Assessment of Fin Erosion by Comparison of Relative Fin Length in Hatchery and Wild Trout in Utah

Abstract

We measured all fins of 600 hatchery trout sampled from all 10 state fish hatcheries in Utah, and of wild fish sampled as controls comprising 58 rainbow trout (Oncorhynchus mykiss), 33 cutthroat trout (O. clarki), and 54 brown trout (Salmo trutta). A strong linear correlation was found between fin length and total body length (100–300 mm) for all fins of wild rainbow trout. "Relative fin length" (fin length/total body length × 100) proved to be a useful comparative measure, as this statistic was not biased by fish length in the wild fish sampled (all slopes <0.01%). Interspecific comparison of wild rainbow, cutthroat, and brown trout showed slight but statistically significant differences in some fin lengths. In intraspecific comparisons, hatchery fish had significantly shorter (10–50%) rayed fins than wild fish. The dorsal fin was most severely eroded in rainbow and brown trout, followed by the pectoral, anal, ventral, and caudal fins, in cutthroat trout the pattern was the same except that pectoral fins had more extensive erosion than dorsal fins. No species was clearly more susceptible to fin erosion in hatcheries, but the Fish Lake – DeSmet strain of rainbow trout had significantly shorter fins than other rainbow trout strains.

Fin condition of fish kept in aquacultural systems

“…There are probably no fi n damages in natural conditions (Turnbull et al, 1996;Hoyle et al, 2007;Stejskal et al, 2011). Fin erosion occurs only in the intensively reared fi sh (Bosakowski and Wagner, 1994;Ellis et al, 2008). Worsened fi n condition infl uences swimming abilities and surviving of reared fi sh in natural conditions (Bosakowski and Wagner, 1995).…”

“…Process of fi n damaging proceeds from margins till fi n base (Person-Le Ruyet et al, 2007). Mostly damaged fi ns are dorsal and pectoral in salmonids (Turnbull et al, 1998;Rasmussen et al, 2007), subsequently anal, caudal and abdominal (Bosakowski and Wagner, 1994). With European perch (Perca fl uviatilis) there were paired fi ns -pectoral and abdominal in rearing facility mostly aff ected.…”

Fin development in stream- and hatchery-reared Atlantic salmon

“…Relative fin index (fin length/total length; see Kindschi, 1987) is a method of quantifying fin development that has been used in numerous studies to date (Bosakowski and Wagner, 1994;Barnes et al, 1996;Winfree et al, 1998). The use of fin indices, however, relies on the linear increase of fin length as a function of total length, which may not be the case depending on the species, developmental stage, fin and size range of fish sampled.…”

“…Body weight (nearest 0.1 g), fork length, and total length were recorded for each fish. Fins were measured as outlined in Bosakowski and Wagner (1994). All fins, excluding the adipose, were measured for the longest distance parallel to the fin rays.…”

“…The problem of fin erosion is so extensive that it is often used as an identifier of recently stocked fish, and as an indicator of overall fish health. The dorsal and pectoral fins are most susceptible to degeneration within the hatchery environment due to interactions with abrasive surfaces and through aggressive contact with other fish (Abbott and Dill, 1985;Bosakowski and Wagner, 1994). Many other factors have been implicated in causing fin erosion including overcrowding, water quality, temperature, feed type, malnutrition, bacterial infection, handling, and exposure to excessive sunlight and environmental contaminants.…”