Investigation of Techniques for Differentiating Stocked Hatchery Reared and Native Fingerling Striped Bass
Project number: AFS-9
Final Report Date: 1975
Period Covered: July 1, 1970 June 30, 1974
Authors: Carl Hall and Daniel Holder
To determine a distinguishing characteristic and/or suitable tagging or marking technique for differentiating stocked hatchery reared striped bass fingerlings from native river populations of striped bass fingerlings.
Fish culture techniques were developed at Richmond Hill Fish Hatchery for rearing fingerling striped bass, Morone saxatilis (Walbaum), from small size (1.5 to 2 inches) to advanced size (4 to 6 inches). Average survival of 121,585 small fingerlings reared to advanced size was 54.0 percent during the study period. Survival was highest (73%) during the fourth year as rearing techniques improved.
Use of scale growth increment and length frequency comparisons between hatchery reared and native striped bass were unsuccessful for identifying hatchery fish reared under controlled growth conditions. Difficulty in scale interpretation and variation in scale growth increment and size distribution between both groups of fish were the primary reasons for this.
Of the various external tags or marks compared relative to their suitability for identifying large numbers of stocked hatchery reared fingerlings, the modified Floy anchor tag gave best results; however, tag loss did occur. The standard FD-68 Floy was the next best tag. The Carlin tag was determined to be unsuitable because of difficulty of application and higher mortality from bacterial infections after tagging. The fin-clip as a mark was unsuccessful due to fin regeneration.
Preliminary work using a micro-magnetic tag (1 mm color-coded wire filament) gave promising results. Indications are that this tag will be useful for tagging large numbers of striped bass fingerlings.
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