A review of the ecological effectiveness of subtidal marine reserves in Central California, Part I: Synopsis of scientific investigations

Marine reserves, often referred to as no-take MPAs, are defined as areas within which human activities that can result in the removal or alteration of biotic and abiotic components of an ecosystem are prohibited or greatly restricted (NRC 2001). Activities typically curtailed within a marine reserve are extraction of organisms (e.g., commercial and recreational fishing, kelp harvesting, commercial collecting), mariculture, and those activities that can alter oceanographic or geologic attributes of the habitat (e.g., mining, shore-based industrial-related intake and discharges of seawater and effluent). Usually, marine reserves are established to conserve biodiversity or enhance nearby fishery resources. Thus, goals and objectives of marine reserves can be inferred, even if they are not specifically articulated at the time of reserve formation. In this report, we review information about the effectiveness of the three marine reserves in the Monterey Bay National Marine Sanctuary (Hopkins Marine Life Refuge, Point Lobos Ecological Reserve, Big Creek Ecological Reserve), and the one in the Channel Islands National Marine Sanctuary (the natural area on the north side of East Anacapa Island). Our efforts to objectively evaluate reserves in Central California relative to reserve theory were greatly hampered for four primary reasons; (1) few of the existing marine reserves were created with clearly articulated goals or objectives, (2) relatively few studies of the ecological consequences of existing reserves have been conducted, (3) no studies to date encompass the spatial and temporal scope needed to identify ecosystem-wide effects of reserve protection, and (4) there are almost no studies that describe the social and economic consequences of existing reserves. To overcome these obstacles, we used several methods to evaluate the effectiveness of subtidal marine reserves in Central California. We first conducted a literature review to find out what research has been conducted in all marine reserves in Central California (Appendix 1). We then reviewed the scientific literature that relates to marine reserve theory to help define criteria to use as benchmarks for evaluation. A recent National Research Council (2001) report summarized expected reserve benefits and provided the criteria we used for evaluation of effectiveness. The next step was to identify the research projects in this region that collected information in a way that enabled us to evaluate reserve theory relative to marine reserves in Central California. Chapters 1-4 in this report provide summaries of those research projects. Contained within these chapters are evaluations of reserve effectiveness for meeting specific objectives. As few studies exist that pertain to reserve theory in Central California, we reviewed studies of marine reserves in other temperate and tropical ecosystems to determine if there were lessons to be learned from other parts of the world (Chapter 5). We also included a discussion of social and economic considerations germane to the public policy decision-making processes associated with marine reserves (Chapter 6). After reviewing all of these resources, we provided a summary of the ecological benefits that could be expected from existing reserves in Central California. The summary is presented in Part II of this report. (PDF contains 133 pages.

Habitat association, disturbance dynamics, and the role of spatial scale in structuring coral reef fish assemblages

