Spawning migrations in the monogamous butterflyfish,Chaetodon trifasciatus

Spawning and related behavior of a monogamous butterflyfish,Chaetodon trifasciatus, were observed at Kuroshima Island, Okinawa, Japan. Each heterosexual pair defended a feeding territory in the daytime. Spawning occurred at dusk on the days around full or new moon in the daytime. Spawning occurred at dusk on the days around full or new moon in the vicinity of offshore tidal currents. Spawning migration to such sites occurred in pairs, the feeding territories of which were located in areas of inshore currents. In the evening each pair established a small temporary territory, which they spawned adjacent to and slept within until the next morning. The distribution of sleeping sites as well as tidal current directions may determine the spawning sites of this butterflyfish.     

Fishes associated with artificial reefs: attributing changes to attraction or production using novel approaches

Two widely‐recognized hypotheses propose that increases in fish abundance at artificial reefs are caused by (a) the attraction and redistribution of existing individuals, with no net increase in overall abundance and (b) the addition of new individuals by production, leading to a net increase in overall abundance. Inappropriate experimental designs have prevented many studies from discriminating between the two processes. Eight of 11 experiments comparing fish abundances on artificial reefs with those on adjacent soft bottom habitats were compromised by a lack of replication or spatial interspersion in the design itself. Only three studies featured proper controls and replicated designs with the interspersion of reef and control sites. Goodness of fit tests of abundance data for 67 species from these studies indicated that more fishes occur on reefs than on controls, particularly for species that typically occur over hard substrata. Conversely, seagrass specialists favour controls over reefs. Changes in the appearance of fish abundance trajectories driven by manipulation of sampling intervals highlight the need for adequate temporal sampling to encompass key life history events, particularly juvenile settlement. To ultimately determine whether attraction and production is responsible for increased abundances on reefs, requires two experimental features: 1) control sites, both interspersed among artificial reefs and at reef and non‐reef locations outside the test area and 2) incorporation of fish age and length data over time. Techniques such as otolith microchemistry, telemetry and stable isotope analysis can be used to help resolve feeding and movement mechanisms driving attraction and production.     

Reefs of tomorrow: eutrophication reduces coral biodiversity in an urbanized seascape

Although the impacts of nutrient pollution on coral reefs are well known, surprisingly, no statistical relationships have ever been established between water quality parameters, coral biodiversity and coral cover. Hong Kong provides a unique opportunity to assess this relationship. Here, coastal waters have been monitored monthly since 1986, at 76 stations, providing a highly spatially resolved water quality dataset including 68 903 data points. Moreover, a robust coral species richness (S) dataset is available from more than 100 surveyed locations, composed of 3453 individual colonies' observations, as well as a coral cover (CC) dataset including 85 sites. This wealth of data provides a unique opportunity to test the hypothesis that water quality, and in particular nutrients, drives coral biodiversity. The influence of water quality on S and CC was analyzed using GIS and multiple regression modeling. Eutrophication (as chlorophyll‐a concentration; CHLA) was negatively correlated with S and CC, whereas physicochemical parameters (DO and salinity) had no significant effect. The modeling further illustrated that particulate suspended matter, dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP) had a negative effect on S and on CC; however, the effect of nutrients was 1.5‐fold to twofold greater. The highest S and CC occurred where CHLA <2 μg L^?1, DIN < 2 μm and DIP < 0.1 μm . Where these values were exceeded, S and CC were significantly lower and no live corals were observed where CHLA > 15 μg L^?1, DIN > 9 μm and DIP > 0.33 μm . This study demonstrates the importance of nutrients over other water quality parameters in coral biodiversity loss and highlights the key role of eutrophication in shaping coastal coral reef ecosystems. This work also provides ecological thresholds that may be useful for water quality guidelines and nutrient mitigation policies.     

Modelling marine community responses to climate‐driven species redistribution to guide monitoring and adaptive ecosystem‐based management

As a consequence of global climate‐driven changes, marine ecosystems are experiencing polewards redistributions of species – or range shifts – across taxa and throughout latitudes worldwide. Research on these range shifts largely focuses on understanding and predicting changes in the distribution of individual species. The ecological effects of marine range shifts on ecosystem structure and functioning, as well as human coastal communities, can be large, yet remain difficult to anticipate and manage. Here, we use qualitative modelling of system feedback to understand the cumulative impacts of multiple species shifts in south‐eastern Australia, a global hotspot for ocean warming. We identify range‐shifting species that can induce trophic cascades and affect ecosystem dynamics and productivity, and evaluate the potential effectiveness of alternative management interventions to mitigate these impacts. Our results suggest that the negative ecological impacts of multiple simultaneous range shifts generally add up. Thus, implementing whole‐of‐ecosystem management strategies and regular monitoring of range‐shifting species of ecological concern are necessary to effectively intervene against undesirable consequences of marine range shifts at the regional scale. Our study illustrates how modelling system feedback with only limited qualitative information about ecosystem structure and range‐shifting species can predict ecological consequences of multiple co‐occurring range shifts, guide ecosystem‐based adaptation to climate change and help prioritise future research and monitoring.     

