NYSDEC Region 9 Trout Stream Monitoring Summary for 2018
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NYSDEC Region 9 Trout Stream Monitoring Summary for 2018 Scott Cornett Fishery Biologist NYS – DEC Region 9 – Allegany November, 2018 1 Overview In June, July and August 2018, Region 9 Fisheries staff, with considerable assistance from angler volunteers, DEC Lake Erie Fisheries Unit staff and USFWS staff, conducted electrofishing surveys at 44 sites on 25 of the highest quality trout streams throughout the region (Figure 1). These were the same streams and sites that had been sampled in 2016 and 2017, with only a very few changes to sites between years. Streams sampled in Allegany County were Chenunda Creek, Dyke Creek, Ford Brook, Orebed Creek and Spring Mills Creek. In Cattaraugus County, we sampled Stoddard Creek, Beehunter Creek, Fenton Brook, Elm Creek, The Ram, Mansfield Creek, Elton Creek, Lime Lake Outlet and McKinstry Creek. Hosmer Brook, Cattaraugus Creek and Spring Brook were sampled in Erie County, while Oatka Creek, Wiscoy Creek, N. Branch Wiscoy Creek, Trout Brook, Flynn Brook, Clear Creek (Arcade) and Cattaraugus Creek were done in Wyoming County. Clear Creek (Ellington) and Cherry Creek were sampled in Chautauqua County. Figure 1. Streams surveyed to monitor trout populations in 2018. 2 To better monitor long-term and short-term trends in adult trout populations throughout the region, and to evaluate year to year reproductive success, in 2016 we began to sample most of the higher quality streams in the region on a yearly basis. Peer reviewed fisheries studies have shown reproductive success of trout is often affected by environmental factors that can be region-wide in scope and can dictate future years adult population abundance. Since we could not allot additional time to this sampling over past years, we sampled a comparable number of total sample sites to past years. However, those sites were spread over many more streams and covered much more of the region, geographically. All of the sites had been sampled at least once prior to 2016 (most sites several times). This allows us to compare changes to the trout populations at those sites over time. Of course, everything comes with trade-offs and while this sampling plan gives us much better regional coverage, we do lose some finer-scale ability to see what is happening throughout individual streams. The following is a summary of population trends for each trout species throughout the region. Adult trout populations at sites in 2018 were compared with values from previous surveys to determine long-term and short-term population trends. Young-of- year numbers captured were rated as low, moderate or high and compared with catch from past years. Following this regional summary, if you desire more detailed discussion for each stream, including population graphs, they can be found in Appendix I (separate electronic file). Adult Brown Trout In 2018, 34 sites were sampled where we could assess trends in adult (yearling and older) wild brown trout population abundance. Twelve of the sites showed a long- term (>1990 through 2018) increasing population trend, fourteen sites showed a long- term decreasing trend and eight sites did not show a discernable long-term trend (Figure 3). At the three sites in southeastern Allegany County, a long-term increasing trend was seen at two sites, with one showing a decrease (Figure 3). However, all these sites had a low number of years sampled. Four of the sites in far western Cattaraugus County and eastern Chautauqua County showed long-term increasing trends in adult brown trout abundance (Figure 3), with the other two showing no discernable trend. This indicates that habitat and climate conditions may have been more conducive for brown trout reproduction and survival than we are seeing in some other parts of the region. Streams in the Cattaraugus Creek watershed show a mixed bag of trends for adult wild brown trout abundance, with four sites showing long-term increases, five showing long-term decreases and six sites showing no discernable trend (Figure 3). The other area of discernable long-term population trend for adult brown trout is in the Wiscoy Creek watershed where all eight of the sites show a long-term decrease in abundance (Figure 3). 