Temperate Reef Fish Research Articles

A Comparison of Methods of Visual Census and Cryptobenthic Fish Collecting, an Integrative Approach to the Qualitative and Quantitative Composition of the Mediterranean Temperate Reef Fish Assemblages

The present research quantitatively compared the fish composition among two methods for non-cryptic benthic fish species and one method for cryptobenthic fish species for the first time for the Mediterranean temperate reef fish assemblage. A visual census of fishes was performed within a cylinder of 4 m radius and within a cylinder of 2 m radius, while the cryptobenthic fishes were collected using a square of 1 m2 with anesthetic. The data and material were collected at fifty sampling points. The visual census methods together recorded 31 species, and the square with anesthetic method recorded 18 species. The quantitative comparison of methods of visual census and cryptobenthic fish collecting showed significantly different species richness, total fish abundance, and fish assemblage structure among methods. The applied methods were highly complementary. The cylinder of 2 m radius is well suited for epibenthic fishes and the cylinder of 4 m radius is reliable for hyperbenthic and benthopelagic fishes. Therefore, each of the methods well covered one of three components of ichthyobenthos (hyperbenthic, epibenthic, and cryptobenthic fishes), and all three methods together provided a far more complete assessment of fish species composition than any individual census method for the Mediterranean littoral benthic fishes.

A data-driven approach to multiple-stressor impact assessment for a marine protected area.

The coastal environment is not managed in a way that considers the impact of cumulative threats, despite being subject to threats from all realms (marine, land, and atmosphere). Relationships between threats and species are often nonlinear; thus, current (linear) approaches to estimating the impact of threats may be misleading. We developed a data-driven approach to assessing cumulative impacts on ecosystems and applied it to explore nonlinear relationships between threats and a temperate reef fish community. We used data on water quality, commercial fishing, climate change, and indicators of recreational fishing and urbanization to build a cumulative threat map of the northern region in New South Wales, Australia. We used statistical models of fish abundance to quantify associations among threats and biophysical covariates and predicted where cumulative impacts are likely to have the greatest impact on fish. We also assessed the performance of no-take zones (NTZs), to protect fish from cumulative threats across 2 marine protected area networks (marine parks). Fishing had a greater impact on fish than water quality threats (i.e., percent increase above the mean for invertivores was 337% when fishing was removed and was 11% above the mean when water quality was removed inside NTZs), and fishing outside NTZs affected fish abundances inside NTZs. Quantifying the spatial influence of multiple threats enables managers to understand the multitude of management actions required to address threats.

Whole-genome sequencing reveals fine-scale environment-associated divergence near the range limits of a temperate reef fish.

Environmental variation is increasingly recognized as an important driver of diversity in marine species despite the lack of physical barriers to dispersal and the presence of pelagic stages in many taxa. A robust understanding of the genomic and ecological processes involved in structuring populations is lacking for most marine species, often hindering management and conservation action. Cunner (Tautogolabrus adspersus) is a temperate reef fish with both pelagic early life-history stages and strong site-associated homing as adults; the species is also of interest for use as a cleaner fish in salmonid aquaculture in Atlantic Canada. We aimed to characterize genomic and geographic differentiation of cunner in the Northwest Atlantic. To achieve this, a chromosome-level genome assembly for cunner was produced and used to characterize spatial population structure throughout Atlantic Canada using whole-genome sequencing. The genome assembly spanned 0.72 Gbp and 24 chromosomes; whole-genome sequencing of 803 individuals from 20 locations from Newfoundland to New Jersey identified approximately 11 million genetic variants. Principal component analysis revealed four regional Atlantic Canadian groups. Pairwise FST and selection scans revealed signals of differentiation and selection at discrete genomic regions, including adjacent peaks on chromosome 10 across multiple pairwise comparisons (i.e. FST 0.5-0.75). Redundancy analysis suggested association of environmental variables related to benthic temperature and oxygen range with genomic structure. Results suggest regional scale diversity in this temperate reef fish and can directly inform the collection and translocation of cunner for aquaculture applications and the conservation of wild populations throughout the Northwest Atlantic.