Hogfish Lachnolaimus maximus (Labridae) confirmed in the south‐western Atlantic Ocean

Based on material deposited in collections, photographic records and other reports from fishermen and divers, the occurrence of the hogfish Lachnolaimus maximus (Labridae) is confirmed in the south‐western Atlantic Ocean, near the Brazilian coast as far south as southern Brazil. The recognized range of this species should therefore be extended c. 3000 km further south.     

Depth‐dependent plasticity in opsin gene expression varies between damselfish (Pomacentridae) species

Phenotypic plasticity plays an important role in adapting the visual capability of many animal species to changing sensory requirements. Such variability may be driven by developmental change or may result from environmental changes in light habitat, thereby improving performance in different photic environments. In this study, we examined inter‐ and intraspecific plasticity of visual sensitivities in seven damselfish species, part of the species‐rich and colourful fish fauna of the Great Barrier Reef in Australia. Our goal was to test whether the visual systems of damselfish were tuned to the prevailing light environment in different habitats and/or other aspects of their lifestyle. More specifically, we compared the opsin gene expression levels from individuals living in different photic habitats. We found that all species expressed rod opsin (RH1) used for dim‐light vision, and primarily three cone opsins (SWS1, RH2B and RH2A) used for colour vision. While RH1 levels changed exclusively following a diurnal cycle, cone opsin expression varied with depth in four of the seven species. Estimates of visual pigment performance imply that changes in opsin expression adjust visual sensitivities to the dominant photic regime. However, we also discovered that some species show a more stable opsin expression profile. Further, we found indication that seasonal changes, possibly linked to changes in the photic environment, might also trigger opsin expression. These findings suggest that plasticity in opsin gene expression of damselfish is highly species‐specific, possibly due to ecological differences in visual tasks or, alternatively, under phylogenetic constraints.     

Congruent patterns of connectivity can inform management for broadcast spawning corals on the Great Barrier Reef

Connectivity underpins the persistence and recovery of marine ecosystems. The Great Barrier Reef (GBR) is the world's largest coral reef ecosystem and managed by an extensive network of no‐take zones; however, information about connectivity was not available to optimize the network's configuration. We use multivariate analyses, Bayesian clustering algorithms and assignment tests of the largest population genetic data set for any organism on the GBR to date (Acropora tenuis, >2500 colonies; >50 reefs, genotyped for ten microsatellite loci) to demonstrate highly congruent patterns of connectivity between this common broadcast spawning reef‐building coral and its congener Acropora millepora (~950 colonies; 20 reefs, genotyped for 12 microsatellite loci). For both species, there is a genetic divide at around 19°S latitude, most probably reflecting allopatric differentiation during the Pleistocene. GBR reefs north of 19°S are essentially panmictic whereas southern reefs are genetically distinct with higher levels of genetic diversity and population structure, most notably genetic subdivision between inshore and offshore reefs south of 19°S. These broadly congruent patterns of higher genetic diversities found on southern GBR reefs most likely represent the accumulation of alleles via the southward flowing East Australia Current. In addition, signatures of genetic admixture between the Coral Sea and outer‐shelf reefs in the northern, central and southern GBR provide evidence of recent gene flow. Our connectivity results are consistent with predictions from recently published larval dispersal models for broadcast spawning corals on the GBR, thereby providing robust connectivity information about the dominant reef‐building genus Acropora for coral reef managers.     

Marine reserves indirectly affect fine‐scale habitat associations,but not overall densities,of small benthic fishes

Many large, fishery‐targeted predatory species have attained very high relative densities as a direct result of protection by no‐take marine reserves. Indirect effects, via interactions with targeted species, may also occur for species that are not themselves targeted by fishing. In some temperate rocky reef ecosystems, indirect effects have caused profound changes in community structure, notably the restoration of predator–urchin–macroalgae trophic cascades. Yet, indirect effects on small benthic reef fishes remain poorly understood, perhaps because of behavioral associations with complex, refuge‐providing habitats. Few, if any, studies have evaluated any potential effects of marine reserves on habitat associations in small benthic fishes. We surveyed densities of small benthic fishes, including some endemic species of triplefin (Tripterygiidae), along with fine‐scale habitat features in kelp forests on rocky reefs in and around multiple marine reserves in northern New Zealand over 3 years. Bayesian generalized linear mixed models were used to evaluate evidence for (1) main effects of marine reserve protection, (2) associations with habitat gradients, including complexity, and (3) differences in habitat associations inside versus outside reserves. No evidence of overall main effects of marine reserves on species richness or densities of fishes was found. Both richness and densities showed strong associations with gradients in habitat features, particularly habitat complexity. In addition, some species exhibited reserve‐by‐habitat interactions, having different associations with habitat gradients inside versus outside marine reserves. Two species (Ruanoho whero and Forsterygion flavonigrum) showed stronger positive associations with habitat complexity inside reserves. These results are consistent with the presence of a behavioral risk effect, whereby prey fishes are more strongly attracted to habitats that provide refuge from predation in areas where predators are more abundant. This work highlights the importance of habitat structure and the potential for fishing to affect behavioral interactions and the interspecific dynamic attributes of community structure beyond simple predator–prey consumption and archetypal trophic cascades.