California’s cryptic angels
Massiel is something of a squatinid sleuth, aiming to decipher whether the Northeast Pacific’s only angel shark species – the Pacific angel shark – has a cryptic, endemic (found nowhere else in the world) counterpart in the Gulf of California. Using mitochondrial DNA and genetic analyses, Massiel hopes to look at differences in Pacific angel sharks from the Gulf of California, and Baja California, and to look at the genetic structure of the population within the Gulf. Doing so is key understanding whether special management is required, especially since the long-lived, slow-growing Squatinidae (angel sharks) are susceptible to overfishing and extinction.
Massiel Alfonso González
A love for the sea and its creatures has been part of me ever since I can remember. I grew up on an island, very close to the coast, and as a child I adored diving with my father and seeing for myself the wonders of the underwater world. As time went by, my interest in the mysteries of the sea increased and prompted me to become a biologist. While studying for my Bachelor’s degree in biology at the University of Havana in Cuba, I began to research population genetics and its application to the conservation of waterbirds. The...
Phylogeography of Pacific Angel Shark (Squatina californica) in Northeastern Pacific: understanding evolution for prioritizing conservation
To test how Pacific angel sharks from the Gulf of California and from the western coast of Baja California differ genetically and morphologically and to evaluate the genetic diversity and phylogeographic structure of these angel sharks in the Gulf of California.
The Pacific angel shark Squatina californica is the only squatinid that occurs in the north-eastern Pacific, but some studies suggest that populations from the Gulf of California constitute a cryptic endemic species. This project aims to clarify this taxonomic issue and will also evaluate the species’ genetic diversity and phylogeographic structure. This information will be important in defining evolutionarily significant units that require special attention for conservation, as well as units that could potentially be managed for sustainable fishing.
Although Squatina californica is the only angel shark species that occurs in the north-eastern Pacific, morphological, reproductive and genetic studies suggest that the population inhabiting Mexico’s Gulf of California differs from the populations in the rest of the species’ range. However, the areas sampled by these studies were limited and not enough evidence was explored to demarcate accurately the species’ boundaries. In addition, it is interesting to test to what extent the temporal and spatial oceanographic variations that characterise the Gulf of California have affected the differentiation of its population. To this end, the gulf has been divided into four eco-regions – open gulf, lower gulf, islands and upper gulf – based on their ecological diversity. This diversity has led to genetic differentiation in benthic species, including elasmobranchs. The Pacific angel shark is classified as Near Threatened on the IUCN’s Red List of Threatened Species, but some authors have emphasised the high extinction risk of members of the Squatinidae family, given their morphology and life history (slow growth, late sexual maturity at about 10 years, long gestation period and limited dispersal). Also playing a role is the fact that their shallow and mainly coastal demersal habitats are increasingly being altered and degraded as a result of anthropogenic pressures. In addition, squatinids are heavily exploited, with hundreds of tons having been caught between 2005 and 2016.
- To test whether Pacific angel shark populations from the Gulf of California and from the western coast of Baja California are genetically and morphologically different by analysing mitochondrial DNA control region (mtDNA-CR) sequences and morphological measurements.
- To evaluate the species’ genetic diversity and to test phylogeographic hypotheses about Pacific angel sharks in the Gulf of California, also by analysing mtDNA-CR sequences.
RESULTS:
Pacific Angel shark represent an important component of the region’s fisheries. This species is cataloged according to the IUCN as Near Threatened with considerable decreases in its population size (Cailliet et al., 2020). The results obtained reveal marked genetic differences between both regions (GC vs PBC), which, together with the reproductive and morphological differentiation that have been reported in previous studies, might support the distinction of two management and conservation units: Gulf of California and Northeast Pacific.