15 research outputs found
UNDERSTANDING THE RESPONSE OF GROUPERS (EPINEPHELIDS) TO CLIMATE-CHANGE AND FISHING DISTURBANCES IN THE LAKSHADWEEP ARCHIPELAGO, INDIA
Alternative reproductive tactics and inverse size-assortment in a high-density fish spawning aggregation
Coping with catastrophe: foraging plasticity enables a benthic predator to survive in rapidly degrading coral reefs
10 páginas, 7 figuras, 1 tabla, 1 apéndice.Human-induced rapid environmental change (HIREC) disproportionately affects species with specialist
traits and long generation times. By circumventing prolonged evolutionary processes, behavioural
plasticity is critical in allowing species to cope with rapid environmental changes within their lifetimes.
Coral reefs have faced multiple mass mortality events of corals related to climate change in the last two
decades. The consequent loss of structural complexity adversely impacts long-lived, structure-dependent
fish predators. We attempted to determine how well a guild of groupers (Pisces: Epinephelidae) copes
with rapid structural change in the lightly fished Lakshadweep Archipelago, Indian Ocean. Of the 15
species, territorial and site-attached groupers declined exponentially with decreasing structural
complexity, while widely ranging species showed no change. However, one site-attached species, the
peacock grouper, Cephalopholis argus, maintained high densities across the structural gradient. We
explored the mechanisms this species employs to cope with declining habitat structure. Our observations
indicate that both a potential release from specialist competitors and plasticity in foraging behaviour
(foraging territory size, diet and foraging mode) appeared to favour the peacock grouper's survival in
sites of high and low structure. While specialist competitors dropped out of the assemblage, the foraging
territory size of peacock groupers increased exponentially with structural decline, but remained constant
and compact (50 m2) above a threshold of structural complexity (corresponding to a canopy height of
60 cm). Interestingly, despite significant differences in prey density in sites of high and low structure, gut
content and stable isotope analyses indicated that peacock groupers maintained a specialized dietary
niche. In-water behavioural observations suggested that diet specialization was maintained by switching
foraging modes from a structure-dependent ‘ambush’ to a structure-independent ‘widely foraging’
mode. The remarkable foraging plasticity of species such as the peacock grouper will become increasingly
critical in separating winners from losers and may help preserve specialist ecosystem functions as
habitats collapse as a result of climate change.This
study was conducted with funding from Rufford Small Grants
Foundation (grant number 16133-B) and the Pew Marine
Fellowship.Peer reviewe
Wave exposure reduces herbivory in post-disturbed reefs by fltering species composition, abundance and behaviour of key fsh herbivores
Este artículo contiene 14 páginas, 6 figuras, 3 tablas.Harsh environmental conditions limit how species use the landscape, strongly infuencing the way
assemblages are distributed. In the wake of repeated coral bleaching mortalities in Lakshadweep,
we examined how wave exposure infuences herbivory in exposed and sheltered reefs. We used a
combination of i. feld observations of fsh herbivore composition, abundance and activity across 6
exposed and 6 sheltered reefs; ii. experimental manipulations in a subset of these reefs (herbivore
exclosures); and iii. opportunistic observations of fsh recruitment, to determine how exposure
infuences herbivore biomass and herbivory. Species richness, biomass, abundance, total bite rates
and species-specifc per capita bite rates were lower in exposed compared to sheltered reefs, linked
to strong environmental fltering of species composition, abundance and behaviour. For some critical
species, this environmental fltering begins with diferential recruitment and post-recruitment
processes between exposures. Bite rates at sheltered sites were dominated by just a few species, most
being laterally compressed surgeonfsh that may fnd it difcult accessing or surviving in wave-battered
shallow reefs. Exclosure experiments confrmed that exposed reefs were less controlled by herbivores
than sheltered reefs. In post-disturbed reefs like Lakshadweep, environmental gradients appear to be
key mediators of critical functions like herbivory by determining species composition, abundance and
behaviour.This work was funded by Rohini Nilekani Philanthropies (RA, SY, TA, PR), DSTSERB Intramural Grant (EMR/2017/004014), Azim Premji University Research Grant, DBT-RA Fellowship
Program in Biotechnology and Life Sciences (RK) and the Spanish Consejo Superior de Investigaciones
Científicas under the project supported by the Memorandum of Understanding between CEAB (CSIC)-
NCF, Department of Science and Technology and IdeaWild. This research was conducted under permit
F.No.16/11/2014-ADM of the Administration and the Department of Science and Technology, Union
Territory of Lakshadweep.Peer reviewe
Hypothesizing novel mating behaviours in the squaretail grouper based on direct behavioural observations
