E. J. Crossman

Taxonomy and distribution

This is a family of freshwater fish distributed throughout the world in the Northern Hemisphere (section 1.4). The general body form is long, and subcylindrical in the young and smaller species but laterally compressed and deep bodied in older representatives of the larger species. The head is characterized by a long, flattened snout, large gape, mouth well armed with teeth on jaws, vomer, palatines and tongue. The eyes are moderately large, as is typical in shallow-water sight predators. The unpaired fins (dorsal, caudal and anal) are concentrated at the rear as an adaptation to sprint predation, usually, but not always, on other fish and other vertebrates. The caudal fin is forked, and the paired fins are not large. Nelson (1994) summarized characters of the family as follows: caudal fin with 40 to 50 rays, 17 (rarely 16) branched; infraorbital sensory canal with eight or more pores, nasal bones present, branchiostegal rays 10 to 20, vertebrae 43 to 67. The gill rakers are reduced to patches of small, very sharp denticles. The lateral line is complete and straight, all scales are cycloid, but scales on the lateral line, and elsewhere on some species, are characteristically notched or heart-shaped (cardioid). Maximum size (muskellunge, Esox masquinongy) approximately 165 cm. Maximum age in that species in excess of 30 years, and maximum weight approaching 32 kg, but the smallest species (redfin pickerel, E. americanus americanus) not exceeding 330 mm length, 200 g weight and 8 years of age.

Karyotypes and DNA values for members of the suborder Esocoidei (Osteichthyes: Salmoniformes)

Karyotypes prepared from tissues of gills, gonads, fins, liver, and spleen, yielded the following diploid numbers: all Esox spp. 50, all Umbra spp. (excluding U. krameri) 22, Novumbra hubbsi 48, Dallia pectoralis 78. DNA measurements from Feulgen stain content of erythrocytes, indicated that the species could be divided into two categories: 30–39% of human-Esox spp., Dallia pectoralis, Novumbra hubbsi: 70% of human-Umbra spp. Chromosomal polymorphism was not observed among the various tissues examined nor was it observed among specimens from different habitats. Both the karyotypes and the DNA values indicated that the present tendency to combine the genera Umbra, Novumbra, and Dallia in the single family Umbridae may be ill advised.

Displacement, and home range movements of muskellunge determined by ultrasonic tracking

SynopsisFive adult or subadult muskellunge, Esox masquinongy (Salmoniformes: Esocoidei), were tracked over periods of 6–11 days by means of ultrasonic (74 ± 1 Khz) transmitters, surgically implanted in the body cavity. One of these fish demonstrated that survival and well-being for over a year is probable. There was no apparent effect on equilibrium, swimming, or feeding. There was also no apparent abnormally high amount of movement immediately after release.Signal range was at times no greater than 10 m (in contrast to a potential of 1 km) as a result of the air in the dense aquatic vegetation.Area occupied by a single individual for a protracted period could be described as a linear distance of 300–800 m in the stream, or a circle 300 m in diamter in the lake. Displaced individuals returned to a specific locality. Following spawning they do so over a distance as great as 6.4 km in a maximum of two days. There was evidence that two individuals used the same general area simultaneously.Subsequent results with some of the same individuals indicated that radio transmitters are more practical and yield better results in the situation under study.

Growth and Ultimate Length of Muskellunge from Ontario Water Bodies

Abstract Growth of muskellunge Esox masquinongy from 12 Ontario sources was investigated by examining 582 samples from the Cleithrum Project archive and other specific studies; 88% of the samples were from angler-caught “trophy” fish. We detail sampling problems and develop methods for resolving them. Muskellunge from some sources were unsexed; sex was discriminated (probability of correct classification, 98.3%) from the von Bertalanffy growth parameters ultimate length (L∞) and growth coefficient, K. When one sex was inadequately sampled, the von Bertalanffy growth parameters of one sex were used to estimate those of the other. When samples were small and inadequate (<11), we used concordance sum of squares to match growth and give an interim estimate from the adequately sampled source with the best growth match. In Ontario populations, mean ultimate total lengths range widely: from 81.4 to 140.0 cm for females and from 70.7 to 115.9 cm for males. Females can be grouped into three types of growth, produc...

An apparatus for sampling gut contents of large, living fishes

SynopsisApparatus and methods are described and illustrated for flushing and retaining gut contents from large, living fishes with water supplied by a 12 volt portable pump.

BIODIVERSITY OF THE FISHES OF THE LAURENTIAN GREAT LAKES : A GREAT LAKES FISHERY COMMISSION PROJECT

Abstract The fishes of the Laurentian Great Lakes have been studied and managed with various philosophies involving single species, groups of species, and ecosystems. Only recently has the emphasis shifted to a concern for biodiversity. Biodiversity has been strongly effected by habitat change, loss of indigenous species, introductions, contaminants, and changes in societal attitudes to ‘conservation’ and resource partitioning. At present there are approximately 153 established species in the lakes (not the basin). Of that total, 124 are indigenous, and 30 are naturalized. The number of species now known to have been introduced into the lakes is 57. Introductions result from authorized and unauthorized vectors. Introductions serve to indicate only one of the many impacts. In 1955 the binational Great Lakes Fishery Commission established a three‐year study entitled ‘The Role of Biodiversity in the Management of the Fishes of the Great Lakes’. The objectives of the study were the elucidation, for fishes, of...