A first assessment of the distribution and abundance of large pelagic species at Cocos Ridge seamounts (Eastern Tropical Pacific) using drifting pelagic baited remote cameras

Mapping Important Shark and Ray Areas (ISRAs) in the Central and South American Pacific: Existing knowledge and data needs

Identifying critical habitats is key to the conservation and recovery of threatened species. A third of chondrichthyans (sharks, rays, and chimaeras) are threatened with extinction but robust biological and ecological information to delineate critical habitats for many species remains limited. Here, we investigated (1) research outputs and trends across the Central and South American Pacific region to determine whether sufficient information was available to identify critical habitats; (2) whether regional Important Shark and Ray Areas (ISRAs) were spatially representative; (3) what species and which ecological traits were most commonly used in the delineation of critical habitats; and (4) discuss how ISRAs can inform research priorities and area-based management in support of chondrichthyan conservation. Sixty-five ISRAs were identified for 97 of 190 chondrichthyan species occurring in the region (51%). Across key life-history processes, reproductive areas were most identified (n = 50). Of 821 published studies (2,160 entries), 31.48% (28% entries) primarily focused on fisheries and 48.51% included enough information to inform the ISRA process. Most (58.98%) of these studies originated from Mexico (n = 342, 744 entries) and Ecuador (n = 147, 276 entries). France and Honduras had the least regional research outputs relevant to apply the ISRA Criteria. Significant ecological data gaps were identified in oceanic (including areas beyond national jurisdiction), deepwater (>200 m), and along the southern part of the region (i.e., southern Chile). Deepwater species, chimaeras, and 21% of threatened species had knowledge gaps that did not allow the identification of ISRAs. If area-based management decisions in this region were based on ISRAs, and effectively implemented and enforced, diversity hotspots and at least 97 species could receive protection, including 79% of threatened species and 54% of those considered range-restricted. Increased monitoring and research efforts, with a corresponding increase in funding to fill existing gaps is key to support the identification of important habitats across this region.

Assessing scientific knowledge on Ecuadorian bony fishes from a scientometric perspective

Bony fishes play a pivotal role in Ecuador's social, economic, and ecological aspects. However, the current state of scientific knowledge on this group remains poorly understood. This study aims to assess the scientific output related to Ecuadorian bony fishes, identifying both well-researched and understudied areas. A scientometric analysis was conducted using the Scopus database, evaluating 265 peer-reviewed publications on marine and freshwater bony fishes. The results revealed that 55.5% of studies focused on marine environments, 41.9% on freshwater ecosystems, and 2.6% on mixed environments. The earliest study was published more than 130 years ago, with a marked increase in research output since 2018. Geographic and regional disparities in research efforts were evident, with the Galapagos Islands hosting the highest number of studies at the provincial level and the coastal region leading in regional publications. Additionally, there has been a notable increase in the participation of women in research over time; however, it remains significantly below parity. English was the dominant language in these publications. On average, the delay between data collection and publication was 8.43 years, which may lead to outdated or ineffective management decisions. This underscores the importance of continually updating data to ensure the accuracy of conservation status assessments. Both marine and freshwater species that were endemic have been less studied compared to non-endemic species. Most of the studied species were categorized as "least concern," although a significant proportion of species classified as "data deficient" have started to be investigated by Ecuadorian researchers. The categories "endangered" and "near threatened" were the least studied, highlighting the urgent need for conservation initiatives targeting these vulnerable taxa. Biases in the number of studies among families, species, and geographic distribution indicate the need to expand research efforts to underrepresented taxa and regions. This analysis underscores the necessity of diversifying methodologies and broadening the research focus to more comprehensively address the challenges associated with the conservation and management of bony fishes in Ecuador.

Studying Chondrichthyans Using Baited Remote Underwater Video Systems: A Review

Cartilaginous fish face significant threats due to overfishing and slow reproductive rates, leading to rapid declines in their populations globally. Traditional capture-based surveys, while valuable for gathering ecological information, pose risks to the health and survival of these species. Baited Remote Underwater Video Systems (BRUVS) offer a non-invasive alternative, allowing for standardized surveys across various habitats with minimal disturbance to marine life. This study presents a comprehensive review of BRUVS applications in studying cartilaginous fish, examining 81 peer-reviewed papers spanning from 1990 to 2023. The analysis reveals a significant increase in BRUVS usage over the past three decades, particularly in Australia, South Africa, and Central America. The most common BRUVS configurations include benthic setups, mono-camera systems, and the use of fish from the Clupeidae and Scombridae families as bait. BRUVS have been instrumental in studying 195 chondrichthyan species, providing insights into up to thirteen different aspects of the life histories. Moreover, BRUVS facilitate the monitoring of endangered and data-deficient species, contributing crucial data for conservation efforts. Overall, this study underscores the value of BRUVS as a powerful tool for studying and conserving cartilaginous fish populations worldwide.

