Crossing Invisible Boundaries: the Effectiveness of the Langebaan Lagoon Marine Protected Area as a Harvest Refuge for a Migratory Fish Species in South Africa

Abstract:  The application of no-take areas in fisheries remains controversial. Critics argue that many targeted species are too mobile to benefit from area protection and that no-take areas are only appropriate for resident species. The degree of protection does not depend on the size of the no-take area but rather on the time fish reside inside its boundaries during key life-history events (i.e., spawning) and during periods of peak fishing activity. We evaluated the potential of a small no-take marine protected area (MPA) inside a coastal embayment as a harvest refuge for a mobile, possibly migratory, long-lived fish species. We used acoustic telemetry to track movements of 30 transmitter-tagged white stumpnose (Rhabdosargus globiceps) across and on both sides of the boundary of a small (34 km²) no-take area over a full year. Being landlocked on 3 sides, the location of the MPA inside the lagoon made it practical to detect all boundary crossings and to calculate the time individual fish used the MPA. We detected frequent movements across the boundary, with strong seasonal and individual variations. There were significant differences in MPA use patterns between fish from different release areas. The time spent in the MPA by individual fish during summer (mean 50%; max 98%) was out of proportion with the size of that area (4% of total habitat). Summer coincided with peak recreational fishing activity and with the spawning season of this species. The small MPA provided a refuge for a part of the spawning stock of white stumpnose. Our findings suggest that if strategically placed, a small no-take area can be effective in protecting mobile species and that models of spillover from no-take areas should account for seasonal and individual variation in area use and the spatiotemporal distribution of fish and fishers.     

Seasonal,diel, and tidal movements of green jobfish (<Emphasis Type="Italic">Aprion virescens</Emphasis>, Lutjanidae) at remote Hawaiian atolls: implications for marine protected area design

Empirical data quantifying the long-term movement patterns of coral reef top predators are needed in order to design marine protected areas (MPAs) that will provide these fishes with effective, long-term protection. Acoustic telemetry was used to quantify the movements of a large coral reef top predator (Aprion virescens, Lutjanidae; Hawaiian name ‘uku’) at five atolls in the Northwestern Hawaiian Islands Marine National Monument (NWHIMNM) from May 2005 to September 2006. The study atolls were located between 23.8°N, 166.2°W and 28.5°N, 178.3°W, and were separated from their nearest receiver-equipped neighbor by distances ranging from 100 to 478 km. No inter-atoll movements by uku were detected but individuals were seasonally site-attached to core activity areas of up to 12 km in length, and ranged up to 19 km across atolls. Within their core areas, tagged uku exhibited diel and tidal habitat shifts, with the latter resulting in round trips of up to 24 km in 24 h. Seasonal uku migrations resulted in extended winter (October–April) absences from summer (May–September) core activity areas and may be linked to summer spawning. Large MPAs (i.e., entire islands, atolls or banks) would probably be required for full protection of resident populations of adult uku, but such ‘island-scale’ MPAs will not benefit fisheries unless there is significant larval supply from MPAs to neighboring fished areas, or adult emigration over time scales exceeding the 16-month monitoring period of this study. A mixed management strategy of combining smaller MPAs with conventional measures (e.g., minimum size limits, catch, and effort restrictions) may be the best approach for sustaining uku fisheries. However, this would still require relatively large MPAs (12 km in length) to contain uku short-term (diel and tidal) movements, and seasonal migrations would still take uku beyond the boundaries of MPAs of this size. These fluxes across MPA boundaries could supply fish to fisheries but, if high exploitation rates exist, fishing could eliminate key MPA benefits such as increased numbers of large, highly fecund individuals. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Movement patterns of young Caribbean reef sharks, Carcharhinus perezi, at Fernando de Noronha Archipelago, Brazil: the potential of marine protected areas for conservation of a nursery ground

