Patrick Gellings and Emily Hastings (2013 Interns) Kris Wright (Faculty Advisor) Biology Department University of Wisconsin-Platteville

Transcription

1 1 SAIF (A) Final Project Report ( ) Examining Stream Restoration in Southwest Wisconsin: Assessment of the Trout Diets in Southwest Wisconsin Steams Patrick Gellings and Emily Hastings (2013 Interns) Kris Wright (Faculty Advisor) Biology Department University of Wisconsin-Platteville

2 2 Introduction: The quality and quantity of prey items available to brown trout (Salmo trutta) can be important in the maintenance of their populations (Chapman 1966). Quantity and quality may be affected by allochthonous input and substrate size, which in turn may affect brown trout life history (Young 1980, Bilby & Bisson 1992). Juvenile brown trout tend to show a preference toward particular macroinvertebrate taxa, which differs from adult brown trout (Brynildson et al. 1973, Glova & Sagar 1991). Angling, anthropogenic, and environmental pressures also have the potential to drastically affect trout populations and their prey (Marschall & Crowder 1996). Therefore understanding what food items are available and consumed by trout may provide insight into how different populations deal with these pressures (Brafia et al. 1992, Marschall & Crowder 1996, Hari et al. 2005, Alexander & Hansen 2011). In Southwest Wisconsin many trout streams are located in or near agricultural settings, which can affect prey abundance and, as a result, trout populations. These changes may be brought about by excessive stream erosion from various cattle crossings and the lack of vegetation in the riparian zones. Increased erosion can lead to increased fine sediment load, which can affect the type and number of macroinvertebrates present as a food source for trout populations. The primary objectives of this study were to examine the potential food sources and diurnal diets of brown trout in Southwest Wisconsin. The primary hypothesis was that brown trout will prefer macroinvertebrates from the drift/surface area, which is congruent with other studies (Ringler 1979, Cada et al. 1987). The secondary hypothesis was that there will be shift in diet as adult brown trout become larger. Materials and Methods: In the summer of 2013, sampling was conducted primarily on the upper Blue River in southwest Wisconsin. There were a total of ten sites sampled on the Blue

3 3 River (north of Montfort, WI) including Carpenter, Zoha, Sime, Wolenec, Addison, Carpenter, Adametz, Simplot, Winker, and Kite along with one site on the McPherson Branch (west of Ellenboro, WI) (Figure 1). Habitat, invertebrates, fish populations and trout diets were sampled at each site. Sampling occurred in early June through late July, with the Carpenter site being sampled both in the early and late parts of the summer. Additionally, a timed sample at the Wolenec site was done where diet samples were taken at 6am, noon, and 6pm. Habitat sampling used Wisconsin DNR standards. Habitat samples were collected at each of the twelve transects along the site at four equally spaced points across each transect. Data collected consisted of river depth, embeddedness, width, substrate type present, overhead coverage, and macrophyte coverage. Substrate type was visually estimated as a percentage at each of the four points along a transect, and macrophyte and overhead cover were estimated as percentages along the entire transect. Invertebrate sampling occurred at six random transects used during the habitat sampling. Invertebrate sampling consisted of using a m 2 Surber sampler to collect invertebrates from the streambed. Five of the six samples were sorted on-site for ten minutes in the field, while the entire sixth sample was preserved in 75% ethanol and processed in the lab within the month. Fish sampling included the use of two backpack electro fishers consisting of one single pass covering the entire 300 meter site. Processing of the fish involved measurements for body length (mm) and identification on site and then released back into the stream. Fish diet sampling was done via gastric lavage with a filter basket, a filter, and a water bottle filled with the site s water. Water squirted into the mouth/stomach to flush out the stomach contents into the filter set-up. The fish was then measured, identified, and then placed into a holding bucket for release. The stomach contents within the filter were then persevered in ethanol with an ID tag

4 4 (fish species, date, stream, site, and length) to be processed at the lab within the month collected. Approximately 21 fish were sampled at each site, but due to availability, a minimum of 15 fish was still considered representative of the site. Data analysis included an electivity index of what brown trout appeared to prefer in their diet. The index (E= (R-P)/(R+P) where E was electivity, R was the number of macroinvertebrates found in nature, and P was the number of prey items found in brown trout diets) was performed based on the macroinvertebrate samples and fish diets. The electivity index was done with the 5 most abundant macroinvertebrate taxa groups: Diptera, Ephemeroptera, Trichoptera, Mollusca, and Arthropoda. Results: Habitat There was a great deal of habitat variability among the sites. Average depth ranged from (± STD) meters at Blue River Carpenter site to (± STD) meters at Blue River Kite site, while average embeddedness ranged from (± STD) meters at Blue River Carpenter View site to (± STD) meters at Blue River Winker site (Figure 2). Average wetted channel width ranged from (± STD) meters at Blue River Carpenter site to (± STD) meters at Blue River Addison site (Figure 3). Substrate composition did not vary greatly site to site: Adametz had the least amount of fines and sand of all the sites sampled, while Kite had the largest amount of bedrock, boulder and large rock of all the sites. The rest of the sites were composed mostly of a combination of fines, sand, gravel, and cobble (Figure 4). Average percent macrophyte coverage ranged from 2.42% (±4.91 STD) at Blue River Zoha site to 25% (± STD) at Blue River Sime (Figure 5). Macroinvertebrates Macroinvertebrate totals ranged from an average of 3.33/m 2 at Addison to

