The Effect of Raceway Grading on Return to Creel for Catchable‐Sized Hatchery Rainbow Trout

Abstract

Hatchery trout of catchable size (i.e., about 250 mm total length; hereafter termed "catchables"), which are stocked into put-and-take fisheries, are expensive to raise, so fisheries management agencies strive to modify rearing practices to maximize the proportion of stocked catchables that anglers catch. We graded fish in production-level hatchery rearing units at both fingerling and catchable size, dividing the fish into "leaders" (herein, the larger fish in a rearing unit, separated during a grading event) and "laggers" (the smaller fish). We hypothesized that (1) grading and immediate stocking of catchable leaders and short-term retention and continued feeding of catchable laggers might increase lagger growth and result in a larger average size of fish being stocked (relative to fish from ungraded raceways), potentially improving overall return to creel for the graded group and (2) grading and separation of fingerling leaders and laggers early in the rearing process may reduce competition between smaller and larger fish for the remainder of the rearing period, potentially improving overall poststocking return to creel for the entire group without the need for catchable grading at the time of stocking. We found that grading catchables just prior to stocking slightly increased the mean size at stocking (compared with ungraded control fish) for the first stocking period, which resulted in slightly higher return to creel for stocked fish. However, across the entire stocking period and with equal feed between groups, mean size at release was nearly identical between the graded and the control fish, as was return to creel by anglers. Grading fingerlings to separate leaders and laggers for the remainder of the rearing period also had no positive effect on angler catch. Our findings suggest that production-level grading is ineffective at increasing the growth of laggers, so it will not increase overall size at stocking. Consequently, improvements in angler catch are unlikely to materialize from grading hatchery trout prior to stocking them into put-and-take fisheries.Stocking catchable-sized hatchery trout (i.e., about 250 mm total length [TL]; hereafter termed "catchables") into put-and-take fisheries has long been used to create recreational fisheries in waters that cannot support wild trout or can support so few that no trout fishery would exist without the stocking program (Butler and Borgeson 1965;Johnson et al. 1995). While such fisheries are popular among anglers (Park 2007;Hunt et al. 2017), raising catchables is expensive (Johnson et al. 1995;Hunt et al. 2017;Losee and Phillips 2017). Thus, maximizing the proportion of stocked catchables that anglers catch is a common goal for fisheries management agencies that are engaged in such hatchery programs.The postrelease performance of catchable trout (in terms of angler catch) can be influenced by the conditions that they face both prior to and after stocking. Numerous studies have reported about the influence of hatchery rearing practices on the postrelease perfo...

Relative Cost and Post‐Release Performance of Hatchery Catchable Rainbow Trout Grown to Two Target Sizes

“…The need for more post-release evaluations of hatchery trout catchable stocking programs was identified over 30 years ago (Hartzler 1988), yet such evaluations remain relatively scarce. One exception to this scarcity is the growing body of literature indicating that larger catchables are more likely to be caught by an angler than smaller catchables (Mullan 1956;Yule et al 2000;Cassinelli et al 2016;Losee and Phillips 2017;Cassinelli and Meyer 2018;Meyer and Cassinelli 2020). However, all of these studies evaluated size of catchables as a secondary objective or tested size-at-release across small geographic and temporal scales.…”

“…Length data of all tagged fish were scaled to ensure model convergence. of a stocking period, and catch of size-graded fish by anglers is equivalent to that of ungraded fish (Meyer and Cassinelli 2020). Consequently, increasing the target length during production may be the most effective method of maximizing the proportion of stocked catchables that are caught by anglers.…”

Fisheries Volume 46 Number 8 August 2021

“…The need for more post-release evaluations of hatchery trout catchable stocking programs was identifi ed over 30 years ago (Hartzler 1988 ), yet such evaluations remain relatively scarce. One exception to this scarcity is the growing body of literature indicating that larger catchables are more likely to be caught by an angler than smaller catchables (Mullan 1956 ;Yule et al 2000 ;Cassinelli et al 2016 ;Losee and Phillips 2017 ;Cassinelli and Meyer 2018 ;Meyer and Cassinelli 2020 ). However, all of these studies evaluated size of catchables as a secondary objective or tested size-at-release across small geographic and temporal scales.…”

“…Length data of all tagged fi sh were scaled to ensure model convergence. of a stocking period, and catch of size-graded fi sh by anglers is equivalent to that of ungraded fi sh (Meyer and Cassinelli 2020 ). Consequently, increasing the target length during production may be the most effective method of maximizing the proportion of stocked catchables that are caught by anglers.…”

Effects of Baffles on Raceway Cleaning, Fin Erosion, In‐Hatchery Survival, and Postrelease Angler Catch of Catchable‐Sized Hatchery Rainbow Trout

“…To facilitate angler reporting of tagged fish, anchor tags were labeled with "IDFG," a tag reporting phone number, the Web site address, and a unique tag number. While it is well understood that anglers do not report every tagged fish that they catch (Pollock et al 2001;Meyer et al 2012), for this study the relative raw angler tag return rates between baffle and control groups provided a measure of postrelease performance differences (see Meyer and Cassinelli 2020;Branigan et al 2021).…”