The movement patterns and long-term site-fidelity of primarily juvenile Caribbean reef sharks, Carcharhinus perezi, were investigated using tag-recapture and automated telemetry at an insular nursery area, the Fernando de Noronha Archipelago, Brazil. Of the 143 externally tagged juvenile sharks (<110 cm), 22 (15.3%) were recaptured between 0 and 5 km from the site of tagging after 5–800 days at liberty, suggesting some site-fidelity in young individuals of this species. Site-fidelity and movement patterns of ten juvenile sharks ranging from 78 to 110 cm total length (TL) and one opportunistically captured adult female (224 cm TL) were also investigated for periods of up to 2 years with an array of automated telemetry receivers. Tagging and telemetry data from both inside and outside a marine protected area (MPA) show that shark abundance and activity is greatest along the part of the archipelago’s coastline least disturbed by human activity. Telemetry tracking also showed that juvenile reef sharks demonstrated a high degree of site-fidelity and occupied specific locations along the coast throughout the year, with some evidence of an increase in activity space with ontogeny. Sharks appeared to range more widely at night and there were no seasonal variations in habitat use. Our results suggest that MPAs may be a useful conservation tool to protect young C. perezi and potentially other reef-dwelling carcharhinid sharks during their early life history.     

Use of pelagic prey subsidies by demersal predators in rocky reefs: insight from movement patterns of lingcod

Allochthonous subsidies of energy and nutrients can affect community structure in patchy marine habitats, including rocky reefs, and their ecological consequences may depend on the mechanism of energy transfer. Lingcod (Ophiodon elongatus) are demersal predators that trophically link nearshore rocky reefs with offshore pelagic habitats through consumption of pelagic fishes. We quantified lingcod habitat use and movement patterns to make inferences about the temporal and spatial conditions under which lingcod may acquire pelagic prey. Lingcod maintained small home ranges (21,272 ± 13,630 m²) within a rocky reef in the San Juan Archipelago, Washington; eight of nine individuals used rocky habitat exclusively. Depths occupied by lingcod (0–50 m) coincided with pelagic fish distribution on the rocky reef; however, diel patterns in lingcod activity varied inversely with occurrence of pelagic fishes on the reef. Our findings suggest that the pelagic subsidy to lingcod is not strongly mediated through directed off-reef foraging by lingcod.     

Combined use of eDNA metabarcoding and video surveillance for the assessment of fish biodiversity

Monitoring communities of fish is important for the management and sustainability of fisheries and marine ecosystems. Baited remote underwater video systems (BRUVs) are among the most effective nondestructive techniques for sampling bony fishes and elasmobranchs (sharks, rays, and skates). However, BRUVs sample visually conspicuous biota; hence, some taxa are undersampled or not recorded at all. We compared the diversity of fishes characterized using BRUVs with diversity detected via environmental DNA (eDNA) metabarcoding. We sampled seawater and captured BRUVs imagery at 48 locales that included reef and seagrass beds inside and outside a marine reserve (Jurien Bay in Western Australia). Eighty-two fish genera from 13 orders were detected, and the community of fishes described using eDNA and BRUVs combined yielded >30% more generic richness than when either method was used alone. Rather than detecting a homogenous genetic signature, the eDNA assemblages mirrored the BRUVs’ spatial explicitness; differentiation of taxa between seagrass and reef was clear despite the relatively small geographical scale of the study site (∼35 km²). Taxa that were not sampled by one approach, due to limitations and biases intrinsic to the method, were often detected with the other. Therefore, using BRUVs and eDNA in concert provides a more holistic view of vertebrate marine communities across habitats. Both methods are noninvasive, which enhances their potential for widespread implementation in the surveillance of marine ecosystems.     

