Catchable-sized hatchery trout (hereafter, catchables) have become a staple component of many fisheries management programs throughout North America. Due to their size, catchables create immediate fisheries once they are stocked, and fisheries managers have gradually shifted towards stocking fewer, larger trout. However, the cost of growing larger fish may reduce the efficiencies of catchable stocking programs overall. We grew catchable-sized Rainbow Trout Oncorhynchus mykiss to two target average sizes (254 and 305 mm total length) at a production scale, while tracking feed expenditures to examine the costs and benefits associated with increased size-at-stocking. Although larger catchables cost 31% more in feed expenditures than those reared to a smaller average size, catch (by anglers) of larger fish increased by 100% relative to smaller fish. Consequently, if target stocking size was changed from 254 to 305 mm and feed costs were held constant by reducing the total number of fish stocked, anglers would benefit by catching larger and more fish, despite the reduction in number of fish stocked. In lentic systems, larger catchables were reported by anglers more quickly than smaller fish, so managers must consider interactions between stocking size and residence time for lentic systems supported by catchables. In lotic systems, overall catch by anglers was much lower than catch at lentic waterbodies, and all catchables were either reported by anglers quickly or failed to be reported at all regardless of size-at-stocking. Producing larger catchables for hatchery-supported fisheries serves to benefit angling and would likely increase angler satisfaction while improving efficiencies associated with hatchery catchable stocking programs.

中文翻译：

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孵化场可捕获虹鳟鱼生长至两种目标尺寸的相对成本和发布后性能

可捕获大小的孵化鳟鱼（以下简称可捕获鱼）已成为整个北美许多渔业管理计划的主要组成部分。由于它们的大小，可捕获的鱼一旦被放养就会立即产生渔业，渔业管理人员逐渐转向放养更少、更大的鳟鱼。然而，养殖较大鱼的成本可能会降低可捕获放养计划的整体效率。我们养殖了可捕获大小的虹鳟鱼Oncorhynchus mykiss到生产规模的两个目标平均尺寸（254 和 305 毫米总长度），同时跟踪饲料支出以检查与增加放养尺寸相关的成本和收益。尽管较大的可捕获物的饲料支出比饲养到较小平均尺寸的鱼多 31%，但（垂钓者）较大鱼的捕获量相对于较小的鱼增加了 100%。因此，如果目标放养尺寸从 254 毫米更改为 305 毫米，并且通过减少放养鱼的总数来保持饲料成本不变，尽管放养鱼的数量减少了，但垂钓者将通过捕获更大和更多的鱼而受益。在 lentic 系统中，垂钓者报告较大的可捕获物比较小的鱼更快，因此管理人员必须考虑由可捕获物支持的 lentic 系统的放养大小和停留时间之间的相互作用。在捕捞系统中，垂钓者的总捕捞量远低于稳定水体的捕捞量，并且垂钓者要么很快报告了所有可捕捞量，要么根本没有报告，无论放养时的大小如何。为孵化场支持的渔业生产更大的可捕捞量有助于垂钓，并可能提高垂钓者的满意度，同时提高与孵化场可捕捞放养计划相关的效率。