Oyster aquaculture cages provide fish habitat similar to natural structure with minimal differences based on farm location

Oyster aquaculture gear may augment natural seafloor by providing structured habitat for economically important fish species. Underwater video census was used to assess fish abundance and community composition on eastern oyster (Crassostrea virginica) shelf and bag style aquaculture off-bottom cages and within natural rock reef habitat. During 2018, underwater cameras were mounted on four study cages at a dense shellfish farm of 40-100 commercial cages (dense cage farm), on four single cages interspersed on low relief seafloor (sparse cage farm), and amongst four boulders on a rock reef (rock reef), within an embayment off Milford, Connecticut, which is part of Long Island Sound, in the United States. In 2019, cameras were similarly deployed on two study cages per farm at each of three shellfish farms off Milford, Norwalk and Westport, CT. Video was recorded hourly in eight-minute segments from 7 am to 7 pm. Data loggers monitored seawater temperature, light intensity, and current speed. Fish abundance (MaxN) was calculated for all videos. We compared fish abundance and community composition between May and September, on cage and boulder habitat, on cages at dense and sparse farms and on cages across farm locations. In 2018, abundance of black sea bass (Centropristis striata), scup (Stenotomus chrysops) and tautog (Tautoga onitis) was significantly higher on cages than boulders, regardless of cage number. Cunner (Tautogolabrus adspersus) abundance was significantly higher on boulders than cages when cage sites were grouped. However pairwise comparisons indicated that cunner were significantly higher at the sparse cage farm versus the rock reef but cunner abundance on the dense cage farm and rock reef sites was not significantly different. Abundance of black sea bass, scup, tautog, and cunner were not significantly different across 2019 farm locations. Young-of-the-year fish occurred episodically at all sites during both years, with black sea bass and scup most abundant. Fish abundance corresponded to seasonal changes in seawater temperature and was highest at the warmest temperatures. Light intensity and current speed explained less variation in fish abundance relative to temperature, and relationships were inconsistent across habitats and farm locations Our results suggest that multi-tiered oyster aquaculture cages contribute structure to seafloor environments that provide habitat for temperate reef fish similar to natural rock reefs.

Reference Genome of the Black Surfperch, Embiotoca jacksoni (Embiotocidae, Perciformes), a California Kelp Forest Fish That Lacks a Pelagic Larval Stage.

Surfperches (Family Embiotocidae) are viviparous temperate reef fishes that brood their young. This life history trait translates into limited dispersal, strong population structure, and an unusually strong potential for local adaptation in a marine fish. As part of the California Conservation Genomics Project (CCGP), we sequenced the genome of the Black Surfperch, Embiotoca jacksoni, to establish a genomic model for understanding phylogeographic patterns of marine organisms in California. These patterns, in turn, may inform the design of marine protected areas using dispersal models based on genomic data. The genome of E. jacksoni is typical of marine fishes at less than 1Gb (genome size = 635 Mb), and our assembly is near-chromosome level (contig N50 = 6.5Mb, scaffold N50 = 15.5 Mb, BUSCO = 98.1%). Within the context of the CCGP, the genome will be used as a reference for future whole genome resequencing projects aimed at enhancing our knowledge of the population structure of the species, and efficacy of Marine Protected Areas across the state.

