Distinguishing and Employing Two Species of Fish in Assessment of Stream Quality
Biotic indices (bioindicators) can be individual species, species groups, or communities of species used to assess habitat quality. But, to be used effectively, managers require basic information on species used as indicators, including species distribution, differentiation between similar species, and environmental conditions associated with species presence. We addressed these problems concurrently in two related species, the Mottled Sculpin (Cottus bairdii) and the Slimy Sculpin (Cottus cognatus), as habitat quality indicators in the Manistee River in Michigan, USA. We determined the abundance and distribution of these species and related their presence to concurrent in-stream measurements of temperature, dissolved oxygen, pH, conductivity, turbidity, and stream quality score based on macroinvertebrate diversity. Cladistic analyses of CO1 supported recognition of Mottled Sculpin and Slimy Sculpin as distinct species and confirmed initial field identification to species using morphological characteristics. Both species were most abundant in headwater regions, decreased downstream, and were sympatric at 5 of 12 (42%) locations. Mottled Sculpin were associated with lower conductivity, pH, and stream quality scores. Slimy Sculpin were associated with higher levels of DO and lower levels of turbidity. As a management indicator species of the US Forest Service, Mottled Sculpin alone may be ineffective as a habitat quality indicator, but concurrent use of Mottled Sculpin and Slimy Sculpin as a related-species complex might allow sufficient coverage to permit assessment of stream quality if species-specific differences in environmental tolerances are precisely determined.
Locations of 12 sampling sites on the Main Branch (MB), North Branch (NB), and tributary streams (TS) of the Manistee River examined for presence and absence of Mottled Sculpin (Cottus bairdii) and Slimy Sculpin (C. cognatus) associated with local environmental stream conditions in the upper Manistee River and its tributaries in Michigan (USA), June and July, 2015, approximately 44°29″ to 44°54″N, 84°50″ to 85°37″W. Bold black lines in the southwest portion of the figure denote the northern (horizontal) and eastern (vertical) boundaries of the Manistee Unit of the Huron-Manistee National Forests in this study area. The numerical sequence of sites is ordered to reflect descending elevation. Six associated sites (AS) on other nearby rivers (four sites) and the upper Manistee (one site) and lower Manistee River (one site) where sculpin were also collected are not shown in this figure. See Table 1.
Minimum spanning network of the 12 Cottus haplotypes from the Manistee River, Michigan (USA), June and July 2015. Each dash on the branches represents a base pair difference. Circles represent haplotypes and are labeled with the haplotype number and “MOS” for Mottled Sculpin and “SLS” for Slimy Sculpin.
(A) Maximum parsimony bootstrap consensus tree of 10,000 bootstrap replicates of the same 12 Cottus CO1 haplotypes and 4 outgroups of other fish species (Culaea inconstans, Neogobius melanostomus, Salvelinus fontinalis, and Umbra limi) computed in PAUP*. Numbers above branches represent the percentage of 10,000 replicates in which that clade was recovered. Haplotypes are labeled with the haplotype number; haplotypes 1–5 are Mottled Sculpin, and 6–12 are Slimy Sculpin. (B) Phylogram of 12 Cottus CO1 haplotypes and 4 outgroups of other fish species (Culaea inconstans, Neogobius melanostomus, Salvelinus fontinalis, and Umbra limi) computed in PAUP* with distance as the criterion from the upper Manistee River, Michigan (USA), June and July 2015. Branch lengths are proportional to the genetic distance along them. Given the number of base pairs included in the analysis, a single base pair difference is equivalent to 0.001 substitutions per site on this phylogenetic tree.
Relationship (Poisson regression) between catch per unit effort (CPUE) and elevation decline (m) from highest elevation for sites with Mottled Sculpin (Cottus bairdii) or Slimy Sculpin (C. cognatus) present in the upper Manistee River and its tributaries, Michigan (USA), June and July 2015. Dashed line indicates decline in abundance with elevation for Mottled Sculpin. Solid line indicates decline in abundance with elevation for Slimy Sculpin.
Violin plots of relationships between water quality parameters and absence or presence of Mottled Sculpin (Cottus bairdii) and Slimy Sculpin (C. cognatus) in the upper Manistee River, Michigan (USA), June and July 2015. Measurements of conductivity in ms/cm, dissolved oxygen (DO) in mg/L, pH, temperature in °C, and turbidity in nephelometric turbidity units (NTU). Stream quality scores were based on orders of macroinvertebrates discovered, with the presence of less tolerant macroinvertebrates elevating the score. >48 = Excellent, 34–48 = Good, 19–33 = Fair, <19 = Poor (Michigan Clean Water Corps, 2006). Comparisons with asterisks had significantly different distributions at P < 0.10 (*) and P < 0.05 (**).
Contributor Notes
Associate Editor: M. P. Davis.