Habitat association, disturbance dynamics, and the role of spatial scale in structuring coral reef fish assemblages. Understanding how patterns and processes at one scale are related to those at other scales is of central importance in developing ecological theory. However, in order for scaling rules to be useful to empirical ecologists, they must have a rational, measurable, and critically examinable basis. In this study I consider the role spatial scale plays in structuring coral reef fish assemblages and how habitat structure may mediate scaling rules for the assemblage.\ud \ud The relationship between a population's mean and variance provide a measure of whether that population is indeed scale dependent. I counted fish and measured habitat variables in 701 transects, allocated across 12 habitat zones. Slopes of the power plots for most species lay between 1 and 2 which indicated that the variance, as a proportion of the mean, of small samples was lower than in large samples and hence scale-dependent. 28% of the variation of the data set was explained by habitat variables which indicated that a large percentage of the scale dependence could be modelled by habitat variables alone.\ud \ud Peaks of variability associated with changes in scale are indicators of the scales at which organisms are spatially structured. It has been hypothesised that coincident variance peaks are indicators of common scales of organisation and thus should also correspond to the scale of maximal correlation. I tested this idea by quantifying fish-habitat associations at different scales on contiguous coral reefs. I mapped fish and habitat to a 3x3m resolution in 24 30x30m grids and then progressively aggregated adjacent squares and recalculated the correlation between fish and benthic cover, physical reef structure, and locality over 9 spatial scales ranging from 9-225m ². Both fish and habitat variables were patchy at the smallest scale, yet maximal correlation occurred at larger scales (>54m ²). A complex suite of responses were found among fish taxa, with some species associated simply with benthic cover and locality, while others were associated with complex interactions between different types of habitat measures. The scale of maximal correlation was not indicative of the scale at which fishes responded to their environment. Maximal correlation was found when the likelihood of the occurrence of a particular fish species and the likelihood of the occurrence of preferred habitat type were symmetrised. In other words, the scale of measurable fish-habitat association was a measurement of the optimal scale at which predictability of fish given habitat type, and predictability of habitat type given fish were maximised.\ud \ud Studies carried out on small patch reefs have provided the basic information from which much ecological theory of coral reef fishes has been derived. However no published studies have attempted to document what scaling effects exist in coral reef systems, and whether we can extrapolate or interpolate between studies carried out on different scales. I mapped randomly selected patch reefs, ranging in size from 0.26m ² to 63.5m ², and censused the resident fish fauna. I then partitioned variation amongst reef area, reef shape and patchiness, and benthic cover. Species responded in a variety of ways to reef parameters. Some species were strongly area-dependent, others were well predicted by reef shape and patchiness, and a considerable number of species were well predicted by the benthic cover of the reef. Further groups of species were associated with combinations of these factors. In order to measure the effect of scaling up or down, I divided the data set into small, medium, and large reefs, recalculated regression equations and measured the predictive ability of each equation. Surprisingly equations derived from the smaller reefs were better predictors of larger reefs than vice versa. As a consequence, the lessons drawn from experiments carried out on small reefs can, in the light of prior information, be cautiously, and with strong caveats, applied to large reefs. Central to these scaling rules is the incorporation of habitat as an explanatory variable.\ud \ud To establish the bounds within which habitat may influence fish assemblage structure, I carried out two experiments. First, I experimentally reduced coral cover in 10x10m quadrats on contiguous reef from 55% to 47%, 43%, and 34% and monitored the assemblage over two years. Contrary to what might be expected from many correlative studies, all fish species considered were resistant, at this scale and level, to habitat disturbance. However, a large portion of variation in the fish assemblage was explainable by spatial and temporal variables. It is hypothesised that spatial-temporal structure at the landscape level may moderate local disturbance to habitat structure on contiguous reef.\ud \ud The second disturbance experiment was carried out on small patch reefs. To re-evaluate the current models of reef fish assemblage organisation, I implemented a factorial combination of direct (by fish removal) and indirect disturbance (by habitat alteration) and monitored the experiment over two years. Habitat disturbance generated strong, predictable changes in the fish assemblage which explained almost half the variation in the data set. In contrast, direct disturbance generated a lesser and shorter-term effect. The results from this experiment supported a model of reef fish assemblages as deterministic (within broad bounds), yet weakly interacting systems, the determinism of which was mediated by habitat.\ud \ud This study supports the initial premise that scaling rules for coral reef fish assemblages are mediated by habitat. As a consequence, habitat structure must be included into a general theory of coral reef fish ecology. An important precursor to the successful incorporation will be the parameterisation of the spatio-temporal dynamics of habitat structure, and the scales and forms of responses to habitat disturbance that fishes can be expected to make. Scale, far from being a black-box within which incongruous results are filed, can exert rational, mechanistic effects which can be incorporated both into the theoretical and empirical development of coral reef fish ecology

Satellite ocean data can inform precision fishing

Commercial fishing is important both economically and socially around the world. However, there is a need for fishing to become more efficient to maximise the protein caught to emissions released ratio. Predicting fish abundance and location using ocean predictors may enable greater fishing efficiency and precision. The recent release of catch data by the Norwegian Directorate of Fisheries stimulated the Nordic AI Meet to initiate a competition to apply artificial intelligence to increase commercial fishing efficiency. Satellite ocean model predictions and data were used to predict gross catches of ten commercial fish species landed in Norwegian ports, seven days into the future. Random forest regression ensembles generated monotonic linear predictions of actual catch. Predicting the exact location of maximum landings in the future week was elusive, however the predicted distribution maps provide skippers with an additional tool to supplement their knowledge and experience and enable more precise and efficient fishing

Community assembly of fish on small patch reefs: direct vs indirect disturbance

[Extract] Experimental studies of effects of disturbance on coral-reef fishes have generally been limited to direct disturbances - ie. defaunation (eg. Sale and Dybdahl 1975, 1978; Molles 1978). While natural occurrences of these types of disturbance have been recorded (Bohnsack 1983; Lassig 1983; Walsh 1983), most of the applications of defaunation have been used ostensibly to explore rules of community organization. Indirect disturbances, such as habitat alteration, have received far less experimental attention in tropical studies. Much of this disinterest in habitat disturbanee may be a result of the weakness of correlative evidence of fish-habitat association, especially at the patch-reef scale (Sale et al. 1994). In contrast, habitat manipulations have been widely and successfully applied to temperate reef fish assemblages and generally have demonstrated that habitat is an important structural element (Choat and Ayling 1987; Bodkin 1988; Jones 1984; DeMartini and Roberts 1990; Holbrook et al. 1990; Carr 1989, 1991; Syrns and Jones in prep.). In this study, we re-evaluate the importance of disturbance to fish assemblages on small patch reefs and compare the relative effects of direct vs. indirect disturbances

