Conservation benefits of temperate marine protected areas: variation among fish species

The positive impact of conservation action

Governments recently adopted new global targets to halt and reverse the loss of biodiversity. It is therefore crucial to understand the outcomes of conservation actions. We conducted a global meta-analysis of 186 studies (including 665 trials) that measured biodiversity over time and compared outcomes under conservation action with a suitable counterfactual of no action. We find that in two-thirds of cases, conservation either improved the state of biodiversity or at least slowed declines. Specifically, we find that interventions targeted at species and ecosystems, such as invasive species control, habitat loss reduction and restoration, protected areas, and sustainable management, are highly effective and have large effect sizes. This provides the strongest evidence to date that conservation actions are successful but require transformational scaling up to meet global targets.

Environmental Drivers and Social Structure Features behind the Low Reproductive Success of Dusky Groupers Epinephelus marginatus (Lowe, 1834) in a Mediterranean Marine Protected Area

Marine protected areas (MPAs) are considered key tools for achieving the sustainability of coastal fisheries by allowing habitat and species conservation by means of use regulations and active management. The effects of protection are more visible in slow-growing, high site fidelity and late-maturing species such as dusky grouper, a flagship species for all the fishermen and divers in the Mediterranean Sea. We studied the reproductive behavior of dusky grouper at Tabarca Island Marine Protected Area (TIMPA) in order to: (a) describe its temporal pattern; (b) evaluate the relationships among reproductive behavior and environmental factors and (c) verify the effects of social structure on reproductive activity. We observed all the behavior patterns previously reported in other studies besides the final spawn event. Our results evidenced that the monthly average density of dusky groupers tended to increase when temperature rose close to the seabed and without defined temporal limits for reproductive behavior. Among the environmental factors considered, visibility exhibited a very strong effect on the reproductive behavior of dusky grouper, interacting significantly with seabed temperature and thermocline. Regarding the effects of social structure, reproductive activity was positively correlated with the presence of large-sized individuals. We have discussed the differential facts of the reproductive activity of dusky groupers observed at TIMPA relating the results to the biogeographical location, the patterns of the environmental drivers (such as the seabed temperature per day, the thermocline, the visibility, the stream force, the photoperiod and the divers per day) and the structure of the habitat. These negative results contrast with the existing knowledge and generate new working hypotheses useful to improve the efficiency of MPAs and the sustainability of coastal fisheries.

On the spillover effect and optimal size of marine reserves for sustainable fishing yields

Marine reserves are an essential component of modern fishery management. Marine reserves, which represent a management tradeoff between harvesting and conservation, are fundamental to maintenance of fisheries. Finding optimal reserve sizes that improve fishing yields is not only of theoretical interest, but also of practical importance to facilitate decision making. Also, since the migratory behavior of some species influences the spillover effect of a marine reserve, this is a key consideration when assessing performance of marine reserves. The relationship between optimal reserve size and migration rate/mode has not been well studied, but it is fundamental to management success. Here, I investigate optimal reserve size and its management outcome with different levels of spillover via a simple two-patch mathematical model. In this model, one patch is open to fishing, and the other is closed. The two-patch model is aggregated by single-population dynamics when the migration rate is sufficiently larger than the growth rate of a target species. At this limit, I show that an optimal reserve size exists when pre-reserve fishing occurs at fishing mortality larger than f_MSY, the fishing mortality at the maximum sustainable yield (MSY). Also, the fishing yield at an optimal reserve size becomes as large as MSY at the limit. Numerical simulations at various migration rates between the two patches suggest that the maximum harvest under management with a marine reserve is achieved at this limit. This contrasts with the conservation benefit which is maximized at an intermediate migration rate. Numerical simulations show that the above-mentioned condition for an optimal reserve size to exist derived from the aggregated model is necessary when the migration rate is not sufficiently large, and that a moderate migration rate is further necessary for an optimal reserve size to exist. However, high fishing mortality reduces this requirement.

