Patterns of Research Effort and Extinction Risk of Marine Mammals in the Philippines

Global marine mammal research is disproportionately lacking compared to terrestrial mammal research and is strongly biased toward populations in Europe, North America, New Zealand, and Australia. With high extinction risks facing marine mammals in the tropics, we sought to identify potential drivers of research effort and extinction risk evaluations for marine mammals in the Philippines as a model for tropical island nations with limited resources and research capacity. Using a bibliographic approach, we compiled all materials on marine mammal research in the Philippines from 1991 to 2020, which we categorized into eight thematic areas of research focus. We reviewed all materials based on their research focus to assess the current scientific knowledge of local marine mammal populations. Using a simple metric to calculate research effort allocation, we found that all marine mammal species in the Philippines receive inadequate research attention. Using generalized linear models, we analyzed the relationship of potential factors that drive research effort. The model with the lowest Akaike Information Criterion value suggests that frequency of marine mammal stranding incidents may influence an increase in research effort on marine mammals by providing access to biological specimens that would normally be difficult to obtain. Strandings are unfortunate events with often unclear causes, but they provide an opportunity to collect data from behaviorally cryptic animals in areas where financial constraints often hamper scientific progress. We also determined that a national Red List evaluation was predicted by increased research effort. Maximizing local research using all materials from strandings and building research capacity may be an alternative to expensive field-based methods to increase knowledge on local marine mammal populations

Shore-fish assemblage structure in the central Philippines from shallow coral reefs to the mesophotic zone

Connectivity between shallow coral reefs and adjacent deeper habitats may be crucial to reef ecosystem stability. However, deeper habitats such as mesophotic coral ecosystems (MCEs) remain understudied. We investigated the depth structuring of shore-fish assemblages in the central Philippines across shallow (10-30 m) and mesophotic (upper: 30-60 m, lower: 60-90 m) depth zones. Baited video surveys in two coastal sites similar to 30 km apart showed strong declines with depth in fish species richness and abundance including fishery target species. Corallivores, herbivores/detritivores, omnivores and planktivores showed the strongest declines. Invertivores and generalist carnivores dominated abundance at mesophotic depths. Data from the coastal sites were analysed with published data from an offshore island (Apo Island) < 25 km away to provide broader insights on spatial variability of shore-fish depth structuring. The percentages of species that overlapped shallow and mesophotic depths were much lower in coastal sites (9-13%, 9-11%) than the island (20-26%), suggesting higher potential vertical connectivity in the latter. Mean assemblage similarities (Bray-Curtis) between shallow and mesophotic depth zones were found to be low at all sites (0.3-19.6) and decreased with depth. Fish assemblages gradually differed across depth zones at coastal sites but mesophotic assemblages at the island were more similar to the shallow coastal assemblages. Strong correlations between fish assemblages and benthic habitat were detected, suggesting that higher cover of rocky substratum at mesophotic depths facilitates vertical connectivity at the island. Our findings highlight benthic habitat as a driver of spatial variation in the depth structuring and vertical connectivity of shore-fish assemblages

Half a century of rising extinction risk of coral reef sharks and rays

Sharks and rays are vital coral reef species. This study shows that nearly two thirds (59%) of the 134 coral-reef associated species are threatened with extinction. The main cause of their decline is found to be overfishing, both targeted and unintentional, and extinction risk is greater for larger species found in nations with higher fishing pressure and weaker governance