Research to identify demographic and evolutionary units of the yellownose skate (Zearaja chilensis) and the roughskin skate (Dipturus trachyderma) between the regions of Valparaiso (33° S) and Magallanes (53° S), Chile
Zearaja chilensis and Dipturus trachyderma are the most commercially valuable batoids that inhabit the continental slope of southern South America from Uruguay (south-western Atlantic Ocean) to central Chile (south-eastern Pacific Ocean) and to the east of the Falkland Islands. The first recorded landings of Z. chilensisin Chile were made in the early 1970s. Since then, the catch effort for both species has gradually intensified especially in the small-scale coastal fleet located between Valdivia (40°S) and Aysen (45° S), which is considered an artisanal fishery by local management authorities and as by-catch in two industrial trawl fisheries: the southern hake Merluccius australis fishery and the common hake Merluccius gayi (Guichenot 1848).
Resilience to fishing pressure varies among skate species. Some populations have decreased dramatically and others have not. In some cases, other have increased because of reorganization of ecological niches. The vulnerability of batoid populations is mostly assessed through the examination of fisheries catch trends, but in many South American countries, including Argentina, Brazil and Chile, skates and rays have generally been recorded as a single unidentified category (e.g. rays, including rajoids and Myliobatiformes) in official fisheries records for several decades. From 2003, however, landings of the target species, the yellownose skate Zearaja chilensis (Guichenot 1848) and the roughskin skate Dipturus trachyderma (Krefft & Stehmann, 1975) and by-catch (a combination of six other skate species) in the Chilean skate fishery have been recorded separately.
This project on Chilean skates focuses on the use of genetics to identify population structure, and how that information can be used in new ways to investigate the extent of the movement and interbreeding between populations. New ways of producing connectivity estimates of movement and interbreeding across different data-types fine-tune fisheries models and promotes further collaboration and mutual understanding between geneticists and fisheries scientists.
The objectives are
- Perform a literature review focussing on the identification of evolutionary and demographic units in cartilaginous fishes.
- Design and evaluate a general sampling plan, which is temporally and geographically appropriate, to achieve the following objectives.
- Genetically identify and characterize the main evolutionary units of the yellownose and roughskin skate along the Chilean coast.
- Genetically identify and characterize the main population units of yellownose and roughskin skate present along the Chilean coast.
- Estimate the number of sources (eg. spawning and nursery grounds) and their relative contribution to each demographic unit in the main capture zone.
Leader: Julio Lamilla, Instituto de Ciencias Marinas y Limnológicas, Universidad Austral de Chile.
Co-investigators: Jennifer Ovenden, Carolina Vargas-Caro, Michael Bennett, Carlos Bustamante
Funding body: Council of the Fisheries Research Fund, Chilean Government