PDF(Pubmed)
Abstract：
This study investigates effects of subtle methodological choices on the estimation and biological interpretation of age, growth and reproductive parameters for harbour porpoises. The core analyses are based on a focal Norwegian data set built on samples from 134 harbour porpoises caught incidentally in gillnet fisheries along the Norwegian coast during autumn 2016 and spring 2017. Two contrasting practices for interpretation of seasonal and ontogenetic characteristics of tooth growth layer formation resulted in significant age differences among spring samples of young porpoises and for older animals across seasons. In turn, these differences affected estimates of age at maturity and asymptotic lengths, respectively. We also found significant differences in male age at maturity between two well-documented maturity criteria and between mathematical estimators of age at maturity for both sexes. Two different criteria for corpus albicans classification furthermore resulted in different patterns of ovarian corpora accumulation, which may affect some estimates of fecundity rates and contaminant loads. Both corpora accumulation patterns were also found in reanalysed data from German and Greenlandic porpoises. Based on tabulated overviews of methodological choices made in previous harbour porpoise studies, we argue that several of the issues mentioned above have wider relevance and may affect the validity of meta-analyses as a tool for estimating harbour porpoise sensitivity to extrinsic pressures. Differences in cause of death (COD) composition between data sets can have a similar effect. We demonstrate this in a meta-analysis of published harbour porpoise pregnancy rates, showing significantly higher values for trauma-killed samples compared to samples comprising mixed COD categories. COD also affected the estimated impacts of three previously analysed extrinsic predictors as well as an added predictor for vessel noise levels. We discuss the potential contributions of methodological, biological and anthropogenic factors in shaping observed regional differences in estimates of harbour porpoise life history parameters.
摘要：
这项研究调查了微妙的方法选择对年龄的估计和生物学解释的影响，港口海豚的生长和繁殖参数。核心分析基于挪威重点数据集，该数据集基于2016年秋季和2017年春季在挪威沿海刺网渔业中偶然捕获的134只港海豚的样本。解释牙齿生长层形成的季节性和个体发育特征的两种截然不同的做法导致幼年海豚的春季样本和跨季节的老年动物之间存在显着年龄差异。反过来,这些差异影响了对成熟年龄和渐近长度的估计，分别。我们还发现，在两个有据可查的成熟标准之间以及男女成熟年龄的数学估计之间，男性成熟年龄存在显着差异。此外，两种不同的白色语料库分类标准导致了不同的卵巢语料库堆积模式，这可能会影响对繁殖率和污染物负荷的一些估计。在德国和格陵兰海豚的重新分析数据中也发现了两种语料库积累模式。根据先前港口海豚研究中对方法选择的列表概述，我们认为，上述几个问题具有更广泛的相关性，可能会影响荟萃分析作为评估港口海豚对外部压力敏感性的工具的有效性。数据集之间的死因（COD）组成差异可能具有类似的影响。我们在对已发表的海豚怀孕率的荟萃分析中证明了这一点，与包含混合COD类别的样品相比，创伤致死样品的值明显更高。COD还影响了三个先前分析的外部预测因子以及容器噪声水平的附加预测因子的估计影响。我们讨论了方法论的潜在贡献，生物和人为因素形成观察到的港口海豚生活史参数估计的区域差异。
