The ecology of forage fish species and interactions with marine predators

我的研究计划的长期目标是调查饲用鱼类的基本生态，以及这如何影响加拿大北部海洋生态系统中捕食者的生物学。海豚是一种类似小鲤鱼的小鱼，是捕食许多无脊椎动物的重点饲料鱼物种，而大多数大型捕食者，包括西北大西洋的鳕鱼、鲸鱼和海鸟，都会捕食海豚。Capelin为营养水平之间的能量转移提供了必要的联系，因此，通常被认为是调节生态系统水平的变化。在之前NSERC资助的研究中，我发现海豚在纽芬兰沿海的深水(海底)栖息地产卵，这种物种主要在那里的海滩上产卵。我还提供了第一个直接证据，证明海豚根据栖息地特定的温度在温暖的海滩和凉爽的海底生境之间进行选择，这表明随着气候变暖，海豚对海底生境的占有率更高。虽然卵发育正常，幼虫从海底栖息地出来，但这种栖息地不被认为对产卵群体有贡献。我的第一个短期目标是阐明海底和海滩生境对招募的相对贡献，使用尖端技术来量化耳石微量化学(即激光消融电感耦合等离子体质谱)作为出生来源的自然标签。这需要通过将温度、盐度和水化学的长期测量与每个栖息地内饲养的幼虫在实验室受控的温盐和化学条件下的耳石化学结合起来，量化核心区特定生境的耳石化学特征(例如，锶、钡)，代表孵化前和孵化后的时期。这也将提供对连通性和集合种群动态的洞察，这对于有效管理和养护高度流动的海洋鱼类至关重要。在纽芬兰，由于大多数脊椎动物捕食者依赖海豚作为猎物，我的第二个目标是研究捕食者在个体水平上的可塑性，以改变海豚的密度和行为。我之前由NSERC资助的研究显示，多个海洋捕食者物种在一群每年持续的海底产卵地点附近聚集成高丰度(生物热点)，这可能是由于以最少的搜索努力增加了猎物遇到率。我将把最近小型化的动物携带的跟踪设备与基于调查的驼鹿密度和行为的变化相结合，以检查捕食者个体水平的觅食行为。还将对调查数据进行调查，以确定捕食者对不同Capelin聚集类型的偏好，以澄清捕食者和猎物之间的功能关系。由于这一多物种热点具有很高的保护价值，我的第三个目标是调查纽芬兰其他地方是否存在与海豚底层产卵地点相关的类似热点，最终目标是确定需要保护的重要区域。几个长期数据集将与短期假设驱动的研究相结合，形成许多相互关联的、基于领域的学生论文的基础。总体而言，这将提高Capelin年级强度模型的准确性，并允许为该物种和其他饲料鱼物种制定基于生态系统的捕捞规则。这将进一步发展捕食者-猎物种群动态的科学理论，以在未来的渔业做法和气候变化下维持北部海洋生态系统的结构和功能。

The long-term goals of my research program are to investigate the basic ecology of forage fish species and how this shapes the biology of predators in marine ecosystems of northern Canada. Capelin, a small minnow-like fish, is the focal forage fish species that preys on many invertebrates and is in turn preyed on by most large predators, including cod, whales and seabirds in the Northwest Atlantic. Capelin provide essential linkages for energy transfer among trophic levels and, thus, are often thought to mediate ecosystem-level changes. In previous NSERC-funded research, I discovered capelin spawning in deep water (demersal) habitat in coastal Newfoundland, where this species is primarily thought to spawn on beaches. I also provided the first direct evidence that capelin select between warm, beach and cool, demersal habitats based on habitat-specific temperature, suggesting a higher occupation of demersal habitat with predicted climate warming. Although eggs develop normally and larvae emerge from demersal habitat, this habitat is not thought to contribute individuals to the spawning population. My first short-term objective is to elucidate the relative contribution of demersal and beach habitats to recruitment using cutting-edge techniques to quantify otolith microchemistry (i.e. laser ablation inductively coupled plasma mass spectrometry) as a natural tag of natal origin. This requires quantifying habitat-specific otolith chemical signatures (e.g., Sr, Ba) in the core region, representing the period before and immediately post-hatch, by integrating long-term measures of temperature, salinity and water chemistry along with otolith chemistry from larvae raised within each habitat and under controlled thermohaline and chemical conditions in the lab. This will also provide insight into connectivity and metapopulation dynamics, which are critical for effective management and conservation of highly mobile marine fish. As most vertebrate predators rely on capelin as prey in Newfoundland, my second objective is to study the individual-level plasticity of predator foraging strategies to changing capelin density and behaviour. My previous NSERC-funded research revealed that multiple marine predator species aggregate in high abundances (`biological hotspot') near a cluster of annually persistent demersal spawning sites, likely owing to augmented prey encounter rates with minimal search efforts. I will integrate recently miniaturized animal-borne tracking devices to examine individual-level foraging behaviour of predators with survey-based shifts in capelin density and behaviour. Survey data also will be investigated to determine predator preferences for different capelin aggregation types to clarify functional relationships between predators and prey. Owing to the high conservation value of this multispecies hotspot, my third objective is to investigate whether similar hotspots associated with capelin demersal spawning sites occur elsewhere in Newfoundland, with the ultimate goal of identifying important areas to protect. Several long-term data sets will be integrated with short-term hypothesis-driven research, forming the basis of many inter-related, field-based student theses. Overall, this will improve the accuracy of capelin year class strength models and allow the development of ecosystem-based harvest rules for this and other forage fish species. This will further develop scientific theories of predator-prey population dynamics to maintain the structure and function of northern marine ecosystems under future fisheries practices and climate change.