Fishes and other consumers excrete metabolic waste products, including dissolved nutrients rich in nitrogen, which is an essential nutrient for primary production. Relatively little is known about the magnitude and variability of nutrients excreted by fishes in kelp forest ecosystems and whether consumer-derived nutrients are important for supporting kelp productivity. In this study, the supply of ammonium (NH₄⁺) excreted by the dominant fishes (30 species representing ∼85% of total fish biomass) was investigated on nearshore rocky reefs in California. Using rapid field incubations, the amount of excreted dissolved ammonium was measured as a function of body size (n = 460 individuals) and predictive models were developed relating mass to excretion rates at the family-level. Mass-specific excretion rates ranged from 0.08 to 3.45 μmol·g⁻¹·hr⁻¹, and per capita ammonium excretion rates ranged from 5.9 to 2765 μmol·individual·hr⁻¹. Ammonium excretion scaled with fish body mass to the ¾ power, as predicted by the metabolic theory of ecology; mass-specific excretion rates were higher in smaller fishes, but larger fishes contributed more ammonium per individual. When controlling for body size, ammonium excretion rates were greatest among surfperch (Embiotocidae), damselfish (Pomacentridae), and wrasses (Labridae), and the general trophic groups of planktivores and micro-carnivores. When body size differences were considered, the greatest mean excretion rates per individual were observed in larger-bodied species, such as California Sheephead (Semicossyphus pulcher) and Lingcod (Ophiodon elongatus). Empirical estimates of nutrient excretion by fishes, among the first measured in temperate kelp forests, were consistent with those in other aquatic systems. Ultimately, empirically derived excretion rates are the first step to quantifying the relative importance of consumers to nutrient cycling in kelp forest ecosystems.

鱼类和其他消费者排出代谢废物，包括富含氮的溶解营养物质，氮是初级生产的必需营养物质。关于海带森林生态系统中鱼类排出的营养物质的数量和变异性，以及消费者来源的营养物质对于支持海带生产力是否重要，人们知之甚少。在这项研究中，对加利福尼亚州近岸岩礁的主要鱼类（30 种，占鱼类总生物量的 85%）排泄的铵 (NH ₄ ⁺ )供应进行了调查。使用快速现场孵化，测量了溶解铵的排泄量作为体型的函数（n  = 460 个体），并开发了将体重与家庭水平排泄率相关的预测模型。质量比排泄率范围为0.08至3.45 μmol·g ^-1 ·hr ^-1，人均铵排泄率范围为5.9至2765 μmol·个·hr ^-1。正如生态学代谢理论所预测的那样，铵的排泄量与鱼体重的 3/4 次方成正比；较小的鱼的特定质量排泄率较高，但较大的鱼每条贡献更多的铵。在控制体型大小时，鲈鱼（Embiotocidae）、雀鲷（Pomacentridae）和濑鱼（Labridae）以及浮游动物和微型食肉动物的一般营养类群的铵排泄率最高。当考虑到体型差异时，在体型较大的物种中观察到个体平均排泄率最高，例如加州羊头羊 ( Semicossyphus pulcher ) 和灵科羊 ( Ophiodon elongatus )。对鱼类养分排泄的经验估计（在温带海藻森林中首次测量）与其他水生系统中的结果一致。最终，根据经验得出的排泄率是量化消费者对海带森林生态系统养分循环相对重要性的第一步。