Ecological responses to blue water MPAs

Marine protected areas (MPAs) can contribute to protecting biodiversity and managing ocean activities, including fishing. There is, however, limited evidence of ecological responses to blue water MPAs. We conducted the first comprehensive evaluation of impacts on fisheries production and ecological responses to pelagic MPAs of the Pacific Remote Islands Marine National Monument. A Bayesian time series-based counterfactual modelling approach using fishery-dependent data was used to compare the temporal response in the MPAs to three reference regions for standardized catch rates, lengths, trophic level of the catch and species diversity. Catch rates of bigeye tuna, the main target species (Kingman/Palmyra MPA, causal effect probability >99% of an 84% reduction; 95% credible interval: -143%, -25%), and blue shark (Johnston MPAs, causal effect probability >95%) were significantly lower and longnose lancetfish significantly higher (Johnston MPAs, causal effect probability >95%) than predicted had the MPAs not been established, possibly from closing areas near shallow features, which aggregate pelagic predators, and from ‘fishing-the-line’. There were no apparent causal impacts of the MPAs on species diversity, lengths and trophic level of the catch, perhaps because the MPAs were young, were too small, did not contain critical habitat for specific life-history stages, had been lightly exploited or experienced fishing-the-line. We also assessed model-standardized catch rates for species of conservation concern and mean trophic level of the catch within and outside of MPAs. Displaced effort produced multi-species conflicts: MPAs protect bycatch hotspots and hotspots of bycatch-to-target catch ratios for some at-risk species, but coldspots for others. Mean trophic level of the catch was significantly higher around MPAs, likely due to the aggregating effect of the shallow features and there having been light fishing pressure within MPAs. These findings demonstrate how exploring a wide range of ecological responses supports evidence-based evaluations of blue water MPAs.

Preference classes in society for coastal marine protected areas

Marine protected areas (MPAs) are increasingly being used as conservation tools in the marine environment. Success of MPAs depends upon sound scientific design and societal support. Studies that have assessed societal preferences for temperate MPAs have generally done it without considering the existence of discrete groups of opinion within society and have largely considered offshore and deep-sea areas. This study quantifies societal preferences and economic support for coastal MPAs in Wales (UK) and assesses the presence of distinct groups of preference for MPA management, through a latent class choice experiment approach. Results show a general support for the protection of the marine environment in the form of MPAs and that society is willing to bear the costs derived from conservation. Despite a general opposition toward MPAs where human activities are completely excluded, there is some indication that three classes of preferences within society can be established regarding the management of potentially sea-floor damaging activities. This type of approach allows for the distinction between those respondents with positive preferences for particular types of management from those who experience disutility. We conclude that insights from these types of analyses can be used by policy-makers to identify those MPA designs and management combinations most likely to be supported by particular sectors of society.

Chondrichthyan research in South America: Endocrinology overview and research trends over 50 years (1967-2016) compared to the rest of the world

The endocrine system plays a crucial role in regulating the activity of cells and organs among vertebrates, including the class Chondrichthyes. Accordingly, Chondrichthyan endocrinology publications have been steadily increasing in the global literature. However, while interest in South American Chondrichthyan research has been growing over the last 50 years, the field of endocrinology related to Chondrichthyans has been limited. Understanding the trajectory of a scientific discipline assists researchers and stakeholders in making decisions regarding which research areas require further attention. Further, visualisation techniques based on bibliometric analysis of scientific publications assist in understanding fluctuations in the trends of specific research fields over time. In this study, Chondrichthyan research publications over time were analysed by creating visualisation maps using VOSviewer bibliometric software. Trends in South America Chondrichthyan research with an emphasis on endocrinology were explored over a 50-year period (1967-2016). These trends were compared with Chondrichthyans research worldwide for the more recent 15-year period (2002-2016). The number of South America Chondrichthyan scientific publications increased from six during the 1967-1981 period to 112 in 2016. However, only eight papers were found published in the area of Chondrichthyan endocrinology research. Fisheries, reproduction and taxonomy were the dominate research areas in South America over the 50 years. For the more recent 15 years, South American publications comprised 11% of the total literature published globally. While South America research outputs fluctuated closely with global research trends, differences appeared when comparing areas of growth. This study describes the trends in Chondrichthyan research literature globally and more specifically in South America. Although South American countries may never contribute to the same scale as the wider international scientific community, the future of Chondrichthyans would strongly benefit from the contributions of the many diverse research groups around the world.

Soft-bottom fishes and spatial protection: findings from a temperate marine protected area

Numerous studies over the last decades have focused on marine protected areas (MPAs) and their effects on fish communities. However, there is a knowledge gap regarding how species that live associated with soft-substrates (e.g., sand, mud) respond to spatial protection. We analyzed abundance, biomass and total lengths of the soft-bottom fishes in a multiple-use MPA in the north-eastern Atlantic, the Luiz Saldanha Marine Park (Portugal), during and after the implementation of its management plan. Data were collected by experimental fishing in areas with three different levels of protection, during the implementation period and for three years after full implementation of the MPA. Univariate analysis detected significant biomass increases between the two periods. Fish assemblages were mainly structured by depth and substrate, followed by protection level. Community composition analyses revealed significant differences between protection levels and between the two periods. Species exhibited a broad variation in their response to protection, and we hypothesize that factors such as species habitat preferences, body size and late maturity might be underlying determinants. Overall, this study provides some evidence of protection effectiveness in soft-bottom fish communities, supported by the significant increase in biomass in the protected areas and the positive trends of some species.