Impacts of an invasive alga on recruitment of a temperate reef fish

The invasive brown macroalga, Sargassum horneri (devil weed), has spread along the southern California coast, replacing the native habitat-forming macroalga, Macrocystis pyifera (giant kelp). M. pyrifera is a critical habitat for macroalgal-associated fishes, especially for the arrival and survival of juvenile fish that constitutes recruitment success. It is unclear whether critical processes in recruitment may be altered if S. horneri replaces M. pyrifera as the dominant biogenic macroalgal habitat on rocky reefs. Through a series of laboratory experiments, we investigated the effects of macroalgal identity on post-settlement processes contributing to recruitment success for a common macrophyte-associated fish, Heterostichus rostratus (giant kelpfish). To evaluate the potential impacts of S. horneri vs. M. pyrifera in their effects on juvenile H. rostratus, we explored whether there were differences for H. rostratus in their (1) habitat choice in the presence of both macroalgae, (2) prey choice employing the mysid shrimp, Holmesimysis costata, that were fed on either of the two macroalgae, and (3) predator-mediated mortality by Paralabrax clathratus (kelp bass), a common piscivore in both macroalgal habitats. The results of these experiments suggest that for the post-settlement processes evaluated here, macroalgal identity does not appear to have a significant impact on giant kelpfish, and recruitment success in S. horneri habitat may be equivalent to that observed in M. pyrifera. It is possible, however, that differential settlement to these macroalgae, species-specific habitat requirements, or other post-settlement factors may play a role in influencing recruitment success within each of these two habitats. Conducting further studies that include ambient invertebrate prey densities of H. rostratus in each macroalgal habitat, particularly in a field setting, will potentially provide greater insight into these processes.

Reef Fish Diversity Across the Temperate South Pacific Ocean

Patterns of species richness and their structuring forces at multiple scales provide a critical context for research efforts focusing on ecology, evolution, and conservation. Diversity gradients have been demonstrated in tropical reef fish, but corresponding patterns and mechanisms remain poorly understood in temperate regions. We conducted hierarchical (spatially nested) sampling of temperate reef fish faunas across > 140 degrees of longitude in the eastern and western South Pacific Ocean. Our sampling efforts spanned five distinct provinces: the Southeast Australian Shelf (SAS), Northern and Southern New Zealand (N-SNZ), Juan Fernandez and Desventuradas Islands (JFD), and the Warm Temperate Southeastern Pacific (WTPA). We evaluated (i) spatial variation in patterns of species richness and abundance (using Chao 1 index), and distribution of functional diversity (using several functional attributes: max body size, trophic groups, feeding guilds, trophic level, habitat use, gregariousness, and activity patterns) and (ii) scale-dependencies in these patterns. Species richness declined from west to east across the temperate South Pacific, but this pattern was detectable only across larger spatial scales. A functional redundancy index was significantly higher in the western South Australian Shelf at multiple scales, revealing that species contribute in equivalent ways to an ecosystem function such that one species may substitute for another. We also detected that patterns of variation in functional diversity differed from patterns of variation in species richness, and were also dependent on the spatial scale of analysis. Lastly, we identified that species’ traits are not equally distributed among reef fish assemblages, where some provinces are characterized by a distinct functional component within their reef fish assemblages. Planktivorous and schooling species, for instance, dominated the assemblages in the eastern Pacific, which is characterized by higher primary productivity and steep bathymetric slopes favoring these traits. Demersal and pairing behavior traits dominated the reef fish assemblages in western Pacific provinces (SAS, SNZ). We conclude that combining the identifies and species’ traits allow us to disentangle historical, biogeographic and environmental factors that structure reef fish fauna.

Tropicalization of temperate reef fish communities facilitated by urchin grazing and diversity of thermal affinities

AbstractAimGlobal declines in structurally complex habitats are reshaping both land‐ and seascapes in directions that affect the responses of biological communities to warming. Here, we test whether widespread loss of kelp habitats through sea urchin overgrazing systematically changes the sensitivity of fish communities to warming.LocationGlobal temperate latitudes.Time periodModern.Major taxa studiedFishes.MethodsCommunity shifts in thermal affinity related to habitat were assessed by simulating and comparing fish communities from 2271 surveys across 15 ecoregions.ResultsWe found that fishes in kelp and urchin barrens differed in realized thermal affinities and range sizes, but only in regions where species pools had high variability in the thermal affinities of species. Barrens on warm temperate reefs host relatively more warm‐affinity fish species than neighbouring kelp beds, highlighting the acceleration of tropicalization processes facilitated by urchin grazing. In contrast, proportionally more cool‐affinity fishes colonize barrens at high temperate latitudes, contributing to community lags with ocean warming in these regions.Main conclusionsOur findings implicate urchins as drivers of ecological change, in part by affecting ecological resilience to warming.