Historically unfished, high-density spawning aggregations are vanishingly uncommon. Behavioural observations from such aggregations are rare, and may be sometimes novel and unexpected. Given the weight of evidence required to document spawning aggregations, how can we best report rare and unusual behavioural variations in spawning populations? Based on two years of in-water observations of a high-density spawning aggregation of the squaretail grouper in the Lakshadweep Archipelago, we described a previously unreported male alternative reproductive tactic (ART) and an inverse size assortment with large males courting several small females that shoaled mid-water (https://doi.org/10.1186/s12898-017-0120-5). In critiquing our manuscript, it has been suggested that our observations, methodologies and interpretation are inadequate, flawed, and do not fit within currently accepted theory (https://doi.org/10.1186/s12898-018-0206-8). While offering a detailed counter of the main methodological and theoretical criticisms we question how best to document and interpret novel behaviours in poorly known systems. Reporting novelty itself can hardly be the basis of criticism. Our report relied on direct in-water observations, conducted at peak densities over two spawning years. The critique ignores this, choosing instead to focus on a supplementary video which was not the basis of our conclusions. Like other researchers working on this species, we did not directly observe mating, but report courtship as a well-established proxy used across mating systems studies. Apart from these methodological concerns, the authors suggest that there is no theoretical support for our observations. However, sexual selection theory provides well-established frameworks showing that, at very high mating densities, a variety of tactics can emerge, that often vary considerably between populations and locations. In our original paper, we use this broader theory of sexual selection together with detailed behavioural data to propose plausible evolutionary explanations that bear testing in these novel, high-density systems. We agree with the authors that novel observations should be scrutinised carefully as they can challenge our current understanding of the range of behaviours populations display and serve as a springboard for theoretical advancement. Given their rarity, these observations should be evaluated against the rigour of their documentation and the transparency of their reporting. In this context, we hope our carefully documented observations serve as a useful addition to the fascinating and complex natural history of species like the squaretail grouper
Data from: Alternative reproductive tactics and inverse size-assortment in a high-density fish spawning aggregation
Background: At high densities, terrestrial and marine species often employ alternate reproductive tactics (ARTs) to maximize reproductive benefits. We describe ARTs in a high-density and unfished spawning aggregation of the squaretail grouper (Plectropomus areolatus) in Lakshadweep, India. Results: As previously reported for this species, territorial males engage in pair-courtship, which is associated with a pair-spawning tactic. Here, we document a previously unreported school-courtship tactic; where territorial males court multiple females in mid-water schools, which appears to culminate in a unique ‘school-spawning’ tactic. Courtship tactics were conditional on body size, local mate density and habitat, likely associated with changing trade-offs between potential mating opportunities and intra-sexual competition. Counter-intuitively, the aggregation showed a habitat-specific inverse size-assortment: large males courted small females on the reef slope while small males courted equal-sized or larger females on the shelf. These patterns remained stable across two years of observation at high, unfished densities. Conclusions: These unique density-dependent behaviours may disappear from this aggregation as overall densities decline due to increasing commercial fishing pressure, with potentially large consequences for demographics and fitness
Long-lived groupers require structurally stable reefs in the face of repeated climate change disturbances
14 páginas, 6 figuras, 5 tablas.Benthic recovery from climate-related disturbances
does not always warrant a commensurate functional
recovery for reef-associated fish communities. Here, we
examine the distribution of benthic groupers (family Serranidae)
in coral reef communities from the Lakshadweep
archipelago (Arabian Sea) in response to structural complexity
and long-term habitat stability. These coral reefs that
have been subject to two major El Nin˜o Southern Oscillation-
related coral bleaching events in the last decades (1998
and 2010). First, we employ a long-term (12-yr) benthicmonitoring
dataset to track habitat structural stability at
twelve reef sites in the archipelago. Structural stability of
reefs was strongly driven by exposure to monsoon storms
and depth, which made deeper and more sheltered reefs on
the eastern aspect more stable than the more exposed (western)
and shallower reefs. We surveyed groupers (species
richness, abundance, biomass) in 60 sites across the entire
archipelago, representing both exposures and depths. Sites
were selected along a gradient of structural complexity from
very low to high. Grouper biomass appeared to vary with
habitat stability with significant differences between depth
and exposure; sheltered deep reefs had a higher grouper
biomass than either sheltered shallow or exposed (deep and
shallow) reefs. Species richness and abundance showed
similar (though not significant) trends. More interestingly,
average grouper biomass increased exponentially with
structural complexity, but only at the sheltered deep (high
stability) sites, despite the availability of recovered structure
at exposed deep and shallow sites (lower-stability sites). This
trend was especially pronounced for long-lived groupers
(life span [10 yrs). These results suggest that long-lived
groupers may prefer temporally stable reefs, independent of
the local availability of habitat structure. In reefs subject to
repeated disturbances, the presence of structurally stable
reefs may be critical as refuges for functionally important,
long-lived species like groupers.Peer reviewe
male and female size distribution
File contains point count data taken in slope and shelf habitats at the aggregation site on the distribution of males and females of two size classes : small and large
male activity
Time-Activity (aggression, spawning interaction, rove and rest) of large and small males in the slope and shelf habitat