Density dependence in marine protected populations: a review

The cessation or reduction of fishing in marine protected areas (MPAs) should promote an increase in abundance and mean size and age of previously exploited populations. Thus density-dependent changes in life-history characteristics should occur when populations are allowed to recover in MPAs. In this review, we synthesize the existing information on resource limitation in marine ecosystems, density-dependent changes in life-history traits of exploited populations and evidence for biomass export from MPAs. Most evidence for compensatory changes in biological variables has been derived from observations on populations depleted by high fishing mortality or on strong year classes, but these changes are more evident in juveniles than in adults and in freshwater rather than in marine systems. It is unclear if adults of exploited marine populations are resource limited. This may suggest that exploited populations are controlled mainly by density-independent processes, which could be a consequence of the depleted state of most exploited populations. MPAs could be a useful tool for testing these hypotheses. If we assume that resources become limiting inside MPAs, it is plausible that, if suitable habitats exist, mobile species will search for resources outside of the MPAs, leading to export of biomass to areas which are fished. However, it is not possible to establish from the available data whether this export will be a response to resource limitation inside the MPAs, the result of random movements across MPA boundaries or both. We discuss the implications of this process for the use of MPAs as fisheries management tools.Financial support was provided by the EU CEC DGXII – MAST III contract number: MAS3-ct97-0155

Conserving European biodiversity across realms

Terrestrial, freshwater, and marine ecosystems are connected via multiple biophysical and ecological processes. Identifying and quantifying links among ecosystems is necessary for the uptake of integrated conservation actions across realms. Such actions are particularly important for species using habitats in more than one realm during their daily or life cycle. We reviewed information on the habitats of 2,408 species of European conservation concern and found that 30% of the species use habitats in multiple realms. Transportation and service corridors, which fragment species habitats, were identified as the most important threat impacting ∼70% of the species. We examined information on 1,567 European Union (EU) conservation projects funded over the past 25 years, to assess the adequacy of efforts toward the conservation of “multi‐realm” species at a continental scale. We discovered that less than a third of multi‐realm species benefited from projects that included conservation actions across multiple realms. To achieve the EU's conservation target of halting biodiversity loss by 2020 and effectively protect multi‐realm species, integrated conservation efforts across realms should be reinforced by: (1) recognizing the need for integrated management at a policy level, (2) revising conservation funding priorities across realms, and (3) implementing integrated land‐freshwater‐sea conservation planning and management

North East Atlantic vs. Mediterranean Marine Protected Areas as Fisheries Management Tool

The effectiveness of management initiatives implemented in the context of the European Common Fisheries Policy has been questioned, especially with regard to the Mediterranean. Some of the analyses made to compare the fishing activity and management measures carried out in the North East Atlantic and in the Mediterranean do not take into account some of the differentiating peculiarities of each of these regions. At the same time, they resort to traditional fisheries management measures and do not discuss the role of marine protected areas as a complementary management tool. In this respect, the apparent failure of marine protected areas in the North-East Atlantic compared with the same in the Mediterranean is challenging European fishery scientists. Application of the classical holistic view of ecological succession to the functioning of fishery closures and no-use areas highlights the importance of combining both management regimes to fully satisfy both fishery- and biodiversity-oriented goals. We advocate that an optimal management strategy for designing an MPA to protect biodiversity and sustain fishing yields consists of combining a network of no-use areas (close to their mature state) with fish boxes (buffer zones maintained by fishing disturbance in a relatively early successional stage, where productivity is higher), under a multi-zoning scheme. In this framework, the importance of no-use areas for fisheries is based on several observations: (1) They preserve biological diversity at regional scale, at all levels—specific, habitat/seascape, and also genetic diversity and the structure of populations, allowing natural selection to operate. (2) They permit the natural variability of the system to be differentiated from the effects of regulation and to be integrated in appropriate sampling schemes as controls. (3) They maintain the natural size and age structure of the populations, hence maximizing potential fecundity, allowing biomass export to occur from core to regulated areas, dampening the fluctuations derived from deviations from the theoretical optimal effort in the fishing zone

la Reserva Marina de Cabo de Palos - Islas Hormigas

Los autores pertenecen a la Universidad de Murcia, Instituto Español de Oceanografía, Museo Nacional de Ciencias Naturales y a la Asociación de Naturalistas del Sureste (ANSE). FOTOGRAFÍA: Javier Ferrer y Javier Murcia ILUSTRACIÓN: Alberto Molina Enlace de la retransmisión de la actividad: https://www.youtube.com/live/1q2mxYz4Wy0?feature=shareSe trata de una guía que nos ofrece una completa visión de la riqueza biológica de esta reserva marina, sus características geológicas y oceanográficas, la pesca artesanal, su gestión, el buceo, así como los cambios observados en las últimas décadas. Todo ello apoyado por una amplia documentación fotográfica e ilustraciones de los distintos ecosistemas.N

The "Tracked Roaming Transect" and distance sampling methods increase the efficiency of underwater visual censuses.