Influence of habitat on abundance and size structure of a large temperate-reef fish, Achoerodus viridis (Pisces: Labridae)

The relationship between densities of Achoerodus viridis (Pisces: Labridae) and reef habitats at various localities within New South Wales (NSW), Australia was examined. Types of habitats were quantified at inner, mid and outer estuarine locations in each of two estuaries (Botany Bay and Port Jackson) to determine whether purported patterns of movement from estuaries could be related to differences in habitat. Although the same types of habitat were generally found at all locations, differences in the proportion of habitat types were found between shallow and deep reefs and among inner, mid and outer estuarine locations for both estuaries. Shallow habitats were usually dominated by Ecklonia radiata, turf and/or fringe habitat in Botany Bay, whereas deep sites were generally dominated by urchin-grazed barrens habitat and, sometimes, sponge- and ascidian-dominated deep reef. Shallow sites in Port Jackson were dominated by a mixture of habitats, as were deep reefs at mid-estuarine locations. Other deep reefs in Port Jackson were dominated by E. radiata (inner estuarine) or barrens (outer estuarine) habitat. Thus, patterns of habitat cover were not consistent between estuaries and numbers of fish could not be related to proportional representation of habitat on reefs along estuarine gradients. Univariate and multivariate analyses showed that there was little evidence that any size class of fish was correlated with the proportional representation of a particular habitat or group of habitats. Counts of fish that focused on barrens and E. radiata forest habitats over a period of 10 yr showed that similar numbers and all sizes of fish were found in the two types of habitat. Greater numbers of small fish were, however, found in the E. radiata forest habitat than in the barrens habitat. Estimates of abundance along the coast of NSW (100s to 1000 km) in a range of habitats (e.g. ascidian-dominated reef, kelp forest, urchin-grazed barrens) showed that there was no indication that a particular habitat consistently had greater numbers of A. viridis than other habitats. Therefore, A. viridis of a range of sizes appears to be flexible in its use of habitats on reefs. Received: 24 December 1997 / Accepted: 23 June 1998     

Assessing the current state of ecological connectivity in a large marine protected area system

The establishment of marine protected areas (MPAs) is a critical step in ensuring the continued persistence of marine biodiversity. Although the area protected in MPAs is growing, the movement of individuals (or larvae) among MPAs, termed connectivity, has only recently been included as an objective of many MPAs. As such, assessing connectivity is often neglected or oversimplified in the planning process. For promoting population persistence, it is important to ensure that protected areas in a system are functionally connected through dispersal or adult movement. We devised a multi-species model of larval dispersal for the Australian marine environment to evaluate how much local scale connectivity is protected in MPAs and determine whether the extensive system of MPAs truly functions as a network. We focused on non-migratory species with simplified larval behaviors (i.e., passive larval dispersal) (e.g., no explicit vertical migration) as an illustration. Of all the MPAs analyzed (approximately 2.7 million km²), outside the Great Barrier Reef and Ningaloo Reef, <50% of MPAs (46-80% of total MPA area depending on the species considered) were functionally connected. Our results suggest that Australia's MPA system cannot be referred to as a single network, but rather a collection of numerous smaller networks delineated by natural breaks in the connectivity of reef habitat. Depending on the dispersal capacity of the taxa of interest, there may be between 25 and 47 individual ecological networks distributed across the Australian marine environment. The need to first assess the underlying natural connectivity of a study system prior to implementing new MPAs represents a key research priority for strategically enlarging MPA networks. Our findings highlight the benefits of integrating multi-species connectivity into conservation planning to identify opportunities to better incorporate connectivity into the design of MPA systems and thus to increase their capacity to support long-term, sustainable biodiversity outcomes.     

Temperate marine reserves enhance targeted but not untargeted fishes in multiple no-take MPAs.