5 5 118/m 2 at Simplot (Figure 6). There were five taxa that were most abundant; Diptera, Ephemeroptera, Arthropoda, Trichoptera, and Mollusca. Of the five most abundant taxa, Diptera made up the highest percent of all the macroinvertebrates found at the sites sampled on the Blue River. Fish Communities Overall 10 species of fish were found over the ten sites. Several of these species were rare at each site (although they were included in any calculations). The total number of fish ranged from 61 at Winker to 325 at Carpenter. The sites that were sampled on Blue River had high proportions of Mottled Sculpin and various trout species (Figure 7). Trout numbers including young of year trout ranged from 18 at Zoha to 200 at McPherson Branch site (Figure 8). Trout populations at all sites were dominated by brown trout, with very few rainbow trout and no brook trout being found at any site (Figure 8). The average length of brown trout ranged from (± STD) millimeters (mm) at Zoha to (± STD) mm at Kite (Figure 9). The 18 June survey of Carpenter found a total of 288 fish while the 15 July sampling yielded a total of 325 fish. The same species were present in both samples with the exception of rainbow trout being present in the late summer sample and absent in the early summer sampling. There was no noticeable shift in overall numbers of each individual species present from one sample to the next (Figure 10). Fish Diets There were five main taxa consumed by brown trout: Arthopoda with (± STD) items, Mollusca with (± STD) items, Empheroptera with (± STD) items, Trichoptera with (± STD) items, and Diptera with (± STD) items (Figure 11). Other items that were investigated included Coleoptera, Odonata, Hemiptera, Archanida, pupal forms of aquatic invertebrates, crayfish, invertebrates of terrestrial origins, and fish.

6 6 The total number of all items found in all fish diets was collected. The site with the highest number of items found in all diet samples was the McPherson site with 736 total items while the lowest number came from Blue River Sime site with just 63 total items (Figure 12). The overall average electivity for Diptera was (±0.355 STD), Ephemeroptera was (±0.593 STD), Trichoptera was (±0.753 STD), Mollusca was (±0.714 STD), and Arthropoda was (±0.382 STD) (Figure 13). There appeared to be no difference in diets between smaller brown trout ( mm) and larger ones ( mm) (Figure 14). Timed Diet Samples Of the diet items found at three different times of day at Wolenec, the five main taxa were again found, along with parts of crayfish and terrestrial invertebrates. A total of 300 items were found in samples at the 6am sample, 527 items at noon, and 103 items at the 6pm sample (Figure 15). Discussion: Brown trout predominately consumed five taxa: Ephemeroptera, Diptera, Trichoptera, Mollusca, and Arthropoda. This exception was not unexpected because excessive fines have been found to negatively impact Ephemeroptera (Broekhuizen et al. 2001). It was hypothesized that brown trout would consume more drift/surface prey items such as terrestrials caught on the surface or macroinvertebrate taxa in those locations, which was what was found by other studies (Ringler 1979, Cada et al. 1987). Instead it was found that brown trout consumed what was most available such as Arthropoda, a readily available food item in most streams studied. One study found a similar thing where brown trout ate prey relative to the number present in nature (Ball 2009). There was no shift in diets as adult brown trout became larger, which was

7 7 not what was hypothesized. It appeared that there might have been a shift in how many Mollusca were consumed, but that was due to an anomaly. Two small brown trout were found to have consumed upwards of 50 Mollusca, which skewed our data. Therefore, there was no evident verification of a shift in diets. The information provided by this study can be applied in similar locations. In agricultural settings, where streams have or have had higher sediment input, the brown trout appeared to not have their food preferences readily available, which would be surface and drift prey (Ringler 1979, Cada 1987). Instead, brown trout are resorting to items that are more available. Because of the trout population s indifference in their food, adult brown trout appear to not shift their diet preferences as they become larger. Because of this phenomena, the adult trout population that was sampled may have different characteristics than trout in other populations that have access to a preferred food source. While this study did not focus on comparing trout populations from different geographic locations, future studies should examine this cause and the effect it may have on adult trout. Overall, brown trout appeared to be indiscriminate of what they consumed due to the lack of food preferences being available. What was near the bottom of the food chain appeared to affect these brown trout populations differently than in non-agricultural locations. Further investigation into brown trout diets and what is available to consume will be needed because there may be a link to the health of a stream if brown trout were becoming indiscriminate consumers.

