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It has become almost paradigmatic in the coral reef literature that fishing-induced reductions of parrotfish abundance cause benthic phase shifts from coral to macroalgal dominance. This study examined the alternatives of top-down control of the benthos by parrotfish density and bottom-up control of parrotfish density by the benthos at four Philippine islands in a long-term (7.5-30 years) 'natural experiment'. No-take marine reserves (NTMRs) demonstrated that fishing reduced parrotfish density significantly at two islands (Sumilon, Mantigue), but not significantly at two other islands (Apo, Selinog). There was no evidence that cover of hard coral decreased, nor macroalgal cover increased, in fished areas relative to NTMRs, no evidence that parrotfish density affected hard coral cover significantly, and thus no evidence of top-down, fishing-induced benthic phase shifts at all four islands. There was, however, compelling evidence that benthos (cover of dead substrata and hard coral) exerted strong bottom-up control on parrotfish density. This bottom-up control was demonstrated most clearly by major environmental disturbances (e.g. typhoons, coral bleaching) that changed benthic habitat and, subsequently, parrotfish density. As hard coral cover declined (and cover of dead substratum increased), parrotfish density increased and vice versa. This response occurred in both major parrotfish feeding guilds (scrapers and excavators). This long-term study on heavily fished coral reefs suggests that the benthos drives the parrotfish, not the other way around. The paradigm of fishing-induced benthic phase shifts may not apply to all coral reefs at all times. Multiple drivers of benthic change on coral reefs should always be considered. Electronic supplementary material The online version of this article (doi:10.1007/s00227-015-2728-3) contains supplementary material, which is available to authorized users., Author(s): Garry R. Russ[sup.1] [sup.2] , Sarah-Lee A. Questel[sup.1] [sup.2] , Justin R. Rizzari[sup.1] [sup.2] , Angel C. Alcala[sup.3] Author Affiliations: (1) College of Marine and Environmental Sciences, James Cook [...]

Quantifying the distribution and habitat use of sharks is critical for understanding their ecological role and for establishing appropriate conservation and management regimes. On coral reefs, particularly the Great Barrier Reef (GBR), little is known regarding the distribution of sharks across major reef habitat types. In this study, we surveyed shark populations across outer-shelf reefs of the GBR in order to determine the diversity, abundance, and distribution of reef sharks across three major coral reef habitats: (1) the reef slope, (2) the back reef and (3) the reef flat. Model selection revealed that habitat was the principal factor influencing shark distribution and abundance. Specifically, overall shark abundance and diversity were significantly higher on the reef slope (and to a lesser degree, the back reef) than the reef flat. This confirms that shark populations are not homogeneously distributed across coral reefs. Thus, the results presented herein have important implications for shark population assessments. In addition, our results highlight the potential importance of the reef slope, with high levels of live coral cover and structural complexity, for sustaining reef shark populations. As this habitat is highly susceptible to disturbance events, this study provides a useful context for predicting and understanding how environmental degradation may influence reef shark populations in the future., Introduction Basic knowledge of habitat use is essential in clarifying the ecological role of a particular species, and for improving site-based protection approaches for species that are susceptible to overfishing [...]

Simple Summary: In eastern Australia, the movement of subadult and adult white sharks is poorly understood as very few animals are encountered. To investigate how deep they dive, where they travel and water temperatures they live in, we tagged three white sharks (340–388 cm total length) between May 2021 and January 2022. All sharks moved away from the coast after release and preferred offshore habitats. The three sharks mainly stayed within 50 m of the surface, in water temperatures between 14–19 °C and dived deeper during the day. They all moved north–south along the coastline and spent little time in the same location but there was evidence that they stayed in some locations longer than others. Very little information is available for adult white sharks in eastern Australia and studies like this provide key information about their preferences. As they travel long distances it is important for multijurisdictional management to effectively mitigate human-shark interactions whilst supporting conservation efforts. In eastern Australia, white sharks (Carcharodon carcharias) are targeted in shark control programs, yet the movement of subadults and adults of the eastern Australasian population is poorly understood. To investigate horizontal and vertical movement and habitat use in this region, MiniPAT pop-up satellite archival tags were deployed on three larger white sharks (340–388 cm total length) between May 2021 and January 2022. All sharks moved away from the coast after release and displayed a preference for offshore habitats. The upper < 50 m of the water column and temperatures between 14–19 °C were favoured, with a diel pattern of vertical habitat use evident as deeper depths were occupied during the day and shallower depths at night. Horizontal movement consisted of north–south seasonality interspersed with periods of residency. Very little information is available for adult white sharks in eastern Australia and studies like this provide key baseline information for their life history. Importantly, the latitudinal range achieved by white sharks illuminate the necessity for multijurisdictional management to effectively mitigate human-shark interactions whilst supporting conservation efforts of the species. [ABSTRACT FROM AUTHOR]

A 6‐week laboratory experiment exposed juvenile Ambon damselfish Pomacentrus amboinensis to visual and chemical cues of either a predator, a herbivore or a null control (sea water) and found no effect of predator cues on prey morphology (proportion of ocellus to eye diameter, body depth, standard length and fin area). Nonetheless, behaviour was significantly affected by predator presence, with prey less active and taking half as many feeding strikes when exposed to predators compared to fish from the null control. The presence of a herbivore also affected prey behaviour similar to that of the predator, suggesting that the presence of a non‐predator may have important effects on development. [ABSTRACT FROM AUTHOR]

Bleaching (whitening) of cnidarians such as corals and sea anemones has caused widespread degradation of coral reefs around the world and is therefore an urgent issue for coral reef science and conservation. Although cnidarians often bleach in aquaria, methods for experimental induction of bleaching in wild cnidarians are lacking, which impedes scientists' ability to understand the ultimate effects of bleaching on the broader ecosystem. In this study, we investigated the utility of an in situ method for experimental induction of bleaching in the tropical sea anemone Heteractis crispa. Healthy, wild anemones were covered with opaque black plastic sheets, mesh cages or left undisturbed (controls) and tentacle colour and body size were monitored with a colour reference card and flexible tape, respectively, every 1-3 days for 15 days. Caged and control anemones remained unchanged for the duration of the experiment, but covered anemones commenced whitening after 4-6 days and were completely white after 7-14 days (mean time to bleaching ± SE = 10.1 ± 0.7 days). Experimental bleaching occurred without reduction in anemone body size and was visibly similar to natural bleaching seen previously in H. crispa. We hypothesize that light-deprivation, reduced water flow, physical contact or some combination of these factors caused the bleaching. This study provides the basis for a simple and rapid method of inducing bleaching in situ, which releases scientists' dependence on sporadic natural bleaching events or artificial aquarium experiments, and provides a means to investigate the effects of bleaching on other ecosystem components such as fishes. [ABSTRACT FROM AUTHOR]