Although many papers report the effects of no-take marine protected areas (MPAs or reserves), scientifically rigorous empirical studies are rare, particularly for temperate reef fishes. We evaluated the responses of fish populations to protection from fishing in reserves by comparing densities and sizes inside and outside of five no-take reserves in southern California, USA. Our results are robust because we compared responses across multiple rocky-reef reserves in two different years and controlled for possible site differences by (a) ensuring that habitat characteristics were the same inside and outside reserves, and (b) sampling species that are not targeted, which would not be expected to have a direct response to fishing. We compared fish density and size and calculated biomass and egg production across all five sites. Fishes targeted by recreational and/or commercial fisheries consistently exhibited increases in mean density (150%), size (30%), biomass (440%), and egg production (730%) inside reserves. Reserve effects were greatest for legal-sized targeted fishes: significantly greater densities were found exclusively inside reserves for targeted species (580%), the largest size classes existed only inside reserves, and mean biomass was 1000% higher. These responses were unlikely to have been caused by habitat differences because there were no significant differences in habitat characteristics between reserve and control locations. Densities of non-targeted species did not differ between reserve and non-reserve locations, further supporting the conclusions that differences in targeted species between reserve and control locations were due to harvesting rather than site-specific effects. Although MPAs cannot replace traditional fisheries management, the concentration of increased biomass and egg production is a unique MPA benefit that serves both reserves and fisheries. Scientifically rigorous studies that include multiple reserves, such as this study, are needed to inform management and policy decisions.     

Offshore distributional patterns of Hawaiian fish larvae

An analysis of ichthyoplankton samples based on relative abundance reveals pronounced inshore/offshore distributional gradients for most Hawaiian fish larvae. Larvae of pelagic bay species are found almost exclusively in semi-enclosed bays and estuaries. Larvae of pelagic neritic species are more or less uniformly distributed with distance from shore. The larvae of reef species with non-pelagic eggs are most abundant close to shore, while those of reef species with pelagic eggs are most abundant offshore. Finally, the larvae of offshore (primarily mesopelagic) species show no clear pattern but frequently occur in high numbers nearshore. Within any group, variation in pattern was often evident; for example, although Hawaiian fishes of both the families Labridae and Mullidae spawn pelagic eggs, larvae of the former had not peaked in abundance 12 km from shore while larvae of the latter had peaked between 0.5 and 2 km. Some larvae which occur offshore are highly specialized morphologically for a pelagic existence (e.g. Chaetodontidae, which is illustrated) while others are little modified (e.g. Labridae). These findings indicate ichthyoplankton surveys in tropical areas must sample offshore areas in addition to the inshore adult habitat to obtain a complete picture.Hawaii Institute of Marine Biology Contribution No. 484.     

The application of predicted habitat models to investigate the spatial ecology of demersal fish assemblages

Benthic habitats are known to influence the abundance and richness of demersal fish assemblages; however, little is known about how habitat structure and composition influences these distributions at very fine scales. We examined how the benthic environment structures marine fish assemblages using high-resolution bathymetry and accurate predicted benthic habitat maps. Areas characterised by a mosaic of habitat patches supported the highest richness of demersal fishes. A total of 37.4% of the variation in the distribution of the fish assemblage was attributed to 6 significant variables. Depth explained 23.0% of the variation, with the boulders explaining 12.6% and relief 1.4%. The remaining measures (seawhips, light/exposure and solid reef) provided a small (<1.0%) but significant contribution. Identifying components of the benthic environment important in structuring fish assemblages and understanding how they influence the spatial distribution of marine fishes is imperative for better management of demersal fish populations.     

Defining Critical Habitats of Threatened and Endemic Reef Fishes with a Multivariate Approach

Understanding critical habitats of threatened and endemic animals is essential for mitigating extinction risks, developing recovery plans, and siting reserves, but assessment methods are generally lacking. We evaluated critical habitats of 8 threatened or endemic fish species on coral and rocky reefs of subtropical eastern Australia, by measuring physical and substratum‐type variables of habitats at fish sightings. We used nonmetric and metric multidimensional scaling (nMDS, mMDS), Analysis of similarities (ANOSIM), similarity percentages analysis (SIMPER), permutational analysis of multivariate dispersions (PERMDISP), and other multivariate tools to distinguish critical habitats. Niche breadth was widest for 2 endemic wrasses, and reef inclination was important for several species, often found in relatively deep microhabitats. Critical habitats of mainland reef species included small caves or habitat‐forming hosts such as gorgonian corals and black coral trees. Hard corals appeared important for reef fishes at Lord Howe Island, and red algae for mainland reef fishes. A wide range of habitat variables are required to assess critical habitats owing to varied affinities of species to different habitat features. We advocate assessments of critical habitats matched to the spatial scale used by the animals and a combination of multivariate methods. Our multivariate approach furnishes a general template for assessing the critical habitats of species, understanding how these vary among species, and determining differences in the degree of habitat specificity. Definición de Hábitats Críticos para Peces Arrecifales Amenazados y Endémicos Mediante un Método Multivariado     

