11th ICRS Abstract book - Nova Southeastern University

Oral Mini-Symposium 10: Ecological Processes on Today's Reef Ecosystems
10-53
Does Behaviour Mediate The Costs And Benefits Of Fast Growth? An Example in A
Marine Fish, pomacentrus Amboinensis
Corinna VON KUERTHY 1 , Mark MEEKAN* 2 , Mark MCCORMICK 3
1 University of Kiel, Kiel, Germany, 2 Darwin Office, Australian Institute of Marine
Science, Brinkin, Australia, 3 School Marine and Tropical Biology, James Cook
University, Townsville, Australia
Body size is a central determinant of survival, fecundity and competitive ability. Fast
growth, resulting in large body size, can be beneficial so we might expect that individuals
that are capable of maximising growth to attain the greatest body size will be favoured by
selection. However, in the field, maximal growth is found only rarely. It has been
suggested that trade-offs between the costs and benefits of growth are mediated by
behaviour, whereby rapid growth is associated with greater predation mortality due to
increased foraging effort. Here, test this hypothesis by examining the behaviour, growth
and survivorship of a common reef fish, Pomacentrus amboinensis at Lizard Island on
the Great Barrier Reef (GBR) during the first month of settlement on the reef. We
collected young fish using light traps settled them onto small artificial reefs where their
behaviour and survivorship was monitored for 24 hrs. One month later individuals of the
same cohort were collected from shallow reefs and distributed on the same artificial reefs.
Their behaviour and survivorship was monitored for 6 d. Size-at-age and growth rates of
surviving fish in both experiments were reconstructed using the records stored within the
otoliths or earbones of the juvenile fish. At settlement young fish suffered high mortality
that preferentially removed larger, faster-growing individuals. However, we could not
find any evidence that the foraging behaviour of these larger fish contributed to this
pattern of selective mortality. In contrast, one month after settlement the same cohort of
fish underwent negative size selective mortality where the smallest, slower-growing fish
were preferentially removed by predators. Larger fish spent more time foraging and were
more aggressive than smaller individuals. These results are discussed in the context of
current views of the role of behaviour in mediating patterns of selective mortality in prey
species.
10-54
Microhabitat Specialisation, Recruitment And Coral Decline: Population Responses
in Two Coral Reef Fish Families
Maya SRINIVASAN* 1 , Geoffrey JONES 1 , Mark MCCORMICK 1
1 School of Marine and Tropical Biology, James Cook University, Townsville, Australia
Many marine species are undergoing long-term changes in abundance in response to
habitat degradation. While recruitment is known to be a primary driver of the temporal
and spatial dynamics of coral reef fish populations, its role in determining responses to
habitat change is poorly understood. Here we examined microhabitat use of recently
settled reef fishes in Kimbe Bay (PNG), focussing on family-level patterns for the two
most common reef-associated taxa, the damselfishes (Pomacentridae) and wrasses
(Labridae). We also investigated the influence of microhabitat specialisation at
settlement on temporal patterns in adult abundance following a decline in coral cover.
The majority of species were strongly associated with a narrow range of microhabitats.
Both live branching corals (particularly Acropora and Pocillopora spp.) and dead
substrata were preferred recruitment microhabitats for different species. A decline in
coral cover between 1997 and 2002 resulted in population declines of 75% of the
common reef fish species. Wrasses exhibited the greatest range of responses, including
increases, declines and stable populations, while the majority of damselfish species
declined. The magnitude and direction of the long-term change in fish abundance was
inversely correlated with the degree of association between recruits and live branching
corals. For a given level of live coral dependence, the magnitude of decline was greater
among the damselfishes than the wrasses. This may be explained by a comparison of
recruit-adult relationships among species and between the two families, which
established that a given average density of recruits resulted in greater average densities of
adult damselfishes, compared with wrasses. The family-level differences between
damselfish and wrasses may reflect fundamental differences in their life history traits,
reliance on living corals and the carrying capacities of the habitat.
10-55
Is Bigger Really Better? Investigating The Size Selectivity Of Predation On Newly Settled
Coral Reef Fishes
Thomas HOLMES* 1,2 , Mark MCCORMICK 1,2
1 School of Marine and Tropical Biology, James Cook University, Townsville, Australia,
2 Australian Research Council Centre of Excellence for Coral Reef Studies, Townsville,
Australia
Recent evidence suggests that the early post-settlement period of coral reef fishes may be
critical in determining the size and structure of adult fish populations. Predation by small site
associated predators has been shown to be responsible for a majority of mortality during this
period, and the relative body size of predator and prey is generally regarded as one of the most
important characteristics influencing the outcome of such events. This study investigated the
size selectivity of four predator species known to be responsible for a majority of predation on
early post-settlement reef fishes at Lizard Island, northern Great Barrier Reef, Australia.
Additionally, it examined how size selectivity changed with predator ontogeny. Using
aquarium based predator trials, selectivity was examined for both the size range of prey at the
time of settlement, and for the size range over the early juvenile period immediately following
settlement. The intensity and direction of size-selection was found to differ greatly between the
predator species. During the ‘settlement stage’ trials, distinctive preferences towards either
large or small prey size classes were observed for some predator species, whilst others were
more ‘generalist’ in their prey choice. During ‘early juvenile’ trials all predator species
generally chose smaller size classes, although the intensity of this selection varied. Selectivity
was not found to differ with changing predator body size. This research shows that larger size
at the time of settlement does not necessarily convey a survival advantage during predatory
interactions. However, larger size does become a clear advantage as an individual passes into
the early juvenile stage. These selective patterns are thought to be driven by a combination of
prey behaviour, and species specific predator behaviours, predation modes and gape size.
10-56
Carry-Over Effects – The Importance Of A Good Start
Mark MCCORMICK* 1 , Monica GAGLIANO 1
1 Marine and Tropical Biology, James Cook University, Townsville, Australia
Complex life cycles are common in marine organisms and success at each life stage depends
upon individuals exhibiting the best series of performance traits to meet the challenges of their
current environment. High performance in one stage does not guarantee success in another.
Despite the potential for conflicting selective forces on sequential life stages, recent evidence
emphasizes the importance of interconnections between survival traits among life stages. This
presentation reviews recent studies of carry-over effects for marine fishes and emphasizes the
overwhelming importance of previous growth history in biasing later survival and reproductive
success. Research also stresses the importance of non-genetic maternal effects in affecting
offspring success.
86