Wednesday, July 15, 2009

Trout in the St. Joseph River Valley of Michigan: Relative Importance

In previous posts, I examined (a) 20th century distribution of trout and (b) species diversity and annual variation in streams within the Michigan portion of the St. Joseph River. Here, I continue my assessment of trout populations by looking at species diversity and annual variation. The information presented here is derived from the creel-census data provided by Wesley and Duffy (1999).

Throughout the entire Michigan portion of the St. Joseph River system, trout accounted for about one-quarter of the fish caught during the period 1928-1965. They were most abundant in the Lower and Mouth segments of the system, where they accounted for 94.9 and 88.6 percent of the catch, respectively. Details follow:

Trout As a Percentage of Total Catch (All Streams):
  • Headwaters: Mean = 4.8 (11 of 229 fish in 2 streams). Median = 2.8 (range 0.0 – 5.5)
  • Upper: Mean = 0.7 (20 of 2,953 fish in 7 streams). Median = 4.9 (range 0.0 – 9.8)
  • Middle: Mean = 8.9 (1,118 of 12,515 fish in 14 streams). Median = 96.5 (range 0.0 – 100.0)
  • Lower: Mean = 94.9 (3,047 of 3,210 fish in 16 streams). Median = 100.0 (range 3.6 – 100.0)
  • Mouth: Mean = 88.6 (1,176 of 1,328 fish in 15 streams). Median = 100.0 (range 0.0 – 100.0)
  • TOTAL: Mean = 26.5 (5,372 of 20,235 fish in 54 streams). Median = 100.0 (range 0.0 – 100.0)
  • Trout represented a somewhat lower percentage of the total catch in McCoy Creek (90.9 percent) than in the remaining 15 streams in the Lower valley segment (95.1 percent).

    In the 41 trout streams (i.e., streams or stream segments where trout were available and caught as a result of intentional or unintentional stocking), trout usually accounted for a majority of the fish caught. For example, trout represented more than 50 percent of the reported catch in 36 streams (88 percent), more than 90 percent of the catch in 34 streams (83 percent), and 100 percent of the catch in 28 streams (68 percent).

    Except for the poorly-sampled Headwaters and Upper valley segments, trout of one or more of the three species were predominant in the overall catch in trout streams throughout the system, accounting for 86 to 95 percent of the reported catch. Details follow:

    Trout as Percentage of Total Catch in Trout Streams:
  • Headwaters: Mean = 5.5 (11 of 201 fish in 1 stream)
  • Upper: Mean = 9.8 (20 of 204 fish in 1 stream)
  • Middle: Mean = 86.1 (1,118 of 1,299 fish in 9 streams). Median = 100.0 (range 44.2 – 100.0)
  • Lower: Mean = 94.9 (3,047 of 3,210 fish in 16 streams). Median = 100.0 (range 3.7 – 100.0)
  • Mouth: Mean = 91.5 (1,176 of 1,285 fish in 14 streams). Median = 100.0 (range 26.5 – 100.0)
  • TOTAL: Mean = 86.7 (5,372 of 6,199 fish in 41 streams). Median = 100.0 (range 3.7 – 100.0)
  • Among the eight high-diversity trout streams (i.e., streams with all three species represented in the catch) in the Lower valley segment, trout represented a slightly smaller percentage of the total catch in McCoy Creek (90.9 percent) than in the remaining seven streams (97.5 percent).

    Reference:

    Wesley, J. K., and Joan E. Duffy. 1999b. St. Joseph River assessment. Appendix 2 (.pdf). Miscellaneous historical creel data. Michigan Department of Natural Resources Fisheries Division Fisheries Report 24: 117-227. URL: http://www.michigandnr.com/PUBLICATIONS/PDFS/ifr/ifrlibra/special/reports/sr24/sr24App2.pdf

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