Effects of Human Population Density and Proximity to Markets on Coral Reef Fishes Vulnerable to Extinction by Fishing

Coral reef fisheries are crucial to the livelihoods of tens of millions of people; yet, widespread habitat degradation and unsustainable fishing are causing severe depletion of stocks of reef fish. Understanding how social and economic factors, such as human population density, access to external markets, and modernization interact with fishing and habitat degradation to affect fish stocks is vital to sustainable management of coral reef fisheries. We used fish survey data, national social and economic data, and path analyses to assess whether these factors explain variation in biomass of coral reef fishes among 25 sites in Solomon Islands. We categorized fishes into 3 groups on the basis of life‐history characteristics associated with vulnerability to extinction by fishing (high, medium, and low vulnerability). The biomass of fish with low vulnerability was positively related to habitat condition. The biomass of fishes with high vulnerability was negatively related to fishing conducted with efficient gear. Use of efficient gear, in turn, was strongly and positively related to both population density and market proximity. This result suggests local population pressure and external markets have additive negative effects on vulnerable reef fish. Biomass of the fish of medium vulnerability was not explained by fishing intensity or habitat condition, which suggests these species may be relatively resilient to both habitat degradation and fishing. Efectos de la Densidad de Poblaciones Humanas y la Proximidad del Mercado sobre Peces de Arrecifes de Coral Vulnerables a la Extinción     

Relative influence of environmental factors and fishing on coral reef fish assemblages

Understanding whether assemblages of species respond more strongly to bottom-up (availability of trophic resources or habitats) or top-down (predation pressure) processes is important for effective management of resources and ecosystems. We determined the relative influence of environmental factors and predation by humans in shaping the density, biomass, and species richness of 4 medium-bodied (10–40 cm total length [TL]) coral reef fish groups targeted by fishers (mesopredators, planktivores, grazer and detritivores, and scrapers) and the density of 2 groups not targeted by fishers (invertivores, small fish ≤10 cm TL) in the central Philippines. Boosted regression trees were used to model the response of each fish group to 21 predictor variables: 13 habitat variables, 5 island variables, and 3 fishing variables (no-take marine reserve [NTMR] presence or absence, NTMR size, and NTMR age). Targeted and nontargeted fish groups responded most strongly to habitat variables, then island variables. Fishing (NTMR) variables generally had less influence on fish groups. Of the habitat variables, live hard coral cover, structural complexity or habitat complexity index, and depth had the greatest effects on density, biomass, and species richness of targeted fish groups and on the density of nontargeted fishes. Of the island variables, proximity to the nearest river and island elevation had the most influence on fish groups. The NTMRs affected only fishes targeted by fishers; NTMR size positively correlated with density, biomass, and species richness of targeted fishes, particularly mesopredatory, and grazing and detritivorous fishes. Importantly, NTMRs as small as 15 ha positively affected medium-bodied fishes. This finding provides reassurance for regions that have invested in small-scale community-managed NTMRs. However, management strategies that integrate sound coastal land-use practices to conserve adjacent reef fish habitat, strategic NTMR placement, and establishment of larger NTMRs will be crucial for maintaining biodiversity and fisheries.     

