Review of the Diversity, Ecology, and Conservation of Elasmobranchs in the Azores Region, Mid-North Atlantic

Abstract

A vulnerable species group, such as, the elasmobranchs, in a data-deficient context presents a complicated management problem. Evidence suggests that the Azores islands, a remote archipelago on the Mid-Atlantic Ridge, serve essential functions in the life-history of species across taxa. The diversity of marine resources within its EEZ are exploited by local to international fleets, and the full extent of fishing pressure can often be underestimated. Although sharks and rays appear to be of minor importance in the fishery, the possibilities of illegal, unreported, and unregulated fishing raises concerns about these threatened species. However, this group has failed to attract management attention, visible in the lack of regional studies focused on biodiversity, ecology, or threats of elasmobranchs. Our work attempts to review and update the information on elasmobranchs of the Azores and identify potential threats, mainly by the local fisheries. We aim to highlight knowledge gaps that require further research and conservation actions. We (1) update the annotated checklist of elasmobranch species, (2) compare species distribution across a biogeographically similar section of the North Atlantic, and (3) analyze the interaction of elasmobranch species with local fisheries. We confirm 61 chondrichthyan species for the Azores (39 sharks, 17 rays, and 5 chimaeras), adding 19 species to the previous annotated checklist of 1997. The Azores elasmobranch species assemblage most resembles Madeira, the neighboring Macaronesian archipelago. Biogeographic affinities between the chosen regions of the North Atlantic are reflected in the taxonomic structure of families. Although underestimated in the local fisheries, elasmobranchs constitute a regular but highly variable portion of total landings. Misreporting and misidentification is perhaps the greatest concern in the local fisheries records, further aggravated by few existing catch regulations for elasmobranchs. Local knowledge indicates that the Azores serves as essential habitat for at least a few species in coastal areas and shallow seamounts, and potentially so for a number of deep-sea elasmobranchs. The intersection of fishery threats and local essential habitat functions around the archipelago warrants greater research effort and studies.

The Azores: A Mid-Atlantic Hotspot for Marine Megafauna Research and Conservation

“…Large bony and cartilaginous fishes are another key component of the megafauna ensemble occurring in the region, including six tropical and temperate tuna, five billfishes/spearfishes, five sun/moon fishes, three large groupers (one endemic to Macaronesia) and over 60 species of benthic and pelagic sharks and rays (Porteiro et al, 2010;Das and Afonso, 2017) (Table 1). In the case of tuna/billfishes and pelagic/deepsea sharks, this represents a relatively high diversity (e.g., Das and Afonso, 2017).…”

“…Large bony and cartilaginous fishes are another key component of the megafauna ensemble occurring in the region, including six tropical and temperate tuna, five billfishes/spearfishes, five sun/moon fishes, three large groupers (one endemic to Macaronesia) and over 60 species of benthic and pelagic sharks and rays (Porteiro et al, 2010;Das and Afonso, 2017) (Table 1). In the case of tuna/billfishes and pelagic/deepsea sharks, this represents a relatively high diversity (e.g., Das and Afonso, 2017). Some are mostly visitors during the warmer season, i.e., June to November (e.g., tropical tuna and billfishes, mobulid rays, whale shark), but others apparently use the area throughout their lives (e.g., groupers, several deepwater sharks, Afonso et al, 2011;Reid et al, 2019) or as a long-term nursery ground for juvenile growth (e.g., blue, smooth hammerhead and tope sharks, Afonso et al, 2014b).…”

First record of the opal chimaera, Chimaera opalescens (Holocephali: Chimaeridae) and revision of the occurrence of the rabbitfish Chimaera monstrosa in the Azores waters

“…Given the remoteness of the Azores archipelago, the great depths that surround it, the fact that C. monstrosa primarily occupies the upper slope and the high degree of misidentification in past records leads to the conclusion that the second scenario is more plausible. This study therefore suggests the replacement of C. monstrosa with C. opalescens in the checklist of elasmobranchs for Azores given by Das and Afonso (2017), with a total number of four confirmed Chimaera species reported for the region. In the Azores, because of the ban on trawling and low capture of chimerids using baited hooks, the populations of these vulnerable species (i.e., long life span and late maturation) are less susceptible to fishing, an important aspect for the conservation of these species in the region.…”

Small-scale fishers’ perception of the implementation of the EU Landing Obligation regulation in the outermost region of the Azores

“…Handlining provides higher flexibility and adaptability to fishing conditions than longlining. Deep-water sharks are rarely caught with handlines and are more likely to survive after release, which is positive in terms of conservation given the high vulnerability of those species (Das and Afonso, 2017;Garcia et al, 2008). From an economic perspective, the advantages of converting to handlining are reduced costs (employment/crew, bait, number of hooks, fuel, etc.)…”