Whaling, one of the most extensive and prolonged global commercial hunting operations, pushed many large whales to the brink of extinction. To understand how evolutionary processes may be directly impacted by the consequences of exploitation, we assessed age-dependent population dynamics, reproductive tactics, and reproductive success of 485 male humpback whales (Megaptera novaeangliae) from a recovering breeding ground in New Caledonia. Over 19 years (2000-2018), the population age structure switched from a left-skewed, rapidly increasing low-density population toward a more evenly distributed age structure when abundance was higher in later years. Concurrent with the change in population age structure across time, there was a shift in age-related male mating tactics. Most strikingly, during years of higher abundance, the key reproductive tactics of singing and escorting were over-represented by older age categories when compared with the underlying age structure, suggesting age- and/or density-related tactic choice in males. This behavioral shift corresponded with an increase in the relative reproductive success of the oldest males during periods of higher abundance compared with lower abundance. Overall, our work suggests that at lower population densities, young males were less constrained by age-related restrictions on reproductive success. A reduction of age-related sexual selection could have acted to buffer genetic diversity loss during a time of lower abundance, when this was most critical. Integrating these changes in the pattern of sexual selection with population dynamics provides critical insights into the evolutionary consequences of exploitation and recovery in long-lived species.
Bycatch of marine mammals in fisheries is a critical conservation issue worldwide, and Chile is no exception. Pinnipeds such as the South American sea lion (Otaria byronia, SASL) frequently encounter fishing gear along the Chilean coast. Despite widespread evidence of these interactions, few studies have spatially assessed SASL bycatch risk across multiple fisheries for this species. This study applies the Bycatch Risk Assessment (ByRA) toolbox, a GIS-based model, to evaluate and compare the risk of SASL bycatch across nine Chilean purse-seine and trawl gear fisheries based on data from on-board scientific observer logs from 2015 to 2019. Our findings identify trawl fisheries, particularly those targeting southern hake (Merluccius australis), as posing the highest bycatch risk, especially during the non- reproductive season when SASL exhibit broader spatial distribution. Purse-seine fisheries presented lower risk overall, with the industrial northern fleet showing the highest relative risk. Spatial patterns revealed that risk is concentrated in nearshore areas, where the overlap between the distribution of SASL and fishing activity is the greatest. These results provide a robust, spatially explicit foundation for prioritizing mitigation measures, including the mandatory use of exclusion devices and seasonal restrictions. Our approach underscores the potential mitigation provided by evidence-based management of marine mammal bycatch in Chile and contributes information toward the assessment of compliance with domestic and international regulations.
Coastal phytoplankton blooms are important drivers of regional and global marine primary production. Recently documented increases in coastal phytoplankton blooms in the first quarter of the 21st century may be a consequence in part of changing environmental conditions and have important ecological implications. Here, we explore coastal phytoplankton dynamics in Cape Cod Bay, MA, USA. We use a 20-year phytoplankton ecology dataset to identify potential drivers of the increasing prevalence of two regionally-rare phytoplankton taxa: a coccolithophore thought to thrive in the global open ocean, and a dinoflagellate genus with potentially toxic members. Using metatranscriptomics, we show that these minor phytoplankton taxa leverage unique strategies to gain a competitive advantage under nutrient limitation compared to traditionally dominant taxa and compared to a diatom taxon that became modestly more abundant over the study period. Our results highlight the ecological dynamics arising from long-term shifts in temperature and nutrient status in coastal ecosystems. ### Competing Interest Statement The authors have declared no competing interest. Simons Foundation, 874439, 931886, 549931 National Science Foundation, 2019589 Department of Energy, DE-SC0020347 Woods Hole Oceanographic Institution
Ocean color remote sensing has primarily been used to monitor surface phytoplankton distributions, but recent developments have extended its application to detecting higher trophic-level organisms. The copepod Calanus finmarchicus contains the carotenoid pigment astaxanthin, which has specific optical signals that can be detected by satellite sensors. In the Gulf of Maine (GoM), C. finmarchicus plays a critical ecological role as the dominant copepod species and a key prey item for the endangered North Atlantic right whale (Eubalaena glacialis). This study, focusing on the GoM, evaluates a satellite-derived Astaxanthin Equivalent Index (AEI), as a proxy for surface abundance of astaxanthin-rich zooplankton. MODIS-Aqua satellite AEI estimates from 2003 to 2022 were compared with stage- and species-resolved in situ zooplankton data from Continuous Plankton Recorder near-surface transects, as well as with depth-stratified net tows and conical-net surface and oblique tows from other programs. In situ abundance values were converted into AEI units (mu g/m3) using stage- and species-specific pigment scaling. While the AEI was calibrated for C. finmarchicus, comparisons indicated that the satellite signal also included contributions from other astaxanthin-containing taxa, particularly Centropages typicus. Stronger correspondence was observed when astaxanthin content from both C. finmarchicus and C. typicus was considered, but the degree of correlation varied across datasets. This variability likely reflects satellite overestimation due to other astaxanthin-rich signals and may also be influenced by differences in in situ sampling methods. High satellite AEI values co-occurred with behavioral observations of right whale surface skim-feeding in Cape Cod Bay, indicating that AEI products may help characterize potential feeding habitats for the species. These comparisons highlight the potential of astaxanthin-based satellite indices to complement field observations in zooplankton monitoring and right whale habitat assessment.
The Manila clam, Ruditapes philippinarum, is one of the world’s most widely introduced marine bivalves, but its establishment has not yet been documented in the Northwest Atlantic Ocean. Here we report the first records of reproducing populations of R. philippinarum from Massachusetts, U.S.A. Observations were collected through opportunistic field surveys, community science platforms (i.e., iNaturalist), and correspondence and discussions with commercial and recreational shellfish harvesters. These observations revealed the presence of R. philippinarum at multiple locations in Cape Cod and Boston Harbor between 2023 and 2025, with northernmost occurrences now reaching Salem Sound, north of Boston. Live individuals from Cape Cod ranged from 31 to 71 mm in shell length (SL). Similar size ranges were documented in Boston Harbor, with additional targeted sediment sampling documenting early settlers (500 µm SL) and young juveniles (1–7 mm SL), confirming this species to be established and reproducing. Community science contributions and engagement with shellfishers expanded the known distribution of R. philippinarum and prompted additional search efforts in 2025, highlighting the importance of broad community engagement in early detection. Further work is needed to determine the potential source population, understand the species’ role in Northwest Atlantic ecosystems, and track its potential spread.