Use of Habitats as Surrogates of Biodiversity for Efficient Coral Reef Conservation Planning in Pacific Ocean Islands

Abstract: Marine protected areas (MPAs) have been highlighted as a means toward effective conservation of coral reefs. New strategies are required to more effectively select MPA locations and increase the pace of their implementation. Many criteria exist to design MPA networks, but generally, it is recommended that networks conserve a diversity of species selected for, among other attributes, their representativeness, rarity, or endemicity. Because knowledge of species’ spatial distribution remains scarce, efficient surrogates are urgently needed. We used five different levels of habitat maps and six spatial scales of analysis to identify under which circumstances habitat data used to design MPA networks for Wallis Island provided better representation of species than random choice alone. Protected‐area site selections were derived from a rarity–complementarity algorithm. Habitat surrogacy was tested for commercial fish species, all fish species, commercially harvested invertebrates, corals, and algae species. Efficiency of habitat surrogacy varied by species group, type of habitat map, and spatial scale of analysis. Maps with the highest habitat thematic complexity provided better surrogates than simpler maps and were more robust to changes in spatial scales. Surrogates were most efficient for commercial fishes, corals, and algae but not for commercial invertebrates. Conversely, other measurements of species‐habitat associations, such as richness congruence and composition similarities provided weak results. We provide, in part, a habitat‐mapping methodology for designation of MPAs for Pacific Ocean islands that are characterized by habitat zonations similar to Wallis. Given the increasing availability and affordability of space‐borne imagery to map habitats, our approach could appreciably facilitate and improve current approaches to coral reef conservation and enhance MPA implementation.     

Population connectivity in the temperate damselfish <Emphasis Type="Italic">Parma microlepis</Emphasis>: analyses of genetic structure across multiple spatial scales

This study investigated the utility of microsatellite markers for providing information on levels of population connectivity for a low dispersing reef fish in New South Wales (NSW), Australia, at scales ≤400 km. It was hypothesized that the temperate damselfish Parma microlepis, which produces benthic eggs and has limited post-settlement dispersal, would exhibit spatial genetic structure and a significant pattern of isolation-by-distance (IBD). A fully nested hierarchical sampling design incorporating three spatial scales (sites, location and regions, separated by 1–2, 10–50 and 70–80 km respectively) was used to determine genetic variability at seven microsatellite loci. Broad-scale genetic homogeneity and lack of IBD was well supported by single and multi-locus analyses. The proportion of the total genetic variation attributable to differences among regions, locations or sites was effectively zero (Φ/R-statistics ≤0.007). The geographic distribution of genetic diversity and levels of polymorphism (H _E 0.21–0.95) indicate high mutation rates, large effective population sizes, and high rates of gene flow. Significant gene flow may be driven by factors influencing pre-settlement dispersal, including the East Australian Current (EAC) and habitat continuity. Genetic connectivity may not reflect demographically important connectivity, but does imply that P. microlepis populations are well connected from an evolutionary perspective. Total observed genetic diversity was accounted for within 1–2 km of reef and could be represented within small Marine Protected Areas. Reef fishes in NSW which have life histories similar to P. microlepis (e.g. pre-settlement durations ≥2 weeks) are also likely to exhibit genetic homogeneity. Genetic markers are, therefore, most likely to provide information on demographically relevant connectivity for species with lower dispersal capabilities, small population sizes, short life spans, and whose habitats are rare, or patchily distributed along-shore. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Size-dependent behavior of tuna in an array of fish aggregating devices (FADs)

Several lines of evidence indicate that aggregations of yellowfin tuna associated with floating objects are more frequently composed of small animals than larger ones. Also, the diet of small yellowfin tuna caught at anchored fish aggregating devices (FADs) around Oahu, Hawaii, was found to shift quite rapidly when these fish reached approximately 50 cm FL. In order to test for ontogenetic changes in aggregation behavior, we tagged and released two distinct size classes of yellowfin tuna in an array of anchored FADs around Oahu, Hawaii. Twenty-four yellowfin tuna 30–39 cm FL and 16 yellowfin tuna 63–83 cm FL were tagged with acoustic transmitters and released near anchored FADs equipped with automated acoustic receivers. Fish in the smaller size class stayed about 2.5 times longer at individual FADs than the larger fish (mean 4.05 days vs. 1.65 days) and displayed larger horizontal movements within the array. However, the durations of unassociated phases, residence times in the entire FAD array, percentage of time spent associated with FADs and numbers of movements between FADs did not show any difference between the two size groups. The observed size-dependent behavior is discussed in terms of physiological abilities, diet segregation and anti-predator behavior.     