Mismatch between shape changes, early growth, and condition for a temperate reef fish from an oceanic island

Settlement is a key process in the life history of marine fish, when shape and ecological changes occur during the transition from a pelagic larva to a benthic juvenile. We studied the covariation of shape changes, condition, and pre- and post-settlement growth of settlers (17–30 mm) of the wrasse, Pseudolabrus gayi, from the Robinson Crusoe island, south-eastern Pacific. Specimens were collected during late March 2018 from four locations at 20 m depth and from a large, natural intertidal pool. The morphospace and the allometry were characterised by landmark-based geometric morphometrics, size and growth were estimated using sagittae otolith microstructure analysis, and condition was determined using the Fulton index. The settler’s phenotype varied from a robust shape with ventrally oriented mouth opening, to slender specimens with frontally oriented mouth, with similar body morphospace among sites. The mean pelagic larval duration was 44.8 ± 4.6 days, settling at 19 ± 2 mm SL. The mean post-settlement growth rate was low (0.09 mm day−1), showing low static allometry (3%). Differences among locations occurred in terms of settler’s condition and growth prior and after settlement, suggesting effects of the microhabitat and potential predators. Therefore, the variability in the settler’s morphospace was decoupled of pre- and post-settlement growth and condition during the transition from pelagic to benthic habitat. Finally, this study highlights the dynamic nature of the settlement–transition period for a temperate reef fish in a period when phenotype variations in body shape and early life-history traits vary asynchronously.

Environmentally induced morphological variation in the temperate reef fish, Forsterygion lapillum (F. Tripterygiidae)

Environmentally induced morphological variation in the temperate reef fish, Forsterygion lapillum (F. Tripterygiidae)

The influence of habitat association on swimming performance in marine teleost fish larvae

AbstractLatitude and body size are generally considered key drivers of swimming performance for larval marine fishes, but evidence suggests that evolutionary relationships and habitat may also be important. We used a comparative phylogenetic framework, data synthesis and case study approach to investigate how swimming performance differs among larvae of fish species across latitude. First, we investigated how swimming performance changed with body length, and we found that temperate reef fishes have the greatest increases in swimming performance with length. Secondly, we compared differences in three swimming performance metrics (critical swimming speed, in situ swimming, and endurance) among post‐flexion larvae, whilst considering phylogenetic relationships and morphology, and we found that reef fishes have higher swimming capacity than non‐reef (pelagic and non‐reef demersal) fishes, which is likely due to larger, more robust body sizes. Thirdly, we compared swimming performance of late‐stage larvae of tropical fishes with oceanographic data to better understand the ecological relevance of their high‐capacity swimming. We found that reef fishes have high swimming performance and grow larger than non‐reef fish larvae, which we suggest is due to the pressures to find a specific, patchily distributed habitat upon which to settle. Given the current bias towards studies on percomorph fishes at low latitudes, we highlight that there is a need for more research on temperate reef fish larvae and other percomorph lineages from high latitudes. Overall, our findings provide valuable context to understand how swimming and morphological traits that are important for dispersal and recruitment processes are selected for among teleost fish larvae.

