Point Blue Conservation Science, Petaluma, California, 94954, USA.
H. T. Harvey and Associates Ecological Consultants, Los Gatos, California, 95032, USA.
Ecol Appl. 2017 Jan;27(1):10-25. doi: 10.1002/eap.1435.
Extraction of Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea began in 1997, following a management plan that targets the largest fish with a goal of reducing the spawning biomass by 50% over 35 yr. We investigate the potential long-term consequences of the reduced availability of this prey for Weddell seals (Leptonychotes weddellii). Energy demands in seals are acute, especially immediately following lactation, when females must recover substantial mass and cope with molting costs. We tested the hypothesis that toothfish are critically important for adult female seals during this period. Toothfish body mass is three orders of magnitude greater, and its energy density nearly double that of the most common seal prey, Antarctic silverfish (Pleuragramma antarcticum). Reduction or elimination of toothfish consumption could impair a female's ability to sufficiently recover and successfully produce a pup in the following pupping season. Our goals are to (1) illustrate mechanisms and conditions whereby toothfish depletion might plausibly affect seal population trends; (2) identify measurable parameters of the seals' ecology that may help better understand the potential negative impact of toothfish depletion on seal populations; and (3) promote a precautionary management approach for the fishery that includes monitoring of seal populations We constructed a set of inter-linked models of seal diving behavior, physiological condition, and demography based on existing information. We evaluate the effect of the following factors on seal mass recovery and intrinsic population growth rates: fishery depletion rate, daily diving limits, probability of a successful dive, and body mass recovery target. We show that loss of toothfish has the greatest potential impact on seal populations' growth rate. Under some scenarios, populations may decrease at >10% per year. Critical parameters to better understand fishery impacts include prevalence and size of toothfish in the seals' diet; the relationship between diet and the rate of mass recovery; and female breeding propensity in relation to body condition at the end of the molting period. Our results lend support to concerns about the potential negative impact of toothfish extraction in the Ross Sea; and to advocate for a precautionary management approach by the fishery.
南极犬牙鱼（Dissostichus mawsoni）于 1997 年在罗斯海开始捕捞，当时制定了一项管理计划，旨在捕捞最大的鱼，目标是在 35 年内将产卵生物量减少 50%。我们调查了这种猎物减少对威德尔海豹（Leptonychotes weddellii）的潜在长期影响。海豹的能量需求非常迫切，尤其是在哺乳期后，此时雌性海豹必须恢复大量体重并应对换羽成本。我们测试了这样一个假设，即犬牙鱼在这段时间对成年雌性海豹至关重要。犬牙鱼的体重是海豹最常见猎物南极银鱼（Pleuragramma antarcticum）的三个数量级，能量密度几乎是南极银鱼的两倍。如果减少或消除犬牙鱼的消耗，可能会损害雌性海豹在下一个繁殖季节充分恢复和成功繁殖幼崽的能力。我们的目标是：（1）说明机制和条件，说明犬牙鱼的枯竭如何可能影响海豹种群趋势；（2）确定海豹生态学的可测量参数，这些参数可能有助于更好地理解犬牙鱼枯竭对海豹种群的潜在负面影响；（3）促进对渔业的谨慎管理方法，包括监测海豹种群。我们根据现有信息构建了一组相互关联的海豹潜水行为、生理状况和种群动态模型。我们评估了以下因素对海豹体重恢复和内在种群增长率的影响：渔业枯竭率、每日潜水限制、成功潜水的概率和体重恢复目标。我们表明，犬牙鱼的丧失对海豹种群增长率的潜在影响最大。在某些情况下，种群数量可能会以每年超过 10%的速度减少。更好地理解渔业影响的关键参数包括海豹饮食中犬牙鱼的流行率和大小；饮食与体重恢复速度的关系；以及雌性在换羽期结束时的繁殖倾向与身体状况的关系。我们的研究结果支持了对罗斯海犬牙鱼捕捞可能产生负面影响的担忧，并主张渔业采取谨慎的管理方法。
