Mark E. Monaco

Biologically-Based Estuarine Salinity Zones Derived From a Multivariate Analysis

Principal Component Analysis (PCA) was used to derive estuarine salinity zones based on field data on the salinity ranges of 316 species/life stages in the mid-Atlantic region (chiefly Chesapeake Bay and Delaware Bay species). Application of PCA to the data matrix showed that the structure underlying a diversity of salinity distributions could be represented by only five Principal Components corresponding to five overlapping salinity zones: freshwater to 4‰, 2–14‰, 11–18‰, 16–27‰ to marine. The derived salinity zonation showed both differences and similarities to the Venice System of estuarine zonation. However, unlike the static and essentially descriptive Venice System, the new method will allow researchers to establish biologically-relevant local salinity zones, and then develop hypotheses about the processes that give rise to the resulting patterns. Examples of this procedure are given for the mid-Atlantic region. The method used here may also be useful for studying distributions across other environmental gradients, such as temperature, pH, substrate, turbidity, vegetation, or latitude.

COUPLING ECOLOGY AND GIS TO EVALUATE EFFICACY OF MARINE PROTECTED AREAS IN HAWAII

In order to properly determine the efficacy of marine protected areas (MPAs), a seascape perspective that integrates ecosystem elements at the appropriate ecological scale is necessary. Over the past four decades, Hawaii has developed a system of 11 Marine Life Conservation Districts (MLCDs) to conserve and replenish marine resources around the state. Initially established to provide opportunities for public interaction with the marine environment, these MLCDs vary in size, habitat quality, and management regimes, providing an excellent opportunity to test hypotheses concerning MPA design and function using multiple discrete sampling units. Digital benthic habitat maps for all MLCDs and adjacent habitats were used to evaluate the efficacy of existing MLCDs using a spatially explicit stratified random sampling design. Analysis of benthic cover validated the a priori classification of habitat types and provided justification for using these habitat strata to conduct stratified random sampling and analyses of fish habitat utilization patterns. Results showed that a number of fish assemblage characteristics (e.g., species richness, biomass, diversity) vary among habitat types, but were significantly higher in MLCDs compared with adjacent fished areas across all habitat types. Overall fish biomass was 2.6 times greater in the MLCDs compared to open areas. In addition, apex predators and other species were more abundant and larger in the MLCDs, illustrating the effectiveness of these closures in conserving fish populations within their boundaries. Habitat type, protected area size, and level of protection from fishing were all important determinates of MLCD effectiveness with respect to their associated fish assemblages. Although size of these protected areas was positively correlated with a number of fish assemblage characteristics, all appear too small to have any measurable influence on the adjacent fished areas. These protected areas were not designed for biodiversity conservation or fisheries enhancement yet still provide varying degrees of protection for fish populations within their boundaries. Implementing this type of biogeographic process, using remote sensing technology and sampling across the range of habitats present within the seascape, provides a robust evaluation of existing MPAs and can help to define ecologically relevant boundaries for future MPA design in a range of locations.

Benthic Mapping Using Sonar, Video Transects, and an Innovative Approach to Accuracy Assessment: A Characterization of Bottom Features in the Georgia Bight

Abstract Benthic maps provide the spatial framework for many science and management activities in coastal areas such as identification and protection of fish distributions and associated habitat as well as for monitoring changes in benthos and fish communities. To meet this need at Grays Reef National Marine Sanctuary off the Georgia, U.S.A., coast, we created fine-scale benthic maps by visual interpretation of sonar imagery within a geographic information system. The major bottom types in the sanctuary—flat sand, rippled sand, hard bottom that is sparsely colonized with sessile invertebrates, and densely colonized hard bottom—were delineated through combined analysis of backscatter from side-scan sonar, bathymetry from multibeam sonar, scuba surveys, and video transects. Maps showed that unconsolidated sediments cover 75% of the bottom of this region; 8% occurs as flat sand plains with obvious burrowing and reworking of surface material by mobile benthic invertebrates, whereas 67% occurs as rippled sand without such fauna. The rest of the sanctuary consists of limestone bottom in two types of formations; either flat, sparsely colonized regions (25% of the sanctuarys total area) or as vertical ledges that are densely colonized with a diverse fauna of sessile invertebrates (<1%). Despite their limited area, these 0.5–2-m-tall ledge features harbor the majority of the sanctuarys biodiversity and biomass of both sessile invertebrates as well as ichthyofauna. A modified accuracy assessment procedure was used to account for spatial autocorrelation in the validation data and to separate thematic from positional accuracy. Overall thematic accuracy of maps is 95% for those areas of the map in which thematic accuracy and positional accuracy could be separated (87% of the mapped area). This fine-scale characterization provides a benthic inventory for a marine sanctuary and novel methods for mapping using sonar and accuracy assessment using transects.