Comparative thermal performance among four young-of-the-year temperate reef fish species

Abstract Identifying the role of temperature on species-specific performance is critical for predicting how species will respond to temperature increases expected under climate change. We compared the thermal performance of two sympatric Pacific rockfish species complexes (controls for relatedness and geographic location) that vary in larval life-history traits associated with different oceanographic regimes including temperature during early life-history stages: the BY complex (Black: Sebastes melanops, Yellowtail: S. flavidus) and the CQ complex (Copper: S. caurinus, Quillback: S. maliger). By using controlled experiments, we evaluated foraging activity, growth, and survival of young-of-the-year rockfish recruits under current and future habitat temperatures over a 14-day time period indicative of marine heatwave events expected with climate change. BY rockfish displayed a heat-intolerant behaviour by only foraging at temperatures within current habitat temperatures, whereas the CQ rockfish displayed a heat-tolerant behaviour by actively foraging at temperatures above current and future predicted temperatures for a limited time. Although growth and survival in each species significantly declined with temperature, the magnitude of the effect did not vary between species. Taken together, our results show that rockfish are capable of using different behavioural strategies to cope with warming and may be differentially impacted by future climate conditions.

Ontogenetic shifts in social aggregation and habitat use in a temperate reef fish

AbstractCover, both from physical structure or association with social groups, can reduce predation risk and increase foraging, leading to enhanced growth and survival, and is therefore a critical aspect of the niche for many organisms. However, the need for cover, or the need for a specific type of cover, may change as an individual grows in size, leading to niche shifts throughout development to meet these changing needs. In this study, we examine ontogenetic shifts in cover use by wild populations of a temperate reef fish, the southern hulafish, Trachinops caudimaculatus, a small, abundant planktivorous social aggregator found on temperate reefs in southern Australia. Through repeated in situ surveys, we found clear evidence of ontogenetic shifts in both microhabitat use and aggregation patterns by T. caudimaculatus juveniles in the first three months on the reef. The microhabitat associations of juvenile T. caudimaculatus became more similar to those of adult conspecifics over the study period, and over the same time frame, juveniles increasingly aggregated with adult shoals. Our findings also suggest that trade‐offs between structural and social cover are context‐dependent, with juveniles relying on structural cover longer when adult conspecific density (and thus intra‐specific competition) and/or habitat complexity (and thus the availability of shelter) is high. These findings provide rare and important observations into the complex interplay of social aggregations, habitat use, and ontogeny in wild fish populations.

Maternal age, length, and weight influence larval characteristics and viability in the viviparous temperate reef fish Helicolenus percoides

Mature age structure has been recognized as an important determinant of fecundity in fish populations. More recently it has been demonstrated that in some species, older, larger females can produce faster-growing and more viable larvae than younger, smaller females. We investigated this effect in sea perch Helicolenus percoides and collected information on fecundity as well as notochord length and oil globule volume (OGV) of larvae on the day of parturition, time to 50% mortality, and rate of change in length and OGV of cohorts of larvae in fed and unfed treatments. Absolute fecundity increased proportionally with maternal age and total length. Older, larger females produced cohorts of larvae with larger OGVs. These cohorts also had faster positive rates of change in length in the fed treatment than did cohorts of larvae produced by younger, smaller females. The OGV was positively correlated with rates of change in length and survival in the fed treatment; however, we did not detect influences on growth or survival in the unfed treatment. Further, cohorts of larvae in the unfed treatment had negative rates of change in length and lower survival compared to cohorts in the fed treatment. The results indicated that the OGV, which was affected by maternal age and size, was an important factor influencing larval growth and viability when external energy sources were available. These data provide insight into the reproductive biology of sea perch and highlight the importance of an old-growth age structure for effective larval viability and growth.

Local adaptation of antipredator behaviors in populations of a temperate reef fish.

The temperament of animals can vary among individuals and among populations, but it is often unclear whether spatial variation in temperament is the result of acclimation to local environmental conditions or genetic adaptation to spatial differences in natural selection. This study tested whether populations of a marine fish that experience different levels of mortality and fishing exhibited local adaptation in behaviors related to predator avoidance and evasion. First, we measured variation in reactivity to perceived risk in wild populations of black surfperch (Embiotoca jacksoni). We compared flight initiation distances (FID) between populations with significantly different mortality rates. After finding that FID values were substantially lower in the low-risk locations, we tested for local adaptation by rearing lab-born offspring from both high- and low-risk populations in a common environment before measuring their behavior. Lab-reared offspring from high- and low-risk populations exhibited significant differences in several behaviors related to reactivity. Between 23 and 43% of the total variation in behaviors we measured could be attributed to source population. These results thus suggest that a substantial amount of spatial variation in behaviors related to predator evasion may represent local adaptation. In addition, behaviors we measured had an average, broad-sense heritability of 0.24, suggesting that the behavioral tendencies of these populations have some capacity to evolve further in response to any changes in selection.

