true

ISRA FACTSHEETS

SOUTH AMERICAN ATLANTIC REGION

ISRA FACTSHEETS

SOUTH AMERICAN ATLANTIC REGION

Central San Matías Gulf ISRA

55/81

Central San Matías Gulf ISRA

Central San Matías Gulf

Summary

Central San Matías Gulf is located in the Río Negro Province of Argentina. It encompasses the northwest and central part of the semi-enclosed San Matías Gulf. The area is characterised by a continental shelf with depths exceeding 200 m. The area is influenced by two gyres and a thermohaline front enhanced by tides and regional winds. Within the area there are: threatened species, range-restricted species, and undefined aggregations (La Plata Skate Atlantoraja platana).

Central San Matías Gulf

Central San Matías Gulf

DESCRIPTION OF HABITAT

Central San Matías Gulf is located in the Río Negro Province of Argentina. It encompasses the northwest and central part of the semi-enclosed San Matías Gulf. This is the second largest gulf in Argentina and covers 19,700 km2 (Gagliardini & Rivas 2004). The area is characterised by a continental shelf with depths exceeding 200 m (Coller 2012). The area is influenced by two gyres: a cyclonic gyre in the north and an anticyclonic gyre in the south, which drive the inflow of cooler, less saline water from the south and the outflow of warmer, saltier water to the north (Piola & Rivas 1988). From October–March, enhanced by tides and regional winds, a thermohaline front divides the gulf into two areas, with the northern sector having higher salinity and temperature but lower primary productivity (Gagliardini & Rivas 2004).

This Important Shark and Ray Area is benthic and subsurface and is delineated from 50–220 m based on the depth range of Qualifying Species and the bathymetry in the area.

CRITERION A

VULNERABILITY

One Qualifying Species considered threatened with extinction according to the IUCN Red List of Threatened Species regularly occurs in the area. This is the Endangered La Plata Skate (Pollom et al. 2020).

CRITERION B

RANGE RESTRICTED

Central San Matías Gulf holds the regular and predictable presence of the La Plata Skate as a resident range-restricted species.

Historical data indicate that La Plata Skate has a year-round presence in the area and was one of the most frequently landed skate species between 2007–2009 in the San Matías Gulf, accounting for 34.5% of the relative abundance in commercial landings for skates (Estalles et al. 2011). The species completes its entire life cycle within the San Matías Gulf, with all life stages documented (Coller 2012).

Additionally, La Plata Skate is reported from the area based on standardised bottom trawl surveys conducted in the Gulf of San Matías during 10–13 days per year in October, November, or December between 2006–2024 (CONDROS-CIMAS unpubl. data 2025). Sampling was carried out at 43 stations across the entire San Matías Gulf (CONDROS-CIMAS unpubl. data 2025). A bottom trawl net with a 20.5 m upper headline and an internal codend liner with a mesh size of less than 20 mm was used for 30-minute hauls. A total of 499 individuals (51.7%) were captured in the area, out of 965 in the broader region during the study period (CONDROS-CIMAS unpubl. data 2025). Annual captures in the area were documented in 2006 (n = 114 individuals), 2007 (n = 60), 2016 (n = 264), 2018 (n = 54), and 2024 (n = 7) (CONDROS-CIMAS unpubl. data 2025). The number of individuals per set ranged from 1–167 (mean = 19.9). Additionally, in 2022 and 2023, La Plata Skate was also recorded in shrimp fisheries in the area on eight occasions (CONDROS-CIMAS unpubl. data 2025).

La Plata Skate is distributed across the Patagonian Shelf and South Brazil Shelf Large Marine Ecosystems (LMEs). However, it is primarily encountered in the San Matías Gulf within the Patagonian Shelf LME (Estalles et al. 2011; Coller 2012; Sabadin 2018).

CRITERION C

SUB-CRITERION C5 – UNDEFINED AGGREGATIONS

Central San Matías Gulf is an important area for undefined aggregations of one ray species.

Skates are known to aggregate, with temporal changes in aggregations related to sex and life-stage segregations (Swain & Benoît 2006; Frisk 2010; Hoff 2010). Skate aggregations are usually related to high density areas where large catch quantities occur (Bizzarro et al. 2014).

Between 2006–2024, La Plata Skate was captured in aggregations during standardised bottom trawl surveys conducted in the Gulf of San Matías during 10–13 days per year in October, November, or December and monitored by scientific observers onboard the vessels (CONDROS-CIMAS unpubl. data 2025). Trawling surveys lasted 30 minutes using a bottom trawl net with a 20.5 m upper headline and an internal codend liner with a mesh size of less than 20 mm.

La Plata Skate was captured in 116 out of 191 recorded hauls (61%) across the San Matías Gulf, totalling 965 individuals. Most hauls containing La Plata Skate (74%) captured between one and nine individuals, while 30 hauls (26%) reported captures of 10–167 individuals across the entire Gulf. Of these, 13 hauls occurred within the area, that presented the highest aggregation density (based on kernel density analysis), accounting for 43% of hauls with more than ten individuals. From the 499 individuals captured within the area, 469 were recorded within aggregations (haul with more than ten individuals). A total of 13 aggregations were captured ranging from 10–167 individuals (mean= 36; SD= 35.7), in 2006 (n = 4 aggregations), 2007 (n = 2), 2016 (n = 5), and in 2018 (n = 2) (CONDROS-CIMAS unpubl. data 2025).  Further information is needed to confirm the function and nature of these aggregations.

Central San Matías Gulf

SUBMIT A REQUEST

ISRA SPATIAL LAYER REQUEST

To make a request to download the ISRA Layer in either a GIS compatible Shapefile (.shp) or Google Earth compatible Keyhole Markup Language Zipped file (.kmz) please complete the following form. We will review your request and send the download details to you. We will endeavor to send you the requested files as soon as we can. However, please note that this is not an automated process, and before requests are responded to, they undergo internal review and authorization. As such, requests normally take 5–10 working days to process.

Should you have questions about the data or process, please do not hesitate to contact us.

    * indicates required

    Industry or sector (*)

    Under the terms and conditions of our User License Agreement , full and appropriate acknowledgement is required in any materials and publications derived from the data (and copies should be sent to the IUCN SSC Shark Specialist Group through the contact form). For any publications making substantial use of the data, the ISRA welcomes the opportunity for co-authorship, collaboration, and to comment prior to publication.


    Furthermore, we need to know whether you are a commercial or non-commercial user. Non-commercial includes scientific research, education or conservation. Commercial is defined as follows: any use by, on behalf of, or to inform or assist the activities of a commercial entity (that operates ‘for profit’) or use by a non-profit for the purposes of revenue generation

    Type of use(*):

    Please specify which layer (ex. all layers, layers within a specific Region, layers within a Jurisdiction or a single ISRA): Purpose (*):

    Please provide a description of how you intend to use the ISRA GIS Dataset. The more details you provide, the faster we can respond to your request. We may require further clarification prior to providing access. (min. 100 characters – max 1,000 characters)



    File format request (*)

    By providing your personal data, you consent to its processing as described below. The IUCN SSC Shark Specialist Group will use the information you provide on this form to send the documents you requested. You can change your mind at any time by writing to the ISRA Data Coordinator www.sharkrayareas.org/contact. All personal details provided will be treated with respect. For any information you can visit our Privacy Policy.
    Please read the User License Agreement and ISRA Layer Metadata Description

    This form uses Google reCaptcha to reduce spam. Privacy - Terms