|In the spring of 2009, the Pennsylvania Fish and Boat Commission initiated a study to determine the contribution of hatchery fingerling trout stocking to angler catch in Sections 06 (Francis E Walter outflow to confluence Sandy Run) and 07 (confluence Sandy Run to relic dam above Palmerton) of the Lehigh River. The PFBC has been stocking fingerling trout in Sections 06 and 07 of the Lehigh River since 1982 and 2005, respectively.
A total of 18,000 fingerling brown trout marked with a pelvic clip were equally distributed in two pools (FEW Gage and Black Creek) in Section 06, and 50,000 fingerling trout (30,000 brown trout and 20,000 rainbow trout marked by an adipose clip) were equally distributed within four pools: Glen Onoko, Jim Thorpe, Bowmanstown, and East Penn Township.
PFBC Area 5 personnel with assistance from Areas 3 and 4 surveyed the Lehigh River to determine the occurrence of fin clipped fingerling trout in mid-summer, 2009. Sampling was conducted in proximity to the pools where the fingerling trout were stocked and in a few tributaries that discharged directly into the stocked pools. None of the pelvic clipped fingerling brown trout stocked in Section 06 were recaptured. A total of 16 of the adipose clipped brown trout stocked in Section 07 were recaptured (10 in the mainstem reaches and 6 from tributaries) and no adipose clipped fingerling rainbow trout (Section 07) were recaptured (Table 1).
A number (n = 54) of unclipped fingerling trout were captured (Table 1). These were principally captured from the tributary streams (70%; 38 of 54 fingerlings). Captured fingerlings in the tributaries most likely represent trout that were spawned in those waters, particularly, since these streams are known to support natural reproduction (e.g., Black Creek).
A total of 48 trout were identified as hatchery origin but 44 sub-legal and 18 legal trout were of indeterminate origin, meaning that these trout did not illustrate conclusive characteristics typical of hatchery trout. The lack of identifiable hatchery characteristics does not necessarily imply a wild spawned trout, particularly given the substantial hatchery trout (fingerling and adult) stockings into mainstem and tributary reaches of the Lehigh River. Hatchery trout characteristics typically diminish overtime, thus, making a determination of origin beyond a year impractical. However, the sub-legal trout captured in Black Creek and Glen Onoko Falls Creek most likely were spawned in those waters, since Black Creek is designated as a Class “A” brown trout water.
Table 1. Summertime recaptures of trout in Sections 06 and 07 of the Lehigh River
During October 7th and 8th, 2009, three pools including Glen Onoko, Bowmanstown and East Penn Township were night boat electrofished. A total of five adipose clipped rainbow trout ranging from 9.3 to 10.1 inches were recaptured. Pictured in Figure 1 is one of the recaptured adipose clipped rainbow trout. No fin clipped (adipose or pelvic) brown trout were recaptured. Seven legal brown trout of indeterminate origin and 10 hatchery brown trout were also caught.
Several conclusions may be drawn pertaining to the recaptured fin clipped fingerling trout. Survivorship was evident in some pools, but remains unknown in other pools, due to the lack of catch. Clipped brown trout appear to be distributing away from stocking locations. The recaptured clipped brown trout fingerlings during the summer sampling ranged from 3.7 – 5.8 inches in length at the time of recapture suggestive of some growth from their size at the time of stocking (range of 1.9 to 2.9 inches). The growth rate for the fingerling rainbow trout stocked in May (mean: 2.9 inches; range: 1.9 – 5.9 inches) was very good as compared to their size at the time of recapture in October. The fast growth rate experienced in 2009 may be reflective of the unusually cool summer season and the lack of typical prolonged summer thermal stresses that are normally experienced in this reach of the Lehigh River.
Figure 1. Adipose clipped rainbow trout stocked in the Lehigh River by the PFBC. Note the clipped lower portion of the caudal fin; this was done by the PFBC for identification purposes in case this fish was recaptured again during our October electrofishing survey.
Any determination of the success of the hatchery stocked fingerling trout program for the Lehigh River is premature at this time and ultimately relies on their contribution to angler catch. Judgment will need to be reserved for at least two to three years too allow adequate opportunity for anglers to catch clipped trout as they grow into adult size fish. The presence of marked rainbow trout in our October sampling, and their size at capture suggests that at least some of these fish survived to legal size. Hopefully these fish will hold over through the winter season and contribute to angler catch in the 2010 season and beyond. An angler has already reported catching adipose clipped rainbow trout, also in the 9-10 inch range. Therefore, we urge anglers to be aware of the potential for catching pelvic and/or adipose clipped trout for the fall of 2009 and subsequent seasons (e.g., 2010); and to please report fishing effort and total catch to us. Pertinent information is illustrated in the example below. The reporting of catch can be accomplished through PFBC web site comment page, calling PFBC biologist Daryl Pierce at 570-588-6388, e-mail email@example.com, or submitting a Lehigh River Angler Logbook (http://www.fishandboat.com/images/fisheries/afm/2007/5_lehigh_logbook.pdf).
The PFBC strongly encourages angers to refrain from fin clipping trout in the Lehigh River in an effort to preserve a clipped adipose or pelvic fin as an identifying mark for evaluating the survival of hatchery stocked fingerling trout.
Example report form: (note, data should only be entered for one angler on any one line; and start a new line for each new trip e.g., move to a different section in the same day or fished on different days, reporting of unclipped trout catch is also important).
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