Biscuit Skate

(Raja straeleni)

Biscuit, skate

Species is currently under revision.

1. What is it?

Biscuit skates (Raja straeleni) are long-lived, slow growing, cartilaginous fish. They tend to mature quite late and have a low fecundity making them susceptible to over fishing. There is no directed fishery for skates; they are commonly caught as bycatch. No stock assessment has been done on them but there are some indications of that they are being over fished due to declines in catch abundances.

2. How was it caught or farmed?

Inshore demersal trawl

Biscuit skates are caught as bycatch in inshore demersal trawl fishery (hake and sole) using trawl nets. In the inshore zone, trawl nets are dragged along the sea bed at depths in the area from the coast to the 110 m isobath or to 20 nautical miles from the coast, whichever is the greater distance. The offshore zone is defined as offshore of this inshore zone; inshore trawl sector vessels are also permitted to fish in the offshore zone although they are limited in actuality by vessel size/power. Demersal trawling is known to damage the seabed; the extent and impact of this damage remains unknown. This methodology is not selective, however, and a number of other benthic species are often caught in the nets as well. Seabird bycatch was highlighted as an issue and the subsequent introduction of tori lines (lines covered in coloured streamers making attachment lines more visible to birds) has led to a decrease in bird mortalities.

Offshore demersal trawl

Biscuit skates are caught as bycatch within the within the offshore demersal trawl industry for hake (MSC certified) using trawl nets that are dragged along the sea bed at depths typically ranging from 110 m to 800 m (known as “demersal trawl nets”). This type of trawling is known to damage the seabed; the extent and impact of damage remains unknown. Trawling is not a very selective fishing method and a number of other species are often caught in the nets (fish, sharks and rays). Sea bird interactions with trawl cables near the surface are also a major concern. A success story in the fishery has been the implementation of effective seabird mitigation strategies developed in connection with the MSC-certification process. These strategies have resulted in a dramatic reduction in sea bird-fishery interactions through the introduction of tori lines (lines covered in coloured streamers making attachment lines more visible to birds) and improved disposal of offal (discard that attracts seabirds).

3. Where is it from?

Inshore demersal trawl

Biscuit skates are caught between Cape Agulhas and the Great Kei River at depth shallower that 110 m. Management is considered to be partly effective. Management is mainly directed at the target species (hake and sole) in the form of Total Allowable Catch (TAC) and permit limitations. Some ecosystem-based management measures have been implemented, such as the use of tori lines to minimize seabird interactions and limited fishing areas. There is a fishery conservation project ( FCP ) presently underway seeking to test a co-management approach that would bring under management 10 non-target species in the sector. Additional ecological concerns are little information on impacts to sensitive shark, skates and ray populations as well as impacts to the seabed. Efforts are underway to improve the scientific observer coverage at sea for this sector to better understand ecosystem impacts.

Offshore demersal trawl

Biscuit skates are caught as bycatch on the continental shelf edge and upper slope along the West Coast from the Namibian border southwards and on the South Coast primarily around the Agulhas Bank. Management is mainly focused on (hake) in the form of Total Allowable Catch (TAC) and permit limitations. There are some ecosystem-based management measures in place such as precautionary catch limits on monkfish and kingklip, tori lines to reduce sea bird interactions, and limited fishing areas (i.e. fishing within a “footprint” to limit seabed disturbance). Research is underway to better understand impacts to seabed habitats. There is however, little information on impacts to sensitive shark, skate and ray populations.