cat gordon & john richardson 2015 skate
DESCRIPTION
Skate populations in the Southwest Cat Gordon and John RichardsonThe Shark Trust, Plymouth, UKE: [email protected]; [email protected] The waters surrounding England’s Southwest present an array of hydrographic regimes, bathymetry and substrate: from the shallow, muddy Severn Estuary to deeper continental shelf and slope waters of the Celtic Sea. The diversity of habitat created by these environmental variables hosts an equally impressive diversity of skate species, ranging from the enigmatic, large-bodied White Skate Rostroraja alba (max TL ~200cm) to the more diminutive Cuckoo Ray Leucoraja naevus (max TL 75cm). Often overlooked in favour of their more charismatic shark relatives, skate occupy key roles within the Southwest’s marine ecosystems. At the same time, skate have long been an important component within commercial fisheries, where they are caught using a variety of gear and continue to be landed into ports throughout the region. As a group, skate demonstrate a mixed resilience to commercial fisheries – although, as with all chondrichthyans, a suite of conservative biological traits make them significantly more vulnerable to over-exploitation. This is reflected in conservation status, with some larger-bodied species assessed as Critically Endangered, while those exhibiting reproductive rates more able to sustain fishing mortality are listed as Least Concern. In this talk, the Shark Trust will describe skate assemblage in Southwest waters, with a focus on distribution and abundance. Species’ varied roles and behaviour within the marine ecosystem will be discussed, as will differing vulnerability to fishing mortality. The extent of commercial fisheries will be outlined, including the relatively recent emergence of fisheries management. Finally, the Shark Trust’s involvement in the move towards more sustainable, managed fisheries will be covered, as will the Trust’s projects designed to raise public awareness of this often neglected group.TRANSCRIPT
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Skate populations in
Southwest waters
Cat Gordon John Richardson
Blo
nd
e R
ay
Sa
lly S
ha
rro
ck
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When is a shark a ray?
When is a ray a skate?
Oviparous
Demersal predators ecosystem balance
Prey on crustaceans, invertebrates, small bony fish
Habitat preference generally soft substrates (sand/mud) but some prefer rocky substrate
Ju
ve
nil
e s
ka
te &
ca
tsh
ark
s
La
ure
n S
mit
h
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16 species reported in British waters
Additional sp. rarely encountered
High diversity in SW ~11 species
Un
du
late
Ra
y
Ca
t G
ord
on
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An Identification guide to the Sharks, Skates, Rays & Chimaeras of the British Isles The Shark Trust. Illustrations Marc Dando.
www.sharktrust.org/id
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An Identification guide to the Sharks, Skates, Rays & Chimaeras of the British Isles The Shark Trust. Illustrations Marc Dando.
www.sharktrust.org/id
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K-selected
Site fidelity Regional populations
Static life-history phase Great Eggcase Hunt
Broad distribution
Relative abundance
Sp
ott
ed
Ra
y
Ca
t G
ord
on
Eggcase hunting sghaywood
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Life history: vulnerablity to overfishing
Morphology: vulnerability to fishing gear Populations take longer to recover
Non-existent PR
Conservation status IUCN report (Dulvy et al. 2014*) Skates, rays and shark-like rays experienced greatest
declines and are most at threat
*Dulvy et al. 2014. Extinction risk and conservation of the worlds sharks and rays. Elife, 3, e00590
Sp
ott
ed
Ra
y
Ca
t G
ord
on
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Change in catch composition
Previously went unnoticed as historically not landed by species but by skate and ray
Populations of large-bodied species depleted
Smaller, more fecund species more abundant
2006 Seafish Skate & Ray Group convened
Species specific landings
Th
orn
ba
ck
Ra
y
Pa
ul
Naylo
r
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o Commercial species
o Mixed fisheries
o North Devon
o Decrease in landings
o Reporting
skate fisheries in the Southwest
Sutton Harbour, Plymouth John Richardson
all illustrations Marc Dando
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commercial landings: 2012
Western English Channel Division VIIe
457.9 t
Blonde Ray 170.2t
Thornback Ray 124.5t
Cuckoo Ray 79.6t
Spotted Ray 44.5t
Small-eyed Ray 29.9t
Sou
rce:
STE
CF
t
= to
nn
es li
ve-w
eigh
t
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commercial landings: 2012
Bristol Channel Division VIIf
705.6 t
Thornback Ray 256.2t
Blonde Ray 215.7t
Small-eyed Ray 175.3t
Sou
rce:
STE
CF
t
= to
nn
es li
ve-w
eigh
t
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commercial landings: 2012
119.6 t
Thornback Ray 34.7t
Small-eyed Ray 29.1t
Cuckoo Ray 18.5t
Blonde Ray 18.2t
Shagreen Ray 10.3t
Spotted Ray 6.6t
Celtic Sea North Division VIIg
Sou
rce:
STE
CF
t
= to
nn
es li
ve-w
eigh
t
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commercial landings: 2012
Celtic Sea South Division VIIh
87.7 t
Cuckoo Ray 63.1t
Shagreen Ray 19.0t
Sou
rce:
STE
CF
t
= to
nn
es li
ve-w
eigh
t
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o TACs and Quotas
o Data Limited Stocks
o Reporting
o Prohibited Species
Cuckoo Rays on fish-market Shark Trust
fisheries management
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o Pragmatic approach
o UK
o EU
o Industry
o Fisheries Advisories
o ID materials
Stornoway Andrew Bennett
Shark Trust engagement in skate fisheries
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thanks for listening
www.sharktrust.org