Status, Distribution, and Conservation of Native Freshwater Fishes of Western North America

ABSTRACT The Lewis and Clark expedition crossed the Continental Divide in 1805 on the way west to the Pacific Ocean. Based on journal entries, members of the expedition probably encountered two species of resident salmonids and four of the six species of anadromous salmonids and steelhead (Family Salmonidae, genus <em>Oncorhynchus</em>). The salmonid species were called common salmon (now known as Chinook salmon <em>O. tshawytscha</em>), red charr (sockeye salmon <em>O. nerka</em>), white salmon trout (coho salmon [also known as silver salmon] <em>O. kisutch</em>), salmon trout (steelhead <em>O. mykiss</em>), and spotted trout (cutthroat trout <em>O. clarkii</em>). There was no evidence of the expedition encountering pink salmon <em>O. gorbuscha</em>, chum salmon <em>O. keta</em>, or species of true char <em>Salvelinus</em> spp. Common fishes procured from Indian tribes living along the lower Columbia River included eulachon <em>Thaleichthys pacificus</em> and white sturgeon <em>Acipenser transmontanus</em>. The identity of three additional resident freshwater species is questionable. Available descriptions suggest that what they called mullet were largescale sucker <em>Catostomus macrocheilus</em>, and that chubb were peamouth <em>Mylocheilus caurinus</em>. The third questionable fish, which they called bottlenose, was probably mountain whitefish <em>Prosopium williamsoni</em>, although there is no evidence that the species was observed in the Columbia River drainage. Missing from the species list were more than 20 other fishes known to Sahaptin-speaking people from the mid-Columbia region. More complete documentation of the icthyofauna of the Pacific Northwest region did not occur until the latter half of the 19th century. However, journals from the Lewis and Clark expedition provide the first documentation of Columbia River fishes.

THE EFFECT OF EXERCISE ON THE CARDIAC OUTPUT AND BLOOD FLOW DISTRIBUTION OF THE LARGESCALE SUCKER CATOSTOMUS MACROCHEILUS

Cardiac output (Q.) and blood flow distribution were measured in adult largescale suckers at rest and while swimming. Cardiac output was directly measured using an ultrasonic flowprobe in fish during the summer (16°C), fall (10°C) and winter (5°C). Largescale suckers were adept at holding station against a current without swimming and, when engaged in this behavior, they did not significantly increase Q. relative to that found in fish in still water. When fish began to swim, Q. increased significantly. From 16 to 10°C, the critical swimming speed (Ucrit), maximum Q. and scope for Q. of the suckers did not change. However, from 10 to 5°C all three traits were significantly reduced. Thus, these fish respond to variation in water temperature in two different ways. From 16 to 10°C, the fish compensate perfectly for the change in temperature with respect to cardiac and swimming performance. From 10 to 5°C, however, largescale suckers experience a dramatic decline in cardiac and swimming performance that may be associated with a quiescent overwintering strategy. Blood flow distribution in the fish at rest and while swimming was measured at 16°C using injection of colored microspheres. In the resting fish, over 10 % of the microspheres were recovered from the kidney and over 43 % were recovered from white muscle. When the fish were swimming, there was a 60-fold increase in blood flow to the red muscle while blood flow to all other tissues remained consistent with that at rest.

Comparative feeding ecology and reproductive performance of ospreys in different habitats of southeastern British Columbia

