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COSEWIC Assessment and Update Status Report on the Banded Killifish, Newfoundland population in Canada

Limiting Factors and Threats

There are two limiting factors to be considered with respect to Banded Killifish populations in Newfoundland. These are forestry activity (or any other potential anthropogenic disturbance) and the potential impacts of forestry on freshwater watersheds inhabited by this species, and obstacles, such as steep river gradients and physical barriers, preventing inland migration and access to additional suitable habitat.

While little in the way of clear cutting is occurring on the west coast in the area around Banded Killifish populations (H. Smith, pers. comm.), much of the area surrounding several lakes in the Indian Bay watershed, particularly around Fourth Pond, directly connected to Third Pond, one of the lakes containing Banded Killifish, has been or is planned to be clear cut over the next 5 years (M. Wells, pers. comm.). Wells (2002) indicated statistically significant sediment accumulation increase for a 20 m buffer with selective harvesting within the Indian Bay watershed along a headwater stream (p=0.0172 for sediment > 1mm in diameter, 4-fold increase, p=0.0001 for sediment < 1mm in diameter, 5-fold). The effects of such increased suspended sediments include reductions in invertebrate abundances, decreased feeding success for sight feeding species, and dislocation and mortality of early life stages (Miller 1981). Sediments can also abrade and suffocate periphyton and macrophytes thus decreasing the primary production (Waters 1995). Desgagne and Lalancette (1984) indicated that Banded Killifish feed based on visual perception and as Richardson (1939) stated Banded Killifish make use of macrophytes in their reproductive cycle. Therefore these developments may have a severe impact on Banded Killifish populations in Indian Bay should this phenomenon occur throughout the watershed.

Despite the broadened distribution since the previous status report, the newest records are coastal in nature, likely confirming that migration inland is restricted by steep river gradients and impassable rapids or falls. This fact will likely mean that future discoveries will be coastal in nature and that further inland discoveries will be highly unlikely.

Other suggested limiting factors such as low water temperatures and the availability of suitable habitat (Gibson et al. 1984; Houston 1990) are probably not limiting to Banded Killifish in Newfoundland. Shallow regions in all population locales surveyed reached upper temperature limits of at least 23°C in July and August meaning that spawning should have been easily accomplished in these areas. However, in areas where Banded Killifish were restricted in distribution to one or two lakes, abundant suitable habitat in other lakes linked by easily passable brooks and streams showed no evidence of Banded Killifish presence. This trend is evident in several of the watersheds where populations occur and indicates a more detailed study of potential habitat parameters is required.