McCasker Nicole, Humphries Paul, Meredith Shaun, Klomp Nicholas
School of Environmental Sciences, Charles Sturt University, Albury, New South Wales, Australia; Institute of Land, Water and Society, Charles Sturt University, Albury, New South Wales, Australia.
Aquatic Environment Branch, Department of Fisheries, Cloisters Square, Western Australia, Australia.
PLoS One. 2014 Oct 9;9(10):e109317. doi: 10.1371/journal.pone.0109317. eCollection 2014.
Understanding the causal mechanisms that determine recruitment success is critical to the effective conservation of wild fish populations. Although recruitment strength is likely determined during early life when mortality is greatest, few studies have documented age-specific mortality rates for fish during this period. We investigated age-specific mortality of individual cohorts of two species of riverine fish from yolksac larvae to juveniles, assaying for the presence of a "critical period": A time when mortality is unusually high. Early life stages of carp gudgeons (Hypseleotris spp.) and unspecked hardyhead (Craterocephalus stercusmuscarum fulvus)-two fishes that differ in fecundity, egg size and overlap between endogenous and exogenous feeding-were collected every second day for four months. We fitted survivorship curves to 22 carp gudgeon and 15 unspecked hardyhead four-day cohorts and tested several mortality functions. Mortality rates declined with age for carp gudgeon, with mean instantaneous mortality rates (-Z) ranging from 1.40-0.03. In contrast, mortality rates for unspecked hardyhead were constant across the larval period, with a mean -Z of 0.15. There was strong evidence of a critical period for carp gudgeon larvae from hatch until 6 days old, and no evidence of a critical period for unspecked hardyhead. Total larval mortality for carp gudgeon and unspecked hardyhead up to 24 days of age was estimated to be 97.8 and 94.3%, respectively. We hypothesise that life history strategy may play an important role in shaping overall mortality and the pattern of mortality during early life in these two fishes.
了解决定补充成功率的因果机制对于有效保护野生鱼类种群至关重要。尽管补充强度可能在死亡率最高的早期生活阶段就已确定，但很少有研究记录鱼类在此期间特定年龄的死亡率。我们调查了两种河鱼从卵黄囊幼虫到幼鱼阶段各个队列的特定年龄死亡率，以确定是否存在“关键期”：即死亡率异常高的时期。每隔一天收集鲤鱼 gudgeon（Hypseleotris spp.）和无斑强壮头鱼（Craterocephalus stercusmuscarum fulvus）这两种在繁殖力、卵大小以及内源性和外源性摄食重叠方面存在差异的鱼类的早期生命阶段样本，持续四个月。我们对22个鲤鱼gudgeon和15个无斑强壮头鱼的四天队列拟合了生存曲线，并测试了几种死亡率函数。鲤鱼gudgeon的死亡率随年龄下降，平均瞬时死亡率（-Z）范围为1.40 - 0.03。相比之下，无斑强壮头鱼在幼体阶段的死亡率保持恒定，平均-Z为0.15。有强有力的证据表明鲤鱼gudgeon幼虫从孵化到6日龄存在关键期，而无斑强壮头鱼没有关键期证据。估计鲤鱼gudgeon和无斑强壮头鱼在24日龄前的幼体总死亡率分别为97.8%和94.3%。我们假设生活史策略可能在塑造这两种鱼类早期生命阶段的总体死亡率和死亡模式中发挥重要作用。