Soft corals exert no direct effects on coral reef fish assemblages

Correlations between abundance of organisms and their habitat have often been used as a measure of the importance of particular habitat features. However, experimental manipulation of the habitat provides a more unequivocal estimate of its importance. In this study we quantified how fish communities on small patch reefs covaried with changes in benthic cover habitat features. A random sample of small patch reefs was selected and both fish abundance and habitat measures recorded. Naturally occurring patch reefs could be classed into three habitat types based on their benthic cover. Reefs dominated by massive soft corals were the most abundant (50%), followed by those dominated by rock and soft corals in equal proportions (36%), then reefs dominated by branching corals (14%). Fish assemblages differed between the reef types. Communities on soft-coral-dominated and rock/soft-coral-dominated patch reefs formed a continuum of species responses correlated with degree of soft coral cover. In contrast, branching-coral-dominated reefs were occupied by a more discrete set of species. We tested the role of soft corals in contributing to this pattern by experimentally reducing soft coral cover on patch reefs from a baseline level of ~67% to ~33% and ~6%, and monitoring the experiment over 2 years. Contrary to expectations derived from the correlative data, and in contrast with previous manipulations of hard corals, soft-coral disturbance did not generate any corresponding changes in the fish assemblage. This "negative" result indicated that the quality and heterogeneity of habitat generated by soft corals on patch reefs was indistinguishable from equivalent-sized habitat patches formed by bare rock alone. Nevertheless, because soft corals are living organisms they have the potential to generate indirect effects by interacting with other organisms such as hard corals. In the long-term, we hypothesize that biotic interactions between habitat forming organisms might affect composition of fish assemblages on patch reefs

Habitat structure, disturbance and the composition of sand-dwelling goby assemblages in a coral reef lagoon

Coral reef lagoons and back reef areas are composed more of sand than hard reef habitat. They support a diverse mix of fishes, including species restricted to sandy habitats and those dependent on both hard and soft substrata. However the resident assemblages associated with sand and the factors affecting their distribution and abundance are poorly understood. Here we examine spatial co-variation in the abundance of burrowing goby assemblages and habitat characteristics in the lagoon at Lizard Island (Great Barrier Reef). The aim was to identify which key habitat-variables should be incorporated into models to predict the structure of sand-dwelling fish communities. We focused on 10 common sand goby species from 7 genera: Amblyeleotris, Cryptocentrus, Ctenogobiops and Vanderhorstia (associated with burrows constructed by alpheid shrimps), and Amblygobius, Oplopomus and Valenciennea (free-living, burrowing species). Spatial patterns were examined by stratifying the lagoon into 6 recognizable habitat zones, and conducting visual transects in replicate sites within each zone. The abundance of all goby species encountered and habitat variables (depth, distance from reef, topography, disturbance of different types, sediment composition) were recorded in each transect. Habitat characteristics and fish abundance, diversity and species composition differed markedly among habitat types and sites within habitats. There was a strong association between sites grouped according to habitat characteristics and goby assemblage. These changes reflected species-specific responses to different combinations of habitat variables and their interactions. All habitat variables measured were at least partially correlated, either positively or negatively, with the abundance of some of the species. Depth, distance from consolidated reef, sediment composition and the level of disturbance were particularly important. Our study indicates that sandy habitats, although superficially uniform, support highly structured fish communities influenced by a wide range of factors

Cytotoxic and anti-microbial activity of the sponge Iotrochota sp. as a function of size and spatial competitors

Secondary metabolites from marine invertebrates, such as sponges, have diverse ecological roles and may be used in anti-predation, anti-fouling and spatial competition. The thin encrusting sponge Iotrochota sp., found on the Great Barrier Reef, Australia, contains several novel indoles that may aid in spatial competition. To examine whether levels of surrounding competition affect the toxicity of Iotrochota sp., 24 sponges from Salamander Reef, Central Great Barrier Reef, subject to either high or low levels of surrounding competition, were sampled. Tissue samples were taken from areas where the sponge was in direct competition with neighbouring sessile invertebrates, as well as from areas where competition was less obvious. Compounds from the tissue samples were extracted and tested in both cytotoxicity and anti-microbial assays. However, neither cytotoxicity nor anti-microbial activity varied significantly between the high and low competition treatments. Cytotoxicity was greatest among large sponges, suggesting that size is an important factor contributing to the toxicity of Iotrochota sp. sponges in this study