After a short recess, the benthic catshark
tag and release program is up and running again! This year we have added an
additional two sites to the sampling protocol, namely: Santos and Darwin.
Since August 2012 we have tagged a total of
17 catsharks: Leopard = 1, Pyjama Jacket = 3 and Puffadder = 13. Unfortunately,
with no recaptures yet, however, there are possible reasons for this. Negatives:
(i) the tag may have fallen off – any scars would likely have healed as sharks
have incredible regenerative capabilities, (ii) tagged sharks have died due to natural
predation, or alternatively have been caught by fishermen and killed - as they
are considered a pest species. Positives: (i) these sharks are abundant and there
is a low probability of capturing the same individual more than once. Let’s
hope it’s the latter!
Although most species of catshark occurring
in Mossel Bay are endemic to South Africa, despite their relative abundance –
information is still limited. This tag and release project therefore represents
an effective, low cost tool to obtain vital information on these little studied
species.
This research project aims to investigate the
following key questions relating to the biology and ecology of these endemic
sharks:
i.
Diversity of benthic catsharks
in Mossel Bay reef systems
ii.
Degree of spatial variation in
benthic catshark composition between Mossel Bay reef systems
iii.
Population composition and
abundance of benthic catsharks sampled in Mossel Bay
The insight gained
from this study will contribute to a more comprehensive understanding about the
role these catsharks play in community dynamics. These benthic sharks likely
represent predators within their micro-scale habitats and are thus considered
to have top-down predatory effects at the community level at which they occur.
Furthermore,
most of these catsharks are listed as Near Threatened on the IUCN Red
List of Threatened Species – prioritising them as species of conservation
concern!!
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