The present-day distributions of 117 native freshwater fishes in Ontario have been shaped by processes active following the Wisconsinan glacial period, 80 000–10 000 years before present. During this glacial period, these species survived in unglaciated réfugia. To understand the processes that resulted in the recolonization of Ontario by fishes following the last glacial period, the refugial areas occupied by each species were determined using a refugial index, and glacial water bodies used as dispersal routes were identified. The refugial origins of the Ontario populations of 91 species were resolved. Seventy-two species resided in the Mississippian refugium, 13 species in the Atlantic Coastal refugium, 4 species in dual Atlantic Coastal – Mississippian refugia, 1 species in a Missourian refugium, and 1 species in Atlantic Coastal, Mississippian, and Missourian refugia. These conclusions differed significantly from those of other studies. Five general patterns were identified from the distributions of 104 species. In addition, there are 13 species that do not fit any of the general patterns. Most species with similar distributions in Ontario shared the same refugia and dispersal routes in eastern North America, therefore it is hypothesized that historical processes were important in shaping the present-day distributions of Ontario freshwater fishes.
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, producing either large‐, medium‐, or small‐bodied fish (ranging from 140 to 127 cm, 126 to 114 cm, and 113 to 102 cm and smaller, respectively). We describe and categorize growth and growth potential to establish standards for detecting change in exploitation and for reviewing minimum size limits (currently underway) based on growth biology to help sustain and even increase the size of muskellunge populations while producing high‐quality trophy fisheries.
The introduction of fishes into North America began in the late 1600's. The number of species has increased over the years, with pulses in the late 1800's and following the 1950's. By 1989, there were 45 established exotic fishes in the continental USA, and 16 in Canada. By 1989, the number brought into, invading, or transferred within Canada was 92 species plus 13 subspecies and hybrids. A special situation for Canada is the steady invasion from U.S. waters. Over the years, 38 such species have been identified. A variety of societal pressures led to the introductions, and the species introduced represent a number of realized or potential environmental impacts. Various international, national, state and provincial agencies or programmes have developed to investigate introductions and/or judge individual applications for the importation or transfer of live fishes. The number and nature of species being moved is still not well known. For Canada, 125 forms (species, hybrids, selected strains) which fit the new definition of Introduced are summarized by province and mode of introduction.
During laboratory and field experiments in Ontario, with hatchery muskellunge 90–235 mm in total length, total removal of a fin did not add to the immediate mortality caused by seining the fish from ponds. The use of an anesthetic during surgery (MS‐222) did not affect subsequent survival of marked, stocked fish. Removal of any single paired fin was equally detrimental to short‐term (3 months) survival. In contrast, over long periods (10 months) the loss of a pectoral fin was more detrimental than loss of a pelvic fin. Removal of both fins of a pair may cause higher mortality than the removal of one fin. Neither the fin removed nor the anesthetic significantly affected short‐term or long‐term growth. Within 1 year of marking regeneration of amputated fins was such that recognition of marked fish was difficult and the degree of difficulty increased with time. Estimates based on marked 2‐year‐old or older individuals could result in substantial underestimates of survival.
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