Size and stage-dependent vertical migration patterns in reef-associated fish larvae off the eastern coast of Australia

Larval fish have been shown to vertically migrate with ontogeny, a behaviour that influences their dispersal by exposing the larvae to currents with different velocities at different stages of development. Most studies have focused on studying the vertical migration of tropical reef fishes, that have been shown in general to migrate downwards with ontogeny. Here we investigated if similar ontogenetic vertical migration patterns also occur for seven families of temperate reef fish along the eastern coast of Australia, sampling at three depth ranges (0–1 m, 5–50 m, 51–100 m) across sixteen stations along the continental shelf, and eight within cold-core eddies. Larval fish were identified to the lowest taxonomic level possible, their standard length measured, and ontogenetic stage classified to preflexion, flexion or postflexion. Generalised linear models were used to determine if the larval fish exhibited patterns of vertical migration with ontogeny and length. Four families (Labridae, Serranidae, Scorpaenidae, and Synodontidae) exhibited a downwards migration with ontogeny similar to vertical distribution patterns seen in tropical reef fish studies, Mullidae displayed different vertical migration patterns within eddies compared to coastal waters, and two families showed no ontogenetic vertical migration (Pomacentridae and Scaridae). For all families other than Scaridae, the larvae inside an eddy were longer suggesting larval retention. The vertical migration patterns observed, while varying among taxa, show that reef-associated larval fish off the eastern Australian coast do change their depth with ontogeny. The results of this study will be useful in parameterising connectivity modelling studies for these temperate reef-associated families.

Chemical cues from habitats and conspecifics guide sand-smelt Atherina presbyter larvae to reefs

Chemical cues have been widely addressed as potential cues for fish larvae to orient, detect or remain close to suitable habitat. However, most studies to date have been on tropical reef species and have suggested a chemosensory-driven homing behaviour, with only few studies on temperate fish indicating a less conclusive response to chemical cues. We hypothesized that detection and response to chemical cues might provide an important mechanism maintaining the larvae of a temperate reef fish species (sand-smelt Atherina presbyter Cuvier, 1829), close to their natal reef. The ability to discriminate chemical cues from different rocky reefs, and natal and non-natal conspecifics was tested. Water and shoals of sand-smelt larvae were collected from 3 reefs, and larval preference was tested in a 2-choice flume chamber. Larvae preferred nearby reefs over natal reefs and discriminated and preferred conspecifics from their natal reef. Moreover, our results suggested that both cues are equally relevant, as the combination of reef cues with conspecifics was more attractive to sand-smelt than either cue in isolation. When conspecific and reef preferences were tested against each other, there was no longer a clear preference for either cue. Additional tests suggested that preference for conspecifics could be driven by either diet or habitat-related chemical cues. Chemical cues and the corresponding detection mechanisms likely play an important role in finding suitable habitat and increasing the fitness of temperate reef fish.

Fishing in hot waters threatens phenotypic diversity.