Latitudinal variation in abundance of herbivorous fishes: a comparison of temperate and tropical reefs

The aim of the study was to provide comparable estimates of abundance of herbivorous reef fishes at temperate and tropical localities using a standardized methodology. Faunas of herbivorous fish were sampled on the rocky reefs of temperate northern New Zealand and on the coral reefs of the northern Great Barrier Reef (GBR), Australia, and the San Blas Archipelago in the Caribbean. A pilot study established the most appropriate habitat setting and the scale and magnitude of replication for the sampling program in temperate waters. Herbivorous fishes, including members of families endemic to the southern hemisphere (Odacidae and Aplodactylidae), were most abundant in turbulent, shallow water (0 to 6 m) and had patchy distributions within this habitat. A hierarchical sampling program using 10-min transect counts within the 0 to 6 m depth stratum examined abundance patterns at a range of spatial scales including mainland and island coasts, localities separated by up to 100 km and sites separated by up to 10 km. This program identified a characteristic fauna of seven species of herbivorous fishes with mean total abundances ranging from 23 to 30 individuals per 10-min transect. Species composition of the fauna varied between islands and coasts. A similar methodology was used to sample the major families of herbivorous fish in a number of sites in each of the tropical regions. These sampling programs revealed a fauna dominated by acanthurids and scarids in both the GBR and Caribbean localities. Estimates of abundance from these regions were similar, with a mean of 108 individuals recorded on the GBR and 129 per 10-min transect in the Caribbean. Species richness varied between each region, with 44 taxa recorded from the GBR and 11 from the Caribbean. Abundances of temperate water herbivores in New Zealand were found to be 75 to 80% lower than those recorded from shallow water habitats sampled on coral reefs. This was not related to species richness, since both New Zealand and the Caribbean locality had patterns of low richness. We suggest that the differences in abundance found by our study between temperate and tropical regions are not restricted to herbivorous fishes, but are representative of general latitudinal trends in reef fish faunas. Received: 4 November 1996 / Accepted: 15 December 1996     

The use of clear-water non-estuarine mangroves by reef fishes on the Great Barrier Reef

Within the tropics, mangroves and coral reefs represent highly productive biomes. Although these habitats are often within close proximity, the role and importance of mangrove habitats for reef fish species remains unclear. Throughout the Indo-Pacific, reef fish species appear to have few links with estuarine mangrove habitats. In contrast, clear-water non-estuarine mangrove habitats throughout the Caribbean support many reef fish species and may be fundamental for sustaining reef fish populations. But how important are clear-water non-estuarine mangroves for reef fishes within the Indo-Pacific? Using visual surveys during diurnal high tide, the fish assemblages inhabiting clear-water mangrove and adjacent reef habitats of Orpheus Island, Great Barrier Reef, were recorded. Of the 188 species of fishes that were recorded, only 38 were observed to inhabit both habitats. Of these, only eight were observed more than five times within each habitat. These observations provide little indication that the clear-water mangroves are an important habitat for reef fish species. In addition, although based on just a 3-month survey period, we found little evidence to suggest that these areas are important nurseries for reef fish species. The clear-water mangroves of Orpheus Island may, however, provide an additional foraging area for the few reef fish species that were observed to utilize these habitats during high tide. The difference in the importance of clear-water mangroves for reef fishes within this study compared with clear-water mangrove counterparts within the Caribbean is surprising. Although only preliminary, our observations would support suggestions that the patterns reflect the different hydrological characteristics and evolutionary histories of these two biogeographic regions.