We compared the general breeding and feeding ecology of ospreys (Pandion haliaetus) in the Creston and Nelson areas of southeastern British Columbia. In the Creston Valley, ospreys nested atop tall trees surrounding a shallow and productive warm-water marsh. Prey species taken by male ospreys included black bullhead (Ictalurus melas), pumpkinseed (Lepomis gibbosus), and yellow perch (Perca flavescens). In contrast, near Nelson, ospreys nested on man-made structures along the narrow West Arm of Kootenay Lake. Osprey prey species in the Nelson area included longnose sucker (Catostomus catostomus), largescale sucker (Catostomus macrocheilus), and mountain whitefish (Prosopium williamsoni). Prey captured at Nelson were larger and contained significantly more energy than at Creston Valley, and hunting from a perch was used for 26% of all captures. All Creston Valley prey were caught by flight hunting. The strike success of foraging ospreys at Nelson was significantly higher than at Creston, and the net yield of flight hunting was 3 times higher. In spite of these differences, the breeding performance of ospreys in the two areas was very similar. Average clutch size was 2.8, brood size at hatching was 2.0, and the average pair fledged 1.4 young. The nest failure rate did not differ between the two areas. Most clutches were initiated in early May, with Nelson-area ospreys laying, on average, 4–7 days later. Egg volumes were smaller at Nelson (66.6 vs. 69.1 cm3). However, the rate at which nestlings gained mass was significantly greater at Nelson. We discuss reasons why the breeding performance varies so little in spite of the great differences in feeding regime.

Myxobolid parasites (Myxozoa: Myxobolidae) infecting fishes of western Montana, with notes on histopathology, seasonality, and intraspecific variation

Cypriniform and salmonid fishes of the Columbia River drainage of western Montana harbor five members of the myxozoan family Myxobolidae. Myxobolus muelleri inhabits Ptychocheilus oregonensis (northern squawfish), Mylocheilus caurinus (peamouth), Richardsonius balteatus (redside shiner), and Catostomus macrocheilus (largescale sucker). Cysts appeared in gills, musculature, subcutis, and visceral mesenteries. Unencysted spores infiltrated mesenteries and viscera. Spore size and shape in the various tissues and hosts were highly varied. Muscle and subcutaneous cysts were associated with connective tissue proliferation and muscle degeneration; cyst rupture was associated with diffuse inflammation and rodlet cell proliferation. Infection prevalence in muscles and kidneys was high in adult and juvenile hosts (78–100%) throughout the year. Seasonal prevalence of gill and subcutaneous infections fluctuated markedly. Cysts of Myxobolus dujardini occurred in gills of the northern squawfish, peamouth, and redside shiner. Unicauda sp. was found in the eye capsule, gall bladder, mesenteries, and kidney of northern squawfish. Henneguya zschokkei occurred in intermuscular connective tissue of Prosopium coulteri (pygmy whitefish) and Prosopium williamsoni (mountain whitefish). Myxobolus sp. occurred in the gills of Catostomus catostomus (longnose sucker).

Protozoan and Metazoan Parasites of Fishes from the Headwaters of the Parsnip and McGregor Rivers, British Columbia: A Study of Possible Parasite Transfaunations

Results are presented of a study to determine the possible extent of parasite transfaunation across the Continental Divide as a result of a proposed water diversion in northeastern British Columbia. Fish populations in the headwater areas of the McGregor River (Pacific drainage) and of the Parsnip River (Arctic drainage) were sampled during August–November 1976 and during June–September 1977. Eighty-eight species or higher taxonomic groups of parasites were recovered from 1489 host specimens, representing 13 genera and 20 species of fishes. Eimeria cotti from Cottus cognatus and Rhabdochona zacconis from Catostomus macrocheilus have not been previously recorded from North America. New Canadian records are Chloromyxum granulosum, C. montschadskii, Leptotheca sp., Myxidium macrocheili, Myxobolus aureatus, M. microthecum, Neomyxobolus ophiocephalus, Unicauda crassicauda, and Wardia sp. Twenty-six parasites show disjunct distributions in the study area. Three forms (Ceratomyxa shasta, Cryptobia salmositica, and Haemogregarina irkalukpiki) are identified as posing the greatest threat to the fisheries resources of the immediate area and also to the downstream areas. Based in part on these studies, the British Columbia Hydro and Power Authority, in a public announcement, suspended engineering studies of the proposed diversion.