TY - JOUR
T1 - Ontogenetic variation in movements and depth use, and evidence of partial migration in a benthopelagic elasmobranch
AU - Thorburn, James
AU - Neat, Francis
AU - Burrett, Ian
AU - Henry, Lea-Anne
AU - Bailey, David M.
AU - Jones, Cath S.
AU - Noble, Les R.
N1 - The Marine Alliance for Science and Technology for Scotland (MASTS) provided funding via a Ph.D. studentship and through the community project SIORC (Sharks, skate, and rays in the offshore and coastal regions of Scotland). MASTS was funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. This work was supported by the Fisheries Society for the British Isles and Scottish Natural Heritage.
PY - 2019/9/25
Y1 - 2019/9/25
N2 - Tope (Galeorhinus galeus) is a highly mobile elasmobranch in the
temperate to subtropical northeast Atlantic. It is highly migratory and
has been shown to display complex movement patterns, such as partial
migration, in the southern hemisphere. In the northeast Atlantic,
previous mark-recapture studies have struggled to identify movement
patterns and the species behavior is poorly described, yet
identification of migratory behaviors and habitats of importance for the
species is of paramount importance for effective management. Here, we
combined fisheries independent survey data with mark-recapture (MR) data
to investigate the distribution of different age classes of tope across
the northeast Atlantic. We further investigated depth use in detail
with archival electronic tags and a pop-up satellite archival tag
(PSAT). We suggest previous studies struggling to find consistent
movement patterns using MR data were confounded by a combination of site
fidelity, partial migration by females, and increasing depth and home
range of juveniles. Survey and MR data showed immature tope <40 cm
were caught exclusively in continental shelf waters <45 m deep,
showing a significant relationship between habitat depth and total
length. Immature individuals seemed to remain on the continental shelf,
while mature tope of both genders were caught in both shelf and offshore
waters. This use of deeper water habitats by mature tope was further
supported by archival tags, which indicated individuals use both shallow
(<200 m depth) and deep-water habitats, diving to depths of 826 m;
the deepest record for this species. The PSAT tag tracked the horizontal
movements of an adult male, which confirmed utilization of both shallow
inshore and deep offshore habitats. Most tope remained within 500 km of
their tagging site, although some mature females had a larger, more
southerly range, including connectivity with the Mediterranean. This
study clearly demonstrates the highly migratory habits of tope, and
suggests larger individuals divide their time between shallow and
deep-water habitats. It shows the northeast Atlantic tope population
should benefit from consistent management throughout its range.
AB - Tope (Galeorhinus galeus) is a highly mobile elasmobranch in the
temperate to subtropical northeast Atlantic. It is highly migratory and
has been shown to display complex movement patterns, such as partial
migration, in the southern hemisphere. In the northeast Atlantic,
previous mark-recapture studies have struggled to identify movement
patterns and the species behavior is poorly described, yet
identification of migratory behaviors and habitats of importance for the
species is of paramount importance for effective management. Here, we
combined fisheries independent survey data with mark-recapture (MR) data
to investigate the distribution of different age classes of tope across
the northeast Atlantic. We further investigated depth use in detail
with archival electronic tags and a pop-up satellite archival tag
(PSAT). We suggest previous studies struggling to find consistent
movement patterns using MR data were confounded by a combination of site
fidelity, partial migration by females, and increasing depth and home
range of juveniles. Survey and MR data showed immature tope <40 cm
were caught exclusively in continental shelf waters <45 m deep,
showing a significant relationship between habitat depth and total
length. Immature individuals seemed to remain on the continental shelf,
while mature tope of both genders were caught in both shelf and offshore
waters. This use of deeper water habitats by mature tope was further
supported by archival tags, which indicated individuals use both shallow
(<200 m depth) and deep-water habitats, diving to depths of 826 m;
the deepest record for this species. The PSAT tag tracked the horizontal
movements of an adult male, which confirmed utilization of both shallow
inshore and deep offshore habitats. Most tope remained within 500 km of
their tagging site, although some mature females had a larger, more
southerly range, including connectivity with the Mediterranean. This
study clearly demonstrates the highly migratory habits of tope, and
suggests larger individuals divide their time between shallow and
deep-water habitats. It shows the northeast Atlantic tope population
should benefit from consistent management throughout its range.
KW - Tope
KW - School shark
KW - Depth range
KW - Archival tags
KW - Migration
KW - Site fidelity
U2 - 10.3389/fevo.2019.00353
DO - 10.3389/fevo.2019.00353
M3 - Article
SN - 2296-701X
VL - 7
JO - Frontiers in Ecology and Evolution
JF - Frontiers in Ecology and Evolution
M1 - 353
ER -