Using marine reserves to manage impact of bottom trawl fisheries requires consideration of benthic food-web interactions

Marine protected areas (MPAs) are widely used to protect exploited fish species as well as to conserve marine habitats and their biodiversity. They have also become a popular management tool for bottom trawl fisheries, a common fishing technique on continental shelves worldwide. The effects of bottom trawling go far beyond the impact on target species, as trawls also affect other components of the benthic ecosystem and the seabed itself. This means that for bottom trawl fisheries, MPAs can potentially be used not only to conserve target species but also to reduce impact of these side effects of the fishery. However, predicting the protective effects of MPAs is complicated because the side effects of trawling potentially alter the food-web interactions between target and non-target species. These changes in predatory and competitive interactions among fish and benthic invertebrates may have important ramifications for MPAs as tools to manage or mitigate the effects of bottom trawling. Yet, in current theory regarding the functioning of MPAs in relation to bottom trawl fisheries, such predatory and competitive interactions between species are generally not taken into account. In this study, we discuss how food-web interactions that are potentially affected by bottom trawling may alter the effectiveness of MPAs to protect (1) biodiversity and marine habitats, (2) fish populations, (3) fisheries yield, and (4) trophic structure of the community. We make the case that in order to be applicable for bottom trawl fisheries, guidelines for the implementation of MPAs must consider their potential food-web effects, at the risk of failing management.

Habitat and ecology of Nephrops norvegicus

This review summarizes the data on habitat, population ecology and ecosystem roles of Nephrops norvegicus. The species has a broad range in the northeast Atlantic and Mediterranean, although it is possible that small or isolated patches of suitable habitat may not be occupied due to restrictions on larval supply. Nephrops densities are related to the silt-clay content of sediments, with interactions between habitat quality and density indicating competition for resources. An analysis of density-size interactions across fishery functional management units (FUs) suggests that growth is suppressed at high densities due to competition (e.g. in the western Irish Sea), although recruitment dynamics or size-selective mortality may also shape the size structure of populations. Nephrops biomass available across FUs may be similar, reflecting a constant yield due to the inverse relationship between individual size and population density. Gaps in the understanding of Nephrops' ecology reflect uncertain ageing criteria, reliance on fisheries-dependent data and few if any undisturbed habitats in which to examine fisheries-independent interactions.

Spatial heterogeneity in fishing creates de facto refugia for endangered Celtic Sea elasmobranchs

The life history characteristics of some elasmobranchs make them particularly vulnerable to fishing mortality; about a third of all species are listed by the IUCN as Threatened or Near Threatened. Marine Protected Areas (MPAs) have been suggested as a tool for conservation of elasmobranchs, but they are likely to be effective only if such populations respond to fishing impacts at spatial-scales corresponding to MPA size. Using the example of the Celtic Sea, we modelled elasmobranch biomass (kg h(-1)) in fisheries-independent survey hauls as a function of environmental variables and 'local' (within 20 km radius) fishing effort (h y(-1)) recorded from Vessel Monitoring Systems data. Model selection using AIC suggested strongest support for linear mixed effects models in which the variables (i) fishing effort, (ii) geographic location and (iii) demersal fish assemblage had approximately equal importance in explaining elasmobranch biomass. In the eastern Celtic Sea, sampling sites that occurred in the lowest 10% of the observed fishing effort range recorded 10 species of elasmobranch including the critically endangered Dipturus spp. The most intensely fished 10% of sites had only three elasmobranch species, with two IUCN listed as Least Concern. Our results suggest that stable spatial heterogeneity in fishing effort creates de facto refugia for elasmobranchs in the Celtic Sea. However, changes in the present fisheries management regime could impair the refuge effect by changing fisher's behaviour and displacing effort into these areas.

Movement patterns of the draughtboard shark Cephaloscyllium laticeps (Scyliorhinidae) determined by passive tracking and conventional tagging