A decade of submersible observations revealed temporal trends in elasmobranchs in a remote island of the Eastern Tropical Pacific Ocean

No-take marine protected areas (MPAs) can mitigate the effects of overfishing, climate change and habitat degradation, which are leading causes of an unprecedented global biodiversity crisis. However, assessing the effectiveness of MPAs, especially in remote oceanic islands, can be logistically challenging and often restricted to relatively shallow and accessible environments. Here, we used a long-term dataset (2010-2019) collected by the DeepSee submersible of the Undersea Hunter Group that operates in Isla del Coco National Park, Costa Rica, to (1) determine the frequency of occurrence of elasmobranch species at two depth intervals (50-100 m; 300-400 m), and (2) investigate temporal trends in the occurrence of common elasmobranch species between 2010 and 2019, as well as potential drivers of the observed changes. Overall, we observed 17 elasmobranch species, 15 of which were recorded on shallow dives (50-100 m) and 11 on deep dives (300-400 m). We found a decreasing trend in the probability of occurrence of Carcharhinus falciformis over time (2010-2019), while other species (e.g. Taeniurops meyeni, Sphyrna lewini, Carcharhinus galapagensis, Triaenodon obesus, and Galeocerdo cuvier) showed an increasing trend. Our study suggests that some species like S. lewini may be shifting their distributions towards deeper waters in response to ocean warming but may also be sensitive to low oxygen levels at greater depths. These findings highlight the need for regional 3D environmental information and long-term deepwater surveys to understand the extent of shark and ray population declines in the ETP and other regions, as most fishery-independent surveys from data-poor countries have been limited to relatively shallow waters.

Fishing effort dynamics around the Galápagos Marine Reserve as depicted by AIS data

The waters around the Galápagos Marine Reserve (GMR) are important fishing grounds for authorized artisanal vessels fishing within the reserve as well as for national and foreign industrial fleets operating in the wider Ecuadorian Insular Exclusive Economic Zone (IEEZ). Although it was not originally designed for fisheries management, Automatic Identification System (AIS) data provides useful, open access, near real-time and high-resolution information that allows for increased monitoring, particularly around Marine Protected Areas (MPAs) and in Areas Beyond National Jurisdiction. This study uses AIS data provided by Global Fishing Watch to assess the spatial distribution and seasonal dynamics of fishing effort by vessel flag within the GMR and the IEEZ from 2012 to 2021. Based on kernel density estimation analysis, we determinate the core-use areas (50%) and spatial extent (95%) of fishing activities by fleets (Ecuadorian and foreign), gear types and seasons (warm, from December to May; and cold, from June to November). Our results show that the Ecuadorian fleet recorded the most observed fishing hours in the study area, with 32,829 hours in the IEEZ and 20,816 hours within the GMR. The foreign flags with the most observed fishing hours in the IEEZ were Panama (3,245 hours) and Nicaragua (2,468.5 hours), while in the GMR were the 'Unknown flag' (4,991.4 hours) and Panama (133.7 hours). Vessels fished employing different fishing gears, but the waters of the GMR and IEEZ were mostly targeted by tuna purse-seiners and drifting longlines. The spatial distribution of the fishing effort exhibits marked seasonal variability, likely influenced by seasonal migrations of target species such as tunas (e.g., Thunnus albacares, T. obesus and Katsuwonus pelamis), marlins (e.g., Makaira nigricans) and sharks (e.g., Alopias pelagicus). The collection and use of this type of spatial and seasonal information is an essential step to understand the dynamics of fishing activities in national waters and improve fisheries management, particularly in less studied areas and fisheries.

Comparing Seamounts and Coral Reefs with eDNA and BRUVS Reveals Oases and Refuges on Shallow Seamounts

Seamounts are the least known ocean biome. Considered biodiversity hotspots, biomass oases, and refuges for megafauna, large gaps exist in their real diversity relative to other ecosystems like coral reefs. Using environmental DNA metabarcoding (eDNA) and baited video (BRUVS), we compared fish assemblages across five environments of different depths: coral reefs (15 m), shallow seamounts (50 m), continental slopes (150 m), intermediate seamounts (250 m), and deep seamounts (500 m). We modeled assemblages using 12 environmental variables and found depth to be the main driver of fish diversity and biomass, although other variables like human accessibility were important. Boosted Regression Trees (BRT) revealed a strong negative effect of depth on species richness, segregating coral reefs from deep-sea environments. Surprisingly, BRT showed a hump-shaped effect of depth on fish biomass, with significantly lower biomass on coral reefs than in shallowest deep-sea environments. Biomass of large predators like sharks was three times higher on shallow seamounts (50 m) than on coral reefs. The five studied environments showed quite distinct assemblages. However, species shared between coral reefs and deeper-sea environments were dominated by highly mobile large predators. Our results suggest that seamounts are no diversity hotspots for fish. However, we show that shallower seamounts form biomass oases and refuges for threatened megafauna, suggesting that priority should be given to their protection.