The present study analyses the coverage of epibiont Distaplia cf. stylifera (Ascidiacea: Holozoidae) and five environmental variables (Sal, SST, DO, sea surface Chl-a concentration and pH) as potential factors to explain a mass mortality event in a restored population of the pen shell Atrina maura (Bivalvia: Pinnidae) in a subtropical bay of the Gulf of California, Mexico. Annual autumn surveys in 2015, 2016 and 2017 (Nov–Dec) and an additional summer survey in 2016 (Jun) showed that the tunicate was first observed at low densities in a few sampling sites during 2015 and rapidly expanded along the pen shell banks in 2016. Tunicate manual removal was carried out in two small areas during Sep-Nov 2016 and Jan–Mar 2017. The mass mortalities of A. maura detected in 2016 and 2017 resulted in a high economic loss for regional fishers. A Generalised additive model (GAM) indicated that the substrate provided by A. maura was the only significant factor associated to the rapid expansion (measured as the proportion of coverage) of D. cf. stylifera. Paradoxically, the recovery success in the A. maura population increased substrate availability for the tunicate epibiont, facilitating an abrupt and fast colonisation process on the pen shell banks, resulting in A. maura mass mortality events in 2016 and 2017. Our model predicts that D. cf. stylifera coverage effects begin to occur when the density of A. maura is > 47 inds./250 m². A second GAM demonstrated that the main driver of A. maura mortality was ascidian coverage, and salinity, SST and DO were secondary driver factors. We concluded that the density of dead A. maura increases when the coverage of D. cf. stylifera is >8%, salinity >37.3 PSU, SST <26.9 °C and DO > 5.06 mg O₂/L. Early harvesting of A. maura to decrease substrate availability at the first signs of D. cf. stylifera population growth can avoid significant economic losses in the future.

本研究分析了表皮生物 Distaplia的覆盖范围，参见。stylifera（Ascidiacea：Holozoidae）和五个环境变量（Sal、SST、DO、海面 Chl- a浓度和 pH 值）作为解释恢复的笔壳Atrina maura种群中大规模死亡事件的潜在因素（双壳类动物：Pinnidae）在墨西哥加利福尼亚湾的一个亚热带海湾。2015 年、2016 年和 2017 年（11 月至 12 月）的年度秋季调查以及 2016 年（6 月）的额外夏季调查表明，2015 年期间在几个采样点首次以低密度观察到被囊类动物，并在2016. 2016 年 9 月至 11 月和 2017 年 1 月至 3 月期间在两个小区域进行了人工去除被囊类动物。 2016 年和 2017 年发现的A. maura大量死亡给区域渔民带来了巨大的经济损失。广义加性模型（GAM）表示，由设置在基板A.莫拉是相关联的快速膨胀（如覆盖的比例测得）的唯一显著因子D. CF 。花柱. 矛盾的是，A. maura种群的恢复成功增加了被囊类外生物的底物可用性，促进了笔壳库上突然和快速的定植过程，导致2016 年和 2017年A. maura大规模死亡事件。我们的模型预测D . 参见 当A. maura的密度> 47 inds./250 m ²时，stylifera覆盖效应开始出现。第二个 GAM 表明A. maura死亡率的主要驱动因素是海鞘覆盖率，而盐度、SST 和 DO 是次要驱动因素。我们得出结论，当D. maura的覆盖率增加时，死A. maura的密度会增加。参见 stylifera >8%，盐度 >37.3 PSU，SST <26.9 °C 和 DO > 5.06 mg O ₂ /L。早期收获A.莫拉以的最初迹象减少底物可用性D. CF 。stylifera人口增长可以避免未来的重大经济损失。