We address the problem of optimal size‐selective exploitation in an age‐structured fish population model by systematically examining how density and size dependency in growth, mortality and fecundity affect optimal harvesting patterns when judged against a set of fisheries objectives. The study offers five key insights. First, while minimum‐length limits often maximize the biomass yield, exploitation using harvest slots (i.e. regulations that protect both immature and very large individuals) can generate within 95% of maximum yield; harvest slots also generally maximize the number of fish that are harvested. Second, density dependence in growth and size‐dependent mortality predict more liberal optimal size limits than those derived under assumptions of no density and size dependence. Third, strong density dependence in growth maximizes the catch of trophy fish only when modest harvest is introduced; the same holds for numbers harvested, when the stock–recruitment function follows the Ricker type. Fourth, the inclusion of size‐dependent maternal effects on fecundity or egg viability has only limited effects on optimal size limits, unless the increase in fecundity with mass (“hyperallometry”) is very large. However, large hyperallometry in fecundity shifts the optimal size limit for biomass yield from the traditional minimum‐length limit to a harvest slot. Fifth, harvest slots generally provide the best compromises among multiple objectives. We conclude that harvest slots, or more generally dome‐shaped selectivity to harvest, can outperform the standard minimum‐length selectivity. The exact configuration of optimal size limits crucially depends on objectives, local fishing pressure, the stock–recruitment function, and the density and size dependency of growth, mortality and fecundity.

中文翻译：

---

当目标是实现多个与捕捞和捕捞有关的渔业目标时，通过收获槽保存大鱼的性能优于经典的最小长度限制

通过系统地检查在根据一组渔业目标进行判断时生长，死亡率和繁殖力的密度和大小依赖性如何影响最佳捕捞方式，我们解决了年龄结构化鱼类种群模型中的最佳规模选择开采问题。该研究提供了五个关键见解。首先，虽然最小长度限制通常使生物量产量最大化，但利用收获时段（即保护未成年和非常大的个体的法规）进行开采可以产生最大产量的95％之内；收获槽通常还使收获的鱼类数量最大化。其次，与没有密度和尺寸依赖性的假设所得出的最佳尺寸限制相比，增长中的密度依赖性和尺寸依赖性的死亡率预测了更为自由的最佳尺寸限制。第三，仅在进行适度收获的情况下，生长中对密度的强烈依赖性才能最大限度地提高奖杯鱼的捕获量；当库存补充功能遵循Ricker类型时，收获的数量也是如此。第四，除非产卵量随质量增加（“超量度法”）很大，否则将产卵量对产卵率或卵生存力的影响包括在内对最佳产蛋量的影响有限。但是，繁殖力大的超异位测定法将生物量产量的最佳大小限制从传统的最小长度限制转移到了收获时段。第五，收获时段通常在多个目标之间提供最佳折衷。我们得出的结论是，收获槽，或更普遍地说是圆顶形的收获，可以胜过标准的最小长度选择性。