Summary Juvenile fish are important prey for marine birds and mammals. The objective of this study is to characterize the juvenile fish near the Isles of Shoals. Neuston nets and beach seines were deployed from 2021-2025. The neuston net was deployed 118 times and the beach seine was deployed 7 times. Neuston net fish catches were ichthyoplankton ranging from about 5-35 mm total length (TL) and beach seine fish catches were juvenile fish ranging from about 15-210 mm TL. Neuston net catches were high in 2022 (up to about 20 ichthyoplankton per deployment) and low thereafter (typically 0-2 per deployment). Beach seine catches typically were a few hundred fish and were more consistent from year to year. In the neuston net catch, common fish species were red hake (Urophycis chuss), white hake (Urophycis tenuis) and fourbeard rockling (Enchelyopus cimbrius). In the beach seine catch, common fish species were American sand lance (Ammodytes americanus), Atlantic herring (Clupea harengus) and Atlantic tomcod (Microgadus tomcod). The largest beach seine catch of herring was in 2025 (159).

Juvenile fish are important prey for marine birds and mammals. During June 2021, three juvenile fish were caught during surface water sampling near the Isles of Shoals and were identified as red hake (Urophycis chuss), white hake (Urophycis tenuis) or fourbeard rockling (Enchelyopus cimbrius), which are morphologically similar species (Marancik et al. 2020). These three species are prey of the terns (Gemma Clucas, Elizabeth Craig, pers. comm.) and red and white hake are prey of the seals (Veo et al., 2021) found at the Isles of Shoals. Juvenile red and white hake spend their first months drifting at or near surface water, sometimes under floating eelgrass or rockweed, reaching ~10 cm by fall (Steiner et al., 1982). Juvenile fourbeard rockling also spend their first months at or near surface water (Bigelow and Schroeder, 1953). Red and white hake may be less nutritious than other seal and tern prey such as Atlantic herring (Clupea harengus) and American sand lance (Ammodytes americanus), yet if they are common at the water surface, may make an important contribution to these predators’ diets, similar to prey patterns for Steller sea lions in southeast Alaska (Sigler et al., 2009). During the 2021 sampling, eight neuston net tows were completed during surface water sampling. The intent of this project is to continue this sampling and to characterize the juvenile fish near the Isles of Shoals.