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

Population Sizes and Trends

Population estimates have not been attempted with this species previous to the current research (Houston 1990). Schnabel mark-recapture estimates were performed in the Indian Bay watershed in July and August of 1999. Water temperatures were lower in July and likely contributed to an estimate of 1209 individuals (95% confidence limits 619-3 423) whereas the August estimate was for 20 569 individuals (95% confidence limits 12 529-40 201). The relationship between temperature and killifish abundance in fyke net catches in three study sites between 1999-2001 was significant when the data are log transformed with a p-value of 0.000 (Figure 4) ( R-sq=0.190, F‑ratio=11.776, ss=45). Any future investigation of population size would best be performed in late July and through August when water temperatures are higher and killifish abundance and activity are at their highest levels (Chippett In prep.). Figure 4 indicates the relationship between water temperature and catch per unit effort of Banded Killifish in three Newfoundland lakes. In the absence of additional estimates, these data do not provide suitable information on population trends, but merely describe the condition of the Indian Bay population in 1999.


Figure 4: Relationship Between Banded Killifish Catch Per Unit Effort and Water Temperature in Three Newfoundland Lakes

Figure 4: Relationship between Banded Killifish catch per unit effort and water temperature in three Newfoundland lakes.

Loch Leven, Third Pond (Indian Bay Watershed), and Freshwater Pond (Chippett In prep.).

The catch per unit effort (CPUE) values presented in Table 1 are much higher for the Indian Bay watershed than for the Loch Leven and Freshwater Pond populations. The species is so restricted in distribution in the Indian Bay watershed that nets were always placed in areas where Banded Killifish were known to occur based on prior experience. As a result, the Indian Bay sampling may have targeted areas with greater numbers of Banded Killifish in the area. However, in the other populations, particularly Freshwater Pond, the range of the species is larger and individual fish would be found throughout a larger area making sampling site selection a factor. The large CPUE’s and the maximum numbers of killifish caught in fyke nets in July and August indicate that this species is locally abundant at Loch Leven, Freshwater Pond and Indian Bay, which is in agreement with Houston (1990). In Third Pond, in the Indian Bay watershed, Banded Killifish numbers reached maximums of nearly 200 killifish per net in late July and early August (Figure 4). At Loch Leven, large schools of Banded Killifish of approximately 25-40 individuals are easily observed in the sandy shallows, particularly on warm sunny days (personal observations). The size and movements of these schools in the shallows create the illusion of “bubbling” or “boiling” water as described by Gilhen (1974).

 

Table 1: Mean Catch Per Unit Effort (CPUE – Individuals/set) Values for Three Representative Newfoundland Banded Killifish Populations (Chippett In prep.)
Population# of net setsx CPUE
(Catch per Unit Effort)
Indian Bay2442
Loch Leven1029
Freshwater Pond1023