Academic journal article The American Midland Naturalist

Distribution and Abundance of Slimy Sculpin (Cottus Cognatus) on Prince Edward Island, Canada

Academic journal article The American Midland Naturalist

Distribution and Abundance of Slimy Sculpin (Cottus Cognatus) on Prince Edward Island, Canada

Article excerpt

ABSTRACT.-

Slimy sculpin (Cottus cognatus) are found throughout much of North America; however, their presence has never been recorded on Prince Edward Island (PEI), Canada. After slimy sculpin were discovered in one river in western PEI (Big Pierre Jacques River), all of the rivers on PEI were sampled to determine their distribution. Sculpin were discovered in one additional watershed, the Brae River, which is separated from the Big Pierre Jacques by one watershed. In both rivers, all age classes of sculpin were present, indicating a healthy population. As there are no historical records of slimy sculpin in the province, it is not known whether these fish were introduced to the area, or whether they were historically present but were extirpated from other rivers across the province.

INTRODUCTION

Slimy sculpin (Cottus cognatus Richardson) are found throughout northern North America from Alaska to Labrador, as well as northeastern Siberia. Their distribution in Atlantic Canada was thought to be limited to New Brunswick, with no published records in Nova Scotia, Newfoundland or Prince Edward Island (PEI) (Scott and Oossman, 1998). There is one anecdotal record of a few sculpin being collected in the Big Pierre Jacques River in western PEI after a pesticide-related fish kill in July 1994 (T. Currie, Department of Fisheries and Oceans Maritimes Region, Moncton, NB, pers. comm.); however, this observation was not published. The abundance of sculpin in this river, or their presence elsewhere on PEI, has not been investigated. The objective of this study was to determine the distribution and abundance of slimy sculpin on Prince Edward Island.

METHODS

As part of a more comprehensive study to assess fish communities on PEI, all waterways that were greater than l m in width were sampled on at least one site, unless sections of the river were impounded by beaver dams making sampling impractical due to deep water. There were 130 sites on 76 different rivers sampled (Fig. 1), with up to three sites per river. Rivers adjacent to where slimy sculpin were located were sampled more extensively. Streams varied in width from l m to 15 m, but the total sampling area for each site was approximately 100 m^sup 2^. Barrier nets were placed at the upstream and downstream boundaries of each site to prevent the escape of fish from the study area during sampling. Sites were electrofished with a Smith-Root backpack electrofishing unit, Model 12 POW (Programmable Output Waveform). Three consecutive sweeps of the sampling area were performed, working upstream, with one person electrofishing and two others capturing stunned fish with dipnets. Sampling fish in three sweeps permitted the determination of population estimates, probability of capture (usually between 80-99%) and 90% confidence limits using the program POPDN3, version 1.3 (1985). Fish from each sweep were kept separate from one another in 40-50 liter tubs. Upon completion of electrofishing, fish were anaesthetized with clove oil (2.5 × 10^sup -2^ ml/liter; e.g., Anderson et al., 1997; Keene et al., 1998), identified to species, measured (tip of rostrum to end of tail; ±0.1 cm) and weighed (±0.1 g). Occasionally, if a suitable site could not be found on the river, a few areas on the river were Aspotchecked@. In such cases, the site was not sectioned off, but all fish were captured and identified to species before being released. For these sites, population density estimates were not possible. Water temperature and dissolved oxygen levels were determined at all sites.

RESULTS AND DISCUSSION

Slimy sculpin were found in only two of the rivers (four of the sites) examined - the Big Pierre Jacques River and the Brae River (see stars, Fig. 1). Both of these rivers are in western PEI, and the two watersheds are separated by almost 10 km of salt water, as well as one major watershed (Little Pierre Jacques River) and two smaller watersheds (Dog Creek and MacLean's Brook). …

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