Akkaya Bas Aylin, Christiansen Fredrik, Amaha Öztürk Ayaka, Öztürk Bayram, McIntosh Caley
Faculty of Fisheries, Istanbul University, Beyazit, Istanbul, Turkey.
Turkish Marine Research Foundation, Beykoz, Istanbul, Turkey.
PLoS One. 2017 Mar 15;12(3):e0172970. doi: 10.1371/journal.pone.0172970. eCollection 2017.
Marine traffic is threatening cetaceans on a local and global scale. The Istanbul Strait is one of the busiest waterways, with up to 2,500 vessels present daily. This is the first study to assess the magnitude of short- and long-term behavioural changes of the endangered Black Sea harbour porpoises (Phocoena phocoena relicta) in the presence of marine vessels within the Istanbul Strait. Markov chains were used to investigate the effect of vessel presence on the transition probability between behavioural states (diving, surface-feeding and travelling), and to quantify the effect on the behavioural budget and bout length (duration of time spent in a given state) of porpoises. Further, the changes on swimming directions of porpoises in relation to vessel speed and distance was investigated using generalized linear models. In vessel presence, porpoises were less likely to remain in a given behavioural state and instead more likely to switch to another state. Because of this, the bout length of all three behavioural states decreased significantly in the presence of vessels. The vessel effect was sufficiently large to alter the behavioural budget, with surface-feeding decreasing significantly in the presence of vessels. However, when taking into account the proportion of time that porpoises were exposed to vessels (i.e. 50%), the measured effect size was not large enough to significantly alter the animals' cumulative (diurnal) behavioural budget. Additionally, vessel speed and distance had a significant effect on the probability of porpoises showing a response in their swimming directions. The southern and middle sections of the Istanbul Strait, which have the heaviest marine traffic pressure, had the lowest porpoise sightings throughout the year. Conversely, northern sections that were exposed to a lesser degree of marine traffic hold the highest porpoise sightings. The effect shown in this study in combination with increasing human impacts within the northern sections should be considered carefully and species-specific conservation actions, including establishment of protected areas, should be put in place to prevent the long-term consequences of marine traffic on the Black Sea harbour porpoise population.
海上交通在地方和全球范围内都对鲸类动物构成威胁。伊斯坦布尔海峡是最繁忙的水道之一，每天有多达2500艘船只通行。这是第一项评估濒危黑海港湾鼠海豚（Phocoena phocoena relicta）在伊斯坦布尔海峡内有船只存在时短期和长期行为变化程度的研究。马尔可夫链被用于研究船只存在对行为状态（潜水、水面觅食和游动）之间转换概率的影响，并量化对鼠海豚行为预算和行为回合时长（在给定状态下花费的时间长度）的影响。此外，使用广义线性模型研究了鼠海豚游泳方向相对于船只速度和距离的变化。在有船只存在的情况下，鼠海豚不太可能停留在给定的行为状态，而是更有可能切换到另一种状态。因此，在有船只存在时，所有三种行为状态的回合时长都显著减少。船只的影响足够大，足以改变行为预算，在有船只存在时水面觅食显著减少。然而，考虑到鼠海豚暴露于船只的时间比例（即50%），所测量的效应大小不足以显著改变动物的累积（每日）行为预算。此外，船只速度和距离对鼠海豚在游泳方向上做出反应的概率有显著影响。伊斯坦布尔海峡海洋交通压力最大的南部和中部区域，全年的鼠海豚目击数量最少。相反，受海洋交通影响较小的北部区域，鼠海豚目击数量最多。本研究中显示的影响，再加上北部区域日益增加的人类影响，应予以仔细考虑，并且应采取包括建立保护区在内的针对特定物种的保护行动，以防止海上交通对黑海港湾鼠海豚种群产生长期影响。
