%0 Thesis
%A Martins, Camila Leite
%D 2017
%T Stress, survival and movement following fishing gear capture in chondrichthyan species
%U https://bridges.monash.edu/articles/thesis/Stress_survival_and_movement_following_fishing_gear_capture_in_chondrichthyan_species/5462446
%R 10.4225/03/59d2c61dbc548
%2 https://ndownloader.figshare.com/files/9446269
%K Fisheries capture
%K handling
%K air exposure
%K physiological stress
%K secondary stress response
%K blood chemistry
%K acoustic tag monitoring
%K post-release fate
%K movement
%K immediate mortality
%K delayed mortality
%X Fishing procedures
involve capture in fishing gear, subsequent handling and exposure to air (for
discarded animals), which can cause physical damage, asphyxiation, stress,
physiological changes and lead to mortality, depending on the magnitude of the
stress. The first objective of the present study was to investigate the effects
of fishing (capture, handling and air exposure) on a target, byproduct
(retained non-targeted) and bycatch (discarded) species of Australian
chondrichthyans, and assess their post-release survival or mortality. The
target and byproduct species were gummy shark (Mustelus antarcticus) and
elephant fish (Callorhinchus milii), and the bycatch species was southern
fiddler ray (Trygonorrhina dumerilii). Capture in different fishing gears for
various periods was simulated under laboratory conditions and physiological
changes were measured through repeated blood sampling. The animals’
post-release fate was determined in captivity during a 72-h blood monitoring
period for all species and in the wild for gummy sharks and southern fiddler
rays tagged with acoustic transmitters. The acoustic monitoring data gained
with telemetry was also used to investigate these species’ movement patterns,
habitat use and long-term fate inside Port Phillip Bay and Swan Bay Marine
Park, which are natural habitats for the gummy shark and southern fiddler ray
populations (neonate, juvenile and adult animals). This was the second
objective of the present study.
The results showed that capture stress and handling caused
physiological changes in all three species. Increases in plasma lactate and
potassium levels and decreases in plasma glucose levels were recorded in
stressed elephant fish. Increases in plasma lactate, glucose and potassium
levels were measured in stressed gummy sharks. Elevated plasma lactate and
glucose levels were recorded in stressed southern fiddler rays. The blood
variables measured immediately after capture did not show the extent of the
physiological responses to capture stress in elephant fish and gummy sharks.
However, plasma lactate levels in southern fiddler rays peaked immediately
after capture and capture with air exposure. Gillnet was the capture gear
causing the greatest stress and mortality in elephant fish and gummy sharks.
Trawl capture caused greatest stress in southern fiddler rays, and air exposure
immediately after trawl capture significantly exacerbated stress-related
physiological changes. Handling alone significantly increased plasma lactate
concentrations in elephant fish and gummy sharks, but not in southern fiddler
rays. Stress from capture, handling and transport significantly increased blood
variable levels and caused irregular short-term movement activities and reduced
area use of three stressed gummy sharks and three stressed southern fiddler
rays tagged with transmitters and released to the wild. Irregular movement may
have increased the chances of two of these gummy sharks being subsequently
recaptured by fishers. Mean area use was not statistically different between
control treatments and capture treatments during the short-term movement for
gummy sharks and southern fiddler rays. Immediate mortality of elephant fish
and gummy shark after capture stress in all gears overall was 0% and 3%,
respectively, and delayed mortality of these species was 25% and 6%,
respectively. No immediate or delayed mortality after stress was recorded in
southern fiddler rays. These post-release survival results suggest that
elephant fish have high sensitivity to capture-stress in fishing gear, gummy
sharks have medium sensitivity and southern fiddler rays have low sensitivity
(resilient) to capture-stress in fishing gear.
Long-term movement patterns and area use varied among gummy
sharks and southern fiddler rays. Gummy sharks used larger areas inside Port
Phillip Bay and Swan Bay than southern fiddler rays. In general, slightly
higher movement and larger area use occurred at night than during the day for
both species, but the differences were not significant. Both species used the
Swan Bay Marine Park, with the gummy sharks using larger areas inside the
marine park than the southern fiddler rays; however, the rays stayed inside the
marine park for longer periods than the gummy sharks. The greatest use areas
for gummy sharks were in the north-western and far southern regions of the
marine park, sharing the latter with the southern fiddler rays. Gummy sharks
preferred sparse seagrass (Zostera and Heterozostera) with associated
filamentous algae inside Swan Bay followed by macroalgae habitat type. Bare
sediment was the habitat type more used inside Swan Bay for southern fiddler
rays followed by medium seagrass (Zostera and Heterozostera) with associated
filamentous algae. No differences in movement patterns, area use and day and
night activities between sexes were observed in gummy sharks and southern
fiddler rays.
The present study provides important physiological, mortality
and movement information for ecological risk assessments from effects of
fishing of these three chondrichthyan species (elephant fish, gummy shark and
southern fiddler ray), aiming to improve management and conservation of their
populations. The study demonstrates that the use of stress-related
physiological changes and acoustic monitoring together is highly effective for
quantifying immediate and delayed mortality caused by fishing capture and
irregular short-term movement patterns after capture. Because blood samples
taken immediately after capture and landing on boats may not show the extent of
the stress-related physiological changes, delayed mortality estimates solely
from one blood sample can be underestimated. Therefore tagging with acoustic
transmitters and release provides supporting information to determine delayed
mortality, area use and movement patterns. The combination of these two
approaches, physiological changes and acoustic monitoring, can facilitate
studies undertaken on boats when animals cannot be held in tanks or pens
following capture to determine their post-release survival.
%I Monash University