In Focus: Morrongiello, J. R., Sweetman, P. C., & Thresher, R. E. (2019). Fishing constrains phenotypic responses of marine fish to climate variability. Journal of Animal Ecology, 88, 1645-1656. Forces of unnatural selection, such as climate change and harvest, are rarely studied in concert, yet hold thegreat potential to act synergistically on individual performance, susceptibility to harvest, tolerance to warming temperatures, and ultimately population persistence and resilience. In this paper, Morrongiello etal. (2019) used long-term monitoring of a site-attached temperate reef fish, the purple wrasse (Notolabrus fucicola), to test novel predictions about how fisheries management and climate variability could alter individual growth rates and thermal reaction norms within and across stocks. Otolith growth increments were collected from three south-east Australian populations between 1980 and 1999, pre- and post-harvest, throughout an intensive warming spell. Using hierarchical models to partition variation in growth within and between individuals and populations, Morrongiello etal. detected increased average growth rate with warming, a release from density dependence post-harvest, and a fishing-by-warming interaction that decreased diversity in thermal growth reaction norms because large individuals that tend to better tolerate warm temperatures were effectively culled from the population. This study outlines the importance of determining which phenotypes are more resilient to increasing temperatures, how fisheries should manage for them, and how such collective knowledge could help preserve and even promote resilience of managed populations to increasing temperatures in ecosystems threatened by climate change.

Expanded consumer niche widths may signal an early response to spatial protection.

Marine management interventions are increasingly being implemented with the explicit goal of rebuilding ocean ecosystems, but early responses may begin with alterations in ecological interactions preceding detectable changes in population-level characteristics. To establish a baseline from which to monitor the effects of spatial protection on reef fish trophic ecology and track future ecosystem-level changes, we quantified temperate reef fish densities, size, biomass, diets and isotopic signatures at nine sites nested within two fished and one five-year old marine protected area (MPA) on the northwest coast of Canada. We calculated rockfish (Sebastes spp.) community and species-specific niche breadth for fished and protected areas based on δ13C and δ15N values. We found that rockfish community niche width was greater inside the MPA relative to adjacent fished reefs due to an expanded nitrogen range, possibly reflecting early changes in trophic interactions following five years of spatial protection. Our data also demonstrated that the MPA had a positive effect on the δ15N signature of rockfish (i.e., trophic position), but the effect of rockfish length on its own was not well-supported. In addition, we found a positive interaction between rockfish length and δ15N signature, such that δ15N signatures of rockfish caught within the MPA increased more rapidly with body size than those caught in fished areas. Differences in rockfish size structure and biomass among fished and unfished areas were not clearly evident. Species of rockfish and lingcod varied in trophic and size responses, indicating that life-history traits play an important role in predicting MPA effects. These results may suggest early changes in trophic behavior of slow-growing rockfish due to predation risk by faster growing higher trophic level predators such as lingcod inside MPAs established on temperate reefs. Consequently, spatial protection may restore both the trophic and behavioral roles of previously fished consumers earlier and in measurable ways sooner than observable changes in abundance and size.

Temperate zone coastal seascapes: seascape patterning and adjacent seagrass habitat shape the distribution of rocky reef fish assemblages

Whilst the composition and arrangement of habitats within landscape mosaics are known to be important determinants of biodiversity patterns, the influence of seascape patterning and connectivity on temperate reef fish assemblages remains largely unknown. We examined how habitat patterns at multiple spatial scales (100–1000 m) explained the abundance and diversity of temperate reef fish in a reef-seagrass dominated seascape. Fish assemblages were surveyed using remote underwater videos deployed on 22 reefs in Jervis Bay, NSW, Australia. Using full-subset GAMMs, we investigated if habitat area, edge, structural connectivity and a metric for habitat diversity (Shannon’s diversity index) of reef and seagrass can predict variations in a temperate reef fish assemblage. A key finding of the study was that temperate reefs close ( 6.25 ha) seagrass meadows contained greater abundance and diversity of fish. A consistent negative correlation was also found between reef area (> 0.01 ha) and the fish assemblage. The influence of seascape metrics on the abundance of fishes varied with functional traits (trophic groups, mobility and habitat associations). Fish-seascape relationships occurred at a range of spatial scales with no single scale being solely important for structuring the fish assemblage. We demonstrate that it is important not to view reef habitats in isolation, rather consider a reefs context to adjacent seagrass when predicting the distribution of temperate reef fish. This finding improves current understanding of the multi-scale factors structuring temperate reef fish assemblages and highlights the importance of reef-seagrass connectivty for the management of temperate marine ecosystems.