and Zug, Switzerland, with descriptions of seven new species (Teleostei, Coregonidae)