Length-based assessment of sustainability benchmarks for coral reef fishes in Puerto Rico

SUMMARY The sustainability of multispecies coral reef fisheries is a key conservation concern given their economic and ecological importance. Empirical estimation and numerical model analyses were conducted to evaluate exploitation status via resource reference points (or sustainability benchmarks) for coral reef fishes of the snapper-grouper complex in Puerto Rico. Mean size (¯ L, in length) of animals in the exploited part of the population was estimated from fishery-dependent and fishery-independent size composition data and used as an indicator variable of exploitation rates. In application, fishing mortality rates estimated from ¯ L of various data sources were comparable. Of the 25 reef fish species assessed, 16 were below 30% spawning potential ratio (SPR), six were above 30% SPR, and three could not be reliably determined owing to low sample sizes. These findings indicate that a majority ofsnapper-grouperspeciesinPuertoRicoarecurrently fished at unsustainable levels.

Fish with Chips: Tracking Reef Fish Movements to Evaluate Size and Connectivity of Caribbean Marine Protected Areas

Coral reefs and associated fish populations have experienced rapid decline in the Caribbean region and marine protected areas (MPAs) have been widely implemented to address this decline. The performance of no-take MPAs (i.e., marine reserves) for protecting and rebuilding fish populations is influenced by the movement of animals within and across their boundaries. Very little is known about Caribbean reef fish movements creating a critical knowledge gap that can impede effective MPA design, performance and evaluation. Using miniature implanted acoustic transmitters and a fixed acoustic receiver array, we address three key questions: How far can reef fish move? Does connectivity exist between adjacent MPAs? Does existing MPA size match the spatial scale of reef fish movements? We show that many reef fishes are capable of traveling far greater distances and in shorter duration than was previously known. Across the Puerto Rican Shelf, more than half of our 163 tagged fish (18 species of 10 families) moved distances greater than 1 km with three fish moving more than 10 km in a single day and a quarter spending time outside of MPAs. We provide direct evidence of ecological connectivity across a network of MPAs, including estimated movements of more than 40 km connecting a nearshore MPA with a shelf-edge spawning aggregation. Most tagged fish showed high fidelity to MPAs, but also spent time outside MPAs, potentially contributing to spillover. Three-quarters of our fish were capable of traveling distances that would take them beyond the protection offered by at least 40–64% of the existing eastern Caribbean MPAs. We recommend that key species movement patterns be used to inform and evaluate MPA functionality and design, particularly size and shape. A re-scaling of our perception of Caribbean reef fish mobility and habitat use is imperative, with important implications for ecology and management effectiveness.

Nocturnal fish movement and trophic flow across habitat boundaries in a coral reef ecosystem (SW Puerto Rico)

Abstract. Few studies have quantified the extent of nocturnal cross-habitat movements for fish, or the influence of habitat adjacencies on nutrient flows and trophodynamics. To investigate the patterns of nocturnal cross-boundary movements of fish and quantify trophic connectivity, fish were sampled at night with gillnets set along the boundaries between dominant habitat types (coral reef/seagrass and mangrove/ seagrass) in southwestern Puerto Rico. Fish movement across adjacent boundary patches were equivalent at both coral reefs and mangroves. Prey biomass transfer was greater from seagrass to coral reefs (0.016 kg/km) and from mangroves to seagrass (0.006 kg/km) but not statistically significant, indicating a balance of flow between adjacent habitats. Pelagic species (jacks, sharks, rays) accounted for 37% of prey biomass transport at coral reef/seagrass and 46% at mangrove/seagrass while grunts and snappers accounted for 7% and 15%, respectively. This study indicated that coral reefs and mangroves serve as a feeding area for a wide range of multi-habitat fish species. Crabs were the most frequent prey item in fish leaving coral reefs while molluscs were observed slightly more frequently than crabs in fish entering coral reefs. For most prey types, biomass exported from mangroves was greater than biomass imported. The information on direction of fish movement together with analysis of prey data provided strong evidence of ecological linkages between distinct adjacent habitat types and highlighted the need for greater inclusion of a mosaic of multiple habitats when attempting to understand ecosystem function including the spatial transfer of energy across the seascape.

Long-term monitoring of habitats and reef fish found inside and outside the U.S. Virgin Islands Coral Reef National Monument: A comparative assessment

Abstract. The primary objective of this study was to assess the efficacy of the Virgin Islands Coral Reef National Monument (VICR), a marine protected area in St John, US Virgin Islands. Surveys of habitat and fishes inside and outside of VICR were conducted in 2003–2008. Areas outside the VICR had significantly more scleractinian corals, greater habitat complexity, and greater species richness and density of reef fishes than areas inside., Areas inside and outside the VICR exhibited significant decreases in percent scleractinian coral coverage over the study period. A contrasting trend of increasing macroalgal cover was also observed. No clear effect of the severe 2005 coral bleaching event was observed suggesting other causal factors. No obvious trends in the fish community were observed across the study period. The significant decline in habitat condition, coupled with the initial incorporation of some of the more degraded reefs into the marine protected area may result in a longer time period necessary to detect positive changes in the St. John coral reef ecosystem and associated reef fish abundance and community structure.