In the early 1990s, the Atlantic cod (Gadusmorhua) population on the Newfoundland and Labrador shelf declined dramatically, leading to a fishing moratorium in 1992. The Northern cod population has not fully recovered, possibly due to the simultaneous population collapse of an important prey type, capelin (Mallotus villosus), which migrates from the continental shelf into coastal Newfoundland to spawn every summer. Our objective was to test whether capelin availability influenced short-term dietary shifts of cod while inshore on the northeast Newfoundland coast. We quantify the dietary composition and relative abundance and biomass of prey types in cod stomachs sampled weekly or bi-weekly throughout July-August 2017 and 2018. Survey-based acoustic estimates of capelin biomass and the timing of spawning in the study area revealed that peak capelin biomass was five times higher (0.239 g/m2) and two weeks earlier (July 28) during 2018 relative to 2017 (0.048 g/m2, August 9). Cod stomachs were ~ 10 times more likely to contain capelin during 2018 relative to 2017. As capelin availability increased throughout each summer, cod shifted from a high diversity diet of lower-quality invertebrate prey (e.g., shrimp, crab) to a low diversity, capelin-dominated diet, whereby capelin presence, abundance and biomass increased. These findings indicate that capelin remains a primary prey type of cod in inshore waters during their summer growing season, but dietary proportions of capelin vary with their availability. As low dietary proportions of capelin are associated with reduced body condition and reproductive potential in cod, findings support the need for an integrated capelin-cod management approach.

中文翻译：

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毛鳞鱼（Mallotus villosus）的可用性影响纽芬兰沿海大西洋鳕鱼（Gadus morhua）的近海夏季饮食

1990 年代初期，纽芬兰和拉布拉多大陆架上的大西洋鳕鱼 (Gadusmorhua) 种群急剧下降，导致 1992 年暂停捕捞。 北方鳕鱼种群尚未完全恢复，可能是由于一种重要猎物类型的种群同时崩溃, 毛鳞鱼 (Mallotus villosus)，每年夏天从大陆架迁徙到纽芬兰沿海产卵。我们的目标是测试毛鳞鱼的可用性是否会影响纽芬兰东北海岸近海鳕鱼的短期饮食变化。我们量化了 2017 年 7 月至 8 月和 2018 年期间每周或每两周采样的鳕鱼胃中猎物类型的饮食成分、相对丰度和生物量。基于调查的毛鳞鱼生物量和研究区域产卵时间的声学估计表明，与 2017 年相比，2018 年毛鳞鱼生物量峰值（0.239 g/m2）和两周前（7 月 28 日）高出五倍（0.048 g/m2） ，8 月 9 日）。与 2017 年相比，2018 年鳕鱼胃中含有毛鳞鱼的可能性是 2017 年的 10 倍。随着每年夏季毛鳞鱼供应量的增加，鳕鱼从低质量无脊椎动物猎物（例如虾、蟹）的高多样性饮食转变为低多样性饮食，毛鳞鱼占主导地位的饮食，毛鳞鱼的存在、丰度和生物量增加。这些发现表明，在夏季生长季节，毛鳞鱼仍然是近海水域鳕鱼的主要猎物类型，但毛鳞鱼的饮食比例随其可用性而变化。