Age at maturity of Mediterranean marine fishes

In this review we collected data on the age at maturity (tm) and maximum reported age (tmax) for 235 stocks of Mediterranean marine fishes, belonging to 82 species, 37 families, 12 orders and 2 classes (Actinopterygii and Elasmobranchii). Among Actinopterygii (mean tm ± SD = 2.20 ± 1.43 y, n = 215), tm ranged from 0.3 y, for the common goby Pomatoschistus microps, to 12 y, for dusky grouper Epinephelus marginatus, while among Elasmobranchii (mean tm ± SD = 5.94 ± 2.47 y, n = 20), tm ranged between 2.7 y, for brown ray Raja miraletus, and 12 y for picked dogfish Squalus acanthias. Overall, the tmax ranged between 1 y, for transparent goby Aphia minuta, and 70 y, for wreckfish Polyprion americanus. The mean tmax of Actinopterygii (tmax ± SD = 10.14 ± 9.42 y) was lower than that of Elasmobranchii (tmax ± SD = 14.05 ± 8.47 y). The tm exhibited a strong positive linear relation with tmax for both Actinopterygii (logtm = 0.58 ´ logtmax – 0.25, r2 = 0.51, P < 0.001) and Elasmobranchii (logtm = 0.67 ´ logtmax – 0.006, r2 = 0.51, P = 0.007). The mean tm/tmax did not differ significantly with sex within Actinopterygii (ANOVA: F = 0.27, P = 0.60, n = 90; females: mean ± SD = 0.276 ± 0.143; males: mean ± SD = 0.265 ± 0.138) and Elasmobranchii (ANOVA: F = 1.44, P = 0.25, n = 10; females: mean ± SD = 0.499 ± 0.166; males: mean ± SD = 0.418 ± 0.133). Finally, the dimensionless ratio tm/tmax was significantly lower (ANOVA: F = 31.04, P < 0.001) for Actinopterygii (mean ± SD = 0.270 ± 0.135, n = 180) than for Elasmobranchii, (mean ± SD = 0.458 ± 0.152, n = 20), when stocks with combined sexes were excluded from the analysis

What’s on the (publication fee) menu, who pays the bill and what should be the venue?

We address the cost of access to knowledge and its ethical implications in ‘true’, ‘pseudo’ and ‘hybrid’ OA journals

Editorial note on reproductive biology of fishes

Fish reproductive biology (onset and duration of spawning, sex ratio, maturity stages, length and age at maturity, and fecundity) is important in fisheries research, stock assessment, and management. In this editorial note, we provide some criteria and recommendations on issues of fish reproductive biology, which may be useful in research planning, data analysis and presentation, as well as in manuscript preparation

Editorial note on weight–length relations of fishes

Weight-length relations of fishes are useful for estimation of biomass from length observations, e.g., in fisheries or conservation research. Here we provide some guidance to authors of such papers, in order to facilitate the publication and review process

A Bayesian population model to estimate changes in the stock size in data poor cases using Mediterranean bogue (Boops boops) and picarel (Spicara smaris) as an example

The paper presents an effort to build a biologically realistic, age structured Bayesian model for the stock assessment of data poor fisheries where only aggregated catch data is available. The model is built using prior information from other areas and ecologically or taxonomically similar species. The modeling approach is tested with data poor fisheries on the Cyclades islands in Greek archipelago. The two most important species in the area are selected: bogue (Boops boops) and picarel (Spicara smaris). Both are hermaphroditic. The only data available is the total catch from 1950 to 2010. Information was gathered about natural mortality, recruitment, growth, body size, fecundity, and sex ratio. There were significant problems in finding reliable prior information and a uniform prior was used for fishing mortality. The models at their present stage are not used to give management advice. The biological characteristics of the species in that area should be further studied. However, the posteriors of biological parameters reflect the best available knowledge on these species and they could be used in future studies or in simpler biomass dynamics models as priors

Residual currents and fluxes through the mouth of Vassova coastal lagoon

An intensive sampling program of physical and chemical parameters at the mouth of Vassova lagoon (Northern Greece) during 4 separate tidal cycles is described. The study aims at understanding the tidal circulation and estimating the instantaneous and residual fluxes of water, salt and nutrients through the entrance canal of this micro-tidal lagoon. Results showed that tidal flood exceeded in duration tidal ebb, under spring and neap tidal conditions. Ebb tidal currents were recorded higher than flood currents, especially under neap tidal conditions. Unsteady flow characterized the temporal variation of longitudinal and lateral velocity, inducing a rightward deflection on flood or ebb flow. The intra-tidal variability of dissolved inorganic nitrogen showed seasonal dependence, with higher values during September, October and early March, and lower during the late March period. Residual current and flux analysis into a Eulerian and a mass transport Stokes drift mechanism illustrated that advective water and dissolved parameters (i.e., salt and nitrates, phosphates and chlorophyll-·) fluxes were an order of magnitude higher than tidal pumping effects. Water and dissolved constituents moved into the lagoon under neap tidal conditions and out of the lagoon during spring tidal conditions. Calculated flushing times ranged from 5 to 14 days, with neap tidal conditions and nearly zero freshwater discharge producing the longer flushing time. Lower water flushing effects were generated under spring tides and increased precipitation