3 Figure 3. Long-term (>1990 through 2018 surveys) trends in adult wild brown trout population abundance for sites sampled in 2018. Green dots indicate an increasing long- term trend, yellow dots indicate no discernable trend and red dots indicate a decreasing long-term trend. Note that sites had widely varying numbers of sampling years. When looking at shorter-term trends in adult wild brown trout populations, it should be noted that at seven of the eight sites in the Wiscoy Creek watershed, even though the overall trend in long-term population showed a decline, the population estimate in 2018 showed no significant difference from what we found in 2016 and 2017 (Figure 4). This may indicate that populations at those sites have stabilized. Looking region-wide it is apparent that in 2018, at most sites, for adult brown trout, population abundance was substantially lower than we found in 2016-2017, with only two sites showing increases in 2018 (Figure 4). This likely indicates there was poor reproduction in recent years (which we did see) and/or lower survival of adults than in past years. At 31 of our sampling sites where quality habitat would make us expect to find large brown trout, 19 of the sites produced at least one wild brown trout greater than 16 4 inches, eight of the sites produced at least one wild brown trout greater than 18 inches and one site produced a fish greater than 20 inches. Overall at the 31 sites, we captured 32 wild brown trout over 16 inches, nine over 18 inches and one over 20 inches. This was an increase over 2017 catches for fish >16 inches and >18 inches. One other interesting aspect of this year’s sampling was that we captured four individual wild brown trout, from three streams, which were the same fish (identified by unique spotting patterns) that had been captured, from the same pools in 2016 and 2017 (see photo examples in Appendix I, page 13). Not only had these large trout (18-20 inches long) shown high fidelity to their home pools, they also had grown very little from the previous year and were likely old fish (8-12 years). Figure 4. Adult wild brown trout population abundance in 2018 compared with abundances in 2016 and 2017 surveys. Green dots indicate higher abundance in 2018, yellow dots indicate no significant difference from 2016, 2017 and 2018 surveys and red dots indicate lower abundance in 2018 than in 2016 and 2017 surveys. 5 Adult Rainbow Trout In 2018, we sampled at 15 sites where we encountered adult wild rainbow trout. These streams are all found in the Cattaraugus Creek watershed with all but two being tributaries upstream of Springville Dam. When looking at long-term trends in adult rainbow trout abundance, we saw five sites showing long-term increases in abundance, four showing long-term decreases and six sites showing no long-term discernable trends (Figure 5). Conversely, when we compare 2018 adult rainbow trout abundances with what we found in 2016 and 2017 surveys, we found only one site to have an increased abundance. Five sites showed lower abundance in 2018 and eight sites did not show significant differences with 2016 and 2017 values (Figure 6). Figure 5. Long-term (>1990 through 2018 surveys) trends in adult wild rainbow trout population abundance for sites sampled in 2018. Green dots indicate an increasing long- term trend, yellow dots indicate no discernable trend and red dots indicate a decreasing long-term trend. Note that sites had widely varying numbers of sampling years. 6 Figure 6. Adult wild rainbow trout population abundance in 2018 compared with abundances in 2016 and 2017 surveys. Green dots indicate higher abundance in 2018, yellow dots indicate no significant difference from 2016, 2017 and 2018 surveys and red dots indicate lower abundance in 2018 than in 2016 and 2017 surveys. Adult Brook Trout While not part of this sampling program, 48 wild brook trout streams in the region were electrofished in 2015 and 2016 to obtain fin clips for genetic analysis, giving us an opportunity to assess relative abundance region-wide in those years. In most streams, the abundance of adult brook trout appeared to be high in both years (based on the length of stream we needed to electrofish to collect the clips from 50 adult fish). Particularly in 2015, but also in 2016 most streams appeared to have very high numbers of young-of- year brook trout. Yearling sized fish were very abundant in 2016, as we would expect with such good reproduction in 2015. In 2018 we sampled twelve sites where we encountered measurable wild brook trout populations. Most of these sites did not have extensive years of sampling data prior 7 to 2017, thus trend information is more limited than we have for brown and rainbow trout. Keeping in mind this limitation, we observed long-term increasing trends in abundance for adult wild brook trout at two sites, long-term decreasing trends at two sites and no discernable trends at eight sites (Figure 7). When comparing observed adult brook trout abundance between 2018 values and 2016 and 2017 values (note, some sites were not sampled in 2016), we saw five sites with lower abundance values in 2018, one site with an increased value and six sites with no difference in values between years (Figure 8). Adult wild brook trout populations typically show substantial year to year variation based on weather-influenced (winter/spring flooding) variation in the success of previous year’s reproduction.