Returning to the original post and taking Maurice's theme into account: You'll recall that the sampling location on this stream was always the same, although the distance electrofished varied. The longest electrofishing run in 1978 produced the least trout...a single, most likely stocked fish. This despite the stocking of 700 trout through the spring. Water temp by June 28,1978 in mid-afternoon was already 25 C, or about 75-76 F....not good for maintaining a trout population through the summer. Air temp was 29 C....hot. Additionally, the fish community was indicative of annual warm summer water temps. It included warm water species such as common shiners, bluntnose minnows, and warm to moderate transitional margined madtoms, some smallmouth bass , but lacked rosyside dace, a standard York Co moderate to cool transitional species. The same stocking rate continued through 2001, but the next electrofishing sampling occurred 7/23/96. Water temp in mid-afternoon was 16 C, Air 23 C. One stocked RT was captured along with 16 wild BT, including fingerlings, and two stocked BT. The fish community was changing....the warm water common shiner and bluntnose minnow were gone. The transitional madtom remained. Rosyside dace , which had not been present before were now abundant. A few (3) small SMB were still present, but the fish community indicated that long term temps were cooling down. Remember, the wild trout appeared despite the same numbers of trout being stocked by the PFBC. It was not until 2002 that the stocking number dropped from 700 to 300, but the wild trout population was already present and growing in 1996. As an aside, given exponential population growth, it could have conceivably been a Class A equivalent by 2002. In Dec, 2013, we find a Class A equivalent population of wild BT and one stocked RT. The first electrofishing run produced 99 wild BT, with 50 more total caught in the following two electrofishing runs on the same day on the same site (a depletion population estimate was being conducted). Common shiners and bluntnose minnows were still gone and margined madtoms were also gone. Rosyside dace remained. I attribute the population change of trout and other indicator species to cooling water temps over the years associated with gradually maturing vegetation, not necessarily land use changes, upstream from the woodland where the samples were taken. I'm talking riparian vegetation here. The brown trout population and species that would have been affected primarily by temperatures responded (to cooling water temps in summers) before stocking rates changed. Similarly, Conowingo Creek went from no wild trout to Class A in about 10 years when riparian vegetation was allowed to grow. This should suggest something to folks interested in habitat projects. You may not need to even get into the water to have a very positive response in a trout population.