Underwater visual census (UVC) is the most common approach for estimating diversity, abundance and size of reef fishes in shallow and clear waters. Abundance estimation through UVC is particularly problematic in species occurring at low densities and/or highly aggregated because of their high variability at both spatial and temporal scales. The statistical power of experiments involving UVC techniques may be increased by augmenting the number of replicates or the area surveyed. In this work we present and test the efficiency of an UVC method based on diver towed GPS, the Tracked Roaming Transect (TRT), designed to maximize transect length (and thus the surveyed area) with respect to diving time invested in monitoring, as compared to Conventional Strip Transects (CST). Additionally, we analyze the effect of increasing transect width and length on the precision of density estimates by comparing TRT vs. CST methods using different fixed widths of 6 and 20 m (FW3 and FW10, respectively) and the Distance Sampling (DS) method, in which perpendicular distance of each fish or group of fishes to the transect line is estimated by divers up to 20 m from the transect line. The TRT was 74% more time and cost efficient than the CST (all transect widths considered together) and, for a given time, the use of TRT and/or increasing the transect width increased the precision of density estimates. In addition, since with the DS method distances of fishes to the transect line have to be estimated, and not measured directly as in terrestrial environments, errors in estimations of perpendicular distances can seriously affect DS density estimations. To assess the occurrence of distance estimation errors and their dependence on the observer's experience, a field experiment using wooden fish models was performed. We tested the precision and accuracy of density estimators based on fixed widths and the DS method. The accuracy of the estimates was measured comparing the actual total abundance with those estimated by divers using FW3, FW10, and DS estimators. Density estimates differed by 13% (range 0.1-31%) from the actual values (average = 13.09%; median = 14.16%). Based on our results we encourage the use of the Tracked Roaming Transect with Distance Sampling (TRT+DS) method for improving density estimates of species occurring at low densities and/or highly aggregated, as well as for exploratory rapid-assessment surveys in which divers could gather spatial ecological and ecosystem information on large areas during UVC

Metal concentration assessment using blood samples of two top predator fish species: Cabo de Palos - Islas Hormigas Marine Protected Area, Spain

VI Congreso Ibérico de Ictiología - VI Iberian Congress of Ichthyology (SIBIC2016), celebrado del 21 al 24 de junio de 2016 en Murcia.-- 1 pageEffects of metal accumulation in the marine biota are of great concern due to their possible effects on ecosystem function and productivity. Species of high trophic levels provide integrated information about bioaccumulation trends within their distribution range. Nevertheless, two factors constrain their current use as bioindicators of metal contamination: i) the difficulty of getting samples without sacrificing the organism, and ii) the lack of knowledge about how factors derived from fish behavior (e.g. feeding or usual distribution in the water column) may contribute to bioaccumulation. Here, we assessed the use of blood samples as a biomonitoring tool of metal contamination in two top predator fish species (Epinephelus costae and Epinephelus marginatus). For this aim, we studied the relationship among metals concentrations of Fe, Cu, Hg, Pb, Zn, Se, Cd and As, as well as their levels among species and by size through analyzing blood samples following ICP-MS technique. Detectable concentrations of Cd were not found for any of the species. Significant Zn/As, As/Se and Pb/As correlations were found for E. costae, while for E. marginatus only Cu/Pb and Zn/Se were related. A strong positive relationship between mercury concentration and size was found in both species, while zinc and cooper levels were positive related to size only in E. marginatus. Selenium differed significantly between species, with higher concentrations in E. costae. Mercury concentrations found require further research in edible tissues (e.g. muscle) since there is no regulation establishing thresholds for mercury concentrations in blood. According to our results, the use of blood as a monitoring tool for metal contamination could be posed as an alternative to other techniques which need the sacrifice of the individuals, especially for those species that are in a critical state of conservation at local or/and global scalePeer Reviewe

Density estimations (D) (fish/300m²) and coefficients of variations (CV) for studied species and the total of groupers for different combinations of transects types and census widths in Cabo de Palos and Cabo Tiñoso.

<p>Note that CST values in Cabo Tiñoso were derived from simulations. CST = Conventional Strip Transect. TRT = Tracked Roaming Transect. FW3 and FW10 = Fixed Width of 3 and 10 m for each side of the transects, respectively. DS = Distance Sampling Method. The census area of each survey is detailed in m² considering total transect lengths and 6 and 20 m width for FW´s estimators and 40 m width for the DS estimator.</p

Number (N) of wooden fishes estimated with the Distance Sampling (DS) method by the experienced and non-experienced divers for the total census area (3000 m²) and the confidence interval (N CI 95%) at p < 0.05.

<p>DS estimator: the best fit from the nine estimators tested with the DISTANCE software. D = Density per 300 m2. %CV = Coefficient of variation of the estimation in percentage. N detected (%) = Number of wooden fishes detected by divers and the percentage of the total wooden fish. MDD = Mean distance detection derived from visual estimations and standard deviation (SD) by divers. "*" Actual number of wooden fishes. "**" Actual mean distance.</p

Study sites.

<p>(A) Islas Hormigas and Hormigon in Cabo de Palos Marine Reserve (37.6550° N -0.6497° E). The distance between islands is not to scale to ease the representation. (B) Cabo Tiñoso (37.5370° N -1.1419° E). Straight lines: 50-m Conventional Strip Transects. Curved lines: Tracks of the Tracked Roaming Transects.</p

Scheme of the count method using the Distance Sampling method.

<p>IL = imaginary line. X^1-2 = perpendicular distances of solitary individuals to the transect line. X³ = perpendicular distance of a school of fishes to the perpendicular line. The equipment (Fig 2) is illustrated above divers, like at the surface. Inset: The Tracked Roaming Transect equipment. A = Waterproof case for GPS. B = Body Board Slate. C = Diving reel. D = Weight.</p