Ischua Creek (2008)
Fisheries Survey Summary
In conjunction with a season-long angler survey, the DEC Fisheries Unit, along with angler volunteers, sampled trout populations in the catch and release section of Ischua Creek during August, 2008. The 2.2 mile section of stream is characterized by good adult trout habitat with abundant, deep pools, log jams and some old cribbing structures. Summer water temperatures are ideal for wild brown trout, never exceeding 70 degrees. This section is stocked with yearling brown trout in three increments and two-year-old brown trout in two increments. This year the section also got a stocking of surplus yearling brook trout in June. The catch and release regulation went into effect on October 1, 2004 and this year's sampling was designed to duplicate a survey done in 2004, prior to the special regulation.
In this year's sampling, we captured 47 adult wild brown trout, 26 hatchery brown trout and 20 hatchery brook trout. Sampling sites were 630, 800 and 960 feet in length. At the three sites, we found much lower numbers of adult wild brown trout than in the 2004 survey. For all the sites combined in 2008, we found an estimated 104 wild, adult brown trout per mile, compared with 424/mile in 2004. The estimated biomass of wild brown trout this year was 17 lbs/acre compared with 27 lbs/acre in 2004. Breaking the catch down by age classes, showed that in 2004, 91% of the catch was made up of one year olds and two year olds, while in 2008, only 64% were one or two year olds. In 2004, 9% of the catch was age three and older fish while this year 36% of the catch was made up of these older fish, three of which measured 19, 21.5 and 23.5 inches. In 2004, of the 192 wild brown trout captured, five fish were >16 inches (3%), while this year seven of the 47 fish captured were >16 inches (15%). This year's skewed ratio of older to younger fish accounts for the large drop in numbers of fish per mile from 2004 and the smaller decrease in the biomass, with so much of the catch this year made up of large individuals and few yearlings caught. There is little natural reproduction of trout in the main stream. Most of it is believed to occur in two small tributaries, one of which is sometimes inaccessible to spawning fish due to beaver dams on the tributary. It is likely that the small numbers of yearling and two year old wild brown trout this year is due to poor spawning and/or rearing conditions in the tributaries in 2005, 2006 and 2007.
Low numbers of hatchery brown trout were captured in this year's survey, with the estimated number being only 57/mile. They are stocked at the rate of 650/mile (yearlings and two-year-olds combined). In a catch and release section, this appears to be very low survival. An angler survey conducted during 2008 on the stream found very low catch rates for trout prior to the second increment stocking, and it is likely that the first increment of brown trout (stocked March 17th) suffered very high non-angler mortality. In 2004, prior to the catch and release regulation, there were an estimated 115 hatchery brown trout per mile remaining at the time of the survey. We did encounter a number of the surplus yearling brook trout that were stocked in June. Most were at one site only a few hundred feet above a stocking point.
It appears that Ischua Creek's wild and stocked trout populations have not been positively influenced by the catch and release regulation as was hoped when it was implemented. However, the lower numbers of wild brown trout are likely due to environmental factors affecting reproduction and rearing and the low numbers of stocked trout may be due to poor natural survival after stocking. Data from this survey combined with the angler survey will be used in the future to determine whether to keep this regulation in effect.