8 8 Literature Cited Alexander, G.R. and Hansen E.A Sand sediment in a Michigan trout stream, part II. Effects of reducing sand, bedload on a trout population. North American Journal of Fisheries Management 3: Wisconsin River Ball, J.N On the food of the brown trout of llyn tegid. Journal of Zoology 137: Bilby, R. E. and Bisson, P. A. 1992: Allochthonous versus autochthonous organic matter contributions to the trophic support of fish populations in clearcut and oldgrowth forested streams. Canadian Journal of Fisheries and Aquatic Sciences 49: Brafia, F., Nicieza, A.G., Toledo, M.M Effects of angling on population structure of brown trout, Salmo trutta L., in mountain streams of Northern Spain. Hydrobiologia 237: Broekhuizen, N., Parkyn, S., Miller, D. 2001: Fine sediment effects on feeding and growth in the invertebrate grazers Potamopyrgus antipodarum (Gastropoda, Hydrobiidae) and Deleatidium sp. (Ephemeroptera, Leptophlebiidae). Hydrobiologia 457: 1-3. Brynildson, O.M., V.A. Hacker, and T.A. Klick Brown Trout: Life History, Ecology, and Management. Wisconsin Department of Natural Resources, Publication 234. Cada, G.F., Loar J.M., Cox, D.K Food and feeding preferences of rainbow trout and brown trout in southern Appalachian streams. American Midland Naturalist 117: Chapman, D. W Food and space as regulators of salmonid populations in streams. American Naturalist, 100:

9 9 Glova, G. J., and Sagar, P. M. 1991: Dietary and spatial overlap between stream populations of anative and two introduced fish species in New Zealand. Australian Journal of Marine and Freshwater Research 42: Hari, R.E., Livingstone, D.M., Siber, R., Burkhardt-Holm, P., Guttinger, H Consequences of climatic change for water temperatures and brown trout populations in Apline rivers and streams. Global Change Biology 12: Marschall, E.A. and Crowder, L.B. 1996: Assessing population responses to multiple anthropogenic effects: a case study with brook trout. Ecological Applications 6: Ringler, N.H Selective predation by drift-feeding brown trout (Salmo trutta). Jour. of the Fisheries Research Board of Canada 36: Young, K. 1980: Soil conservation protects the trout. Soil and Water June: 7-8.

10 10 Winker Kite Simplot Adametz Carpenter Sime Addison Wolenec Zoha Figure 1: Study area on the Blue River within Southwest Wisconsin showing each of the nine sites that were sampled.

11 Figure 2. Average depth (m) and embeddedness (m) (± 1 STD) at each site sampled in the Blue River and McPherson in SW Wisconsin during summer

12 Figure 3: River width (m) (±1 STD) at each site sampled in the Blue River and McPherson in SW Wisconsin during the summer of

13 Figure 4: Average substrate composition (%) at each site sampled from the Blue River and McPherson in SW Wisconsin during the summer of

14 Figure 5: Average percent macrophyte coverage (± 1 STD) at each site sampled on the Blue River and McPherson in SW Wisconsin during the summer of

15 Figure 6: Total number of macroinvertebrates found at each site from the Blue River during the summer of

16 Figure 7: Total numbers of fish sampled at each of the Blue River and McPherson sites in SW WI during the summer of

17 Figure 8: Total number of trout species sampled at each of the Blue River and McPherson sites in SW WI during the summer of

18 Figure 9: Average size of all brown trout species sampled from the Blue River and McPherson sites in SW WI during the summer of 2013at each site. 18

19 /18/2013 7/15/2013 Young of Year Brook Stickleback Mottled Sculpin Longnose Dace Fantail Darter Common Shiner White Sucker Creek Chub Rainbow Trout Brown Trout Figure 10: Composition of fish populations at Carpenter site of the Blue River from both 6/18/13 and 7/15/13.

20 Figure 11: Average number of each prey item found per brown trout taken from species sampled from the Blue River and McPherson during the summer of

21 Figure 12: Total number of items found in all brown trout diet samples taken from the Blue River and McPherson sites during the summer of

22 Diptera Ephemeroptera Trichoptera Mullusca Arthropoda Figure 13: Electivity index of Brown Trout showing preference in diets of species taken from the Blue River during the summer of 2013.

23 Figure 14: Average number of each prey item (± 1 STD) of brown trout according to length of each individual trout taken from the Blue River during the summer of

24 Figure 15: Total number of trout diet items at Wolenec site per timed sample taken at 6 am, noon, and 6pm on 4 August