Exploitation and status of European stocks

Report about the outcome of four workshops in 2016, about the assessment of all European stock

Spatial, Temporal, and Habitat-Related Variation in Abundance of Pelagic Fishes in the Gulf of Mexico: Potential Implications of the Deepwater Horizon Oil Spill

Time-series data collected over a four-year period were used to characterize patterns of abundance for pelagic fishes in the northern Gulf of Mexico (GoM) before (2007-2009) and after (2010) the Deepwater Horizon oil spill. Four numerically dominant pelagic species (blackfin tuna, blue marlin, dolphinfish, and sailfish) were included in our assessment, and larval density of each species was lower in 2010 than any of the three years prior to the oil spill, although larval abundance in 2010 was often statistically similar to other years surveyed. To assess potential overlap between suitable habitat of pelagic fish larvae and surface oil, generalized additive models (GAMs) were developed to evaluate the influence of ocean conditions on the abundance of larvae from 2007-2009. Explanatory variables from GAMs were then linked to environmental data from 2010 to predict the probability of occurrence for each species. The spatial extent of surface oil overlapped with early life habitat of each species, possibly indicating that the availability of high quality habitat was affected by the DH oil spill. Shifts in the distribution of spawning adults is another factor known to influence the abundance of larvae, and the spatial occurrence of a model pelagic predator (blue marlin) was characterized over the same four-year period using electronic tags. The spatial extent of oil coincided with areas used by adult blue marlin from 2007-2009, and the occurrence of blue marlin in areas impacted by the DH oil spill was lower in 2010 relative to pre-spill years

Research for PECH Committee - Discard ban, landing obligation and MSY in the Western Mediterranean Sea - the Spanish case

The demersal fisheries in the Mediterranean Sea are heavily overfished but the landing obligation will not help to reach MSY because it will not decrease fishing mortality. The new proposal of the Commission introduces total allowable effort as a new way to regulate Western Mediterranean demersal fisheries by significantly reducing fishing time. However, this new management measure must be complemented with increased gear selectivity, implementation of closed areas and local co-management plans. Different approaches to reduce fishing mortality may have different socio-economic impact

Climate impact on Italian fisheries (Mediterranean Sea)

Global warming is increasingly affecting marine ecosystems and ecological services they provide. One of the major consequences is a shift in species geographical distribution, which may affect resources availability to fisheries. We computed the mean temperature of the catch (MTC) for Italian catches from 1972 to 2012 to test if an increase of warmer-water species against colder-water ones was observed. We further analysed the relationship among MTC, landings, fishing effort and climatic factors through a Linear Mixed Models approach. Global MTC increased at a rate of 0.12 _C per decade. Though, by considering the influence of sea surface temperature (SST), a strongest increase (0.31 _C) was estimated in southernmost areas, while in the northernmost basin (Northern Adriatic Sea) a decrease of 0.14 _C was observed. SST resulted the most relevant driver, and the relationship between MTC and SST showed a high spatial variability both in terms of strength and sign, being positively stronger in southernmost areas while negative in the northernmost basin. The result is probably underestimated since several psychrophilous and thermophilous species were not included in the analysis. However, it seems that a change towards warmer-water species has already occurred in Italian marine ecosystems. Conversely, total landings temporal dynamics seem mostly driven by changes in fishing effort rather than by MTC and climatic factors. Consequently, fishery management strategies need to focalize primarily on fishing effort reduction, in order to reduce the pressure on the stocks while increasing their resilience to other stressors, among which global warmingGlobal warming is increasingly affecting marine ecosystems and ecological services they provide. One of the major consequences is a shift in species geographical distribution, which may affect resources availability to fisheries. We computed the mean temperature of the catch (MTC) for Italian catches from 1972 to 2012 to test if an increase of warmer-water species against colder-water ones was observed. We further analysed the relationship among MTC, landings, fishing effort and climatic factors through a Linear Mixed Models approach. Global MTC increased at a rate of 0.12 A degrees C per decade. Though, by considering the influence of sea surface temperature (SST), a strongest increase (0.31 A degrees C) was estimated in southernmost areas, while in the northernmost basin (Northern Adriatic Sea) a decrease of 0.14 A degrees C was observed. SST resulted the most relevant driver, and the relationship between MTC and SST showed a high spatial variability both in terms of strength and sign, being positively stronger in southernmost areas while negative in the northernmost basin. The result is probably underestimated since several psychrophilous and thermophilous species were not included in the analysis. However, it seems that a change towards warmer-water species has already occurred in Italian marine ecosystems. Conversely, total landings temporal dynamics seem mostly driven by changes in fishing effort rather than by MTC and climatic factors. Consequently, fishery management strategies need to focalize primarily on fishing effort reduction, in order to reduce the pressure on the stocks while increasing their resilience to other stressors, among which global warming