A combination of passive tracking and conventional tagging was used to provide insight into the movement patterns of the draughtboard shark Cephaloscyllium laticeps, the most common catshark in coastal areas of southern Australia. A series of acoustic receivers deployed throughout south-eastern Tasmania as well as a receiver array along an isolated reef, Crayfish Point Reserve (CPR), passively tracked 25 C. laticeps from January to July 2003. Cephaloscyllium laticeps were present from 4 to 98 days. The majority of the C. laticeps stayed within the CPR where most individuals were active throughout the night. They were found actively moving (i.e. when a C. laticeps was consecutively detected by two or more non-overlapping receivers, suggesting the individual was moving) and spending periods of minor movements (i.e. when an individual was consecutively detected by only one receiver, suggesting it was at rest). The length of these minor movements periods, observed both day and night, ranged from 1 h to 5 days. In addition to passive tracking, 1552 conventionally tagged C. laticeps were released in the eastern and south-western coastal areas of Tasmania and within the CPR between January 2000 and April 2007. The CPR showed a higher recapture rate, 38%, than eastern and south-western areas where the recapture rates were 10 and 3%, respectively. Within the CPR, 36% of the sharks were recaptured on multiple occasions. The maximum time at liberty ranged from 1 month to 7 years. The majority of the C. laticeps were recaptured in the vicinity of where they were released (<10 km), although larger longer-term movements of up to 300 km were recorded. The large amount of multiple recaptures within the CPR, in addition to acoustic tagging results, indicated a high degree of site fidelity for C. laticeps. This isolated reef appears to be an important habitat for this species, and therefore, the current protection status of this area is probably beneficial for the conservation of C. laticeps.

An unintended experiment in fisheries science: a marine area protected by war results in Mexican waves in fish numbers-at-age

Marine protected areas (MPAs) are attaining increasing importance in the management of marine ecosystems. They are effective for conservation in tropical and subtropical areas (mainly coral and rocky reefs), but it is debated whether they are useful in the management of migratory fish stocks in open temperate regions. World War II created a large marine area within which commercial fishing was prevented for 6 years. Here we analyse scientific trawl data for three important North Sea gadoids, collected between 1928 and 1958. Using statistical models to summarise the data, we demonstrate the potential of MPAs for expediting the recovery of over-exploited fisheries in open temperate regions. Our age-structured data and population models suggest that wild fish stocks will respond rapidly and positively to reductions in harvesting rates and that the numbers of older fish in a population will react before, and in much greater proportion, than their younger counterparts in a kind of Mexican wave. Our analyses demonstrate both the overall increase in survival due to the lack of harvesting in the War and the form of the age-dependent wave in numbers. We conclude that large closed areas can be very useful in the conservation of migratory species from temperate areas and that older fish benefit fastest and in greater proportion. Importantly, any rise in spawning stock biomass may also not immediately result in better recruitment, which can respond more slowly and hence take longer to contribute to higher future harvestable biomass levels.

Marine reserves: fish life history and ecological traits matter

Marine reserves are assumed to protect a wide range of species from deleterious effects stemming from exploitation. However, some species, due to their ecological characteristics, may not respond positively to protection. Very little is known about the effects of life history and ecological traits (e.g., mobility, growth, and habitat) on responses of fish species to marine reserves. Using 40 data sets from 12 European marine reserves, we show that there is significant variation in the response of different species of fish to protection and that this heterogeneity can be explained, in part, by differences in their traits. Densities of targeted size-classes of commercial species were greater in protected than unprotected areas. This effect of protection increased as the maximum body size of the targeted species increased, and it was greater for species that were not obligate schoolers. However, contrary to previous theoretical findings, even mobile species with wide home ranges benefited from protection: the effect of protection was at least as strong for mobile species as it was for sedentary ones. Noncommercial bycatch and unexploited species rarely responded to protection, and when they did (in the case of unexploited bentho-pelagic species), they exhibited the opposite response: their densities were lower inside reserves. The use of marine reserves for marine conservation and fisheries management implies that they should ensure protection for a wide range of species with different life-history and ecological traits. Our results suggest this is not the case, and instead that effects vary with economic value, body size, habitat, depth range, and schooling behavior.

Placing marine protected areas onto the ecosystem-based management seascape

The rapid increase in the science and implementation of marine protected areas (MPAs) around the world in the past 15 years is now being followed by similar increases in the science and application of marine ecosystem-based management (EBM). Despite important overlaps and some common goals, these two approaches have remained either separated in the literature and in conservation and management efforts or treated as if they are one and the same. In the cases when connections are acknowledged, there is often little assessment of if or how well MPAs can achieve specific EBM goals. Here we start by critically evaluating commonalities and differences between MPAs and EBM. Next, we use global analyses to show where and how much no-take marine reserves can be expected to contribute to EBM goals, specifically by reducing the cumulative impacts of stressors on ocean ecosystems. These analyses revealed large stretches of coastal oceans where reserves can play a major role in reducing cumulative impacts and thus improving overall ocean condition, at the same time highlighting the limitations of marine reserves as a single tool to achieve comprehensive EBM. Ultimately, better synergies between these two burgeoning approaches provide opportunities to greatly benefit ocean health.