Morphometric differentiation in small juveniles of the pink spotted shrimp (Farfantepenaeus brasiliensis) and the southern pink shrimp (F. notialis) in the Yucatan Peninsula, Mexico

The morphometric and morphological characters of the rostrum have been widely used to identify penaeid shrimp species (Heales et al., 1985; Dall et al., 1990; Pendrey et al., 1999). In this setting, one of the constraints in studies of penaeid shrimp populations has been the uncertainty in the identification of early life history stages, especially in coastal nursery habitats, where recruits and juveniles dominate the population (Dall et al., 1990; Pérez-Castañeda and Defeo, 2001). In the western Atlantic Ocean, Pérez-Farfante (1969, 1970, 1971a) described diagnostic characters of the genus Farfantepenaeus that allowed identification of individuals in the range of 8−20 mm CL (carapace length) on the basis of the following morphological features: 1) changes in the structure of the petasma and thelycum; 2) absence or presence of distomarginal spines in the ventral costa of the petasma; 3) the ratio between the keel height and the sulcus width of the sixth abdominal somite; 4) the shape and position of the rostrum with respect to the segments and flagellum of the antennule; and 5) the ratio between rostrum length (RL) and carapace length (RL/CL). In addition, she classified Farfantepenaeus into two groups according to the shape and position of the rostrum with respect to the segments and flagellum of the antennule and the ratio RL/CL: 1) F. duorarum and F. notialis: short rostrum, straight distally, and the proximodorsal margin convex, usually extending anteriorly to the end of distal antennular segment, sometimes reaching to proximal one-fourth of broadened portion of lateral antennular flagellum, with RL/CL 0.80. Pérez-Farfante stressed that, for the recognition to species level of juveniles <10 mm CL, all the characters listed above should be considered because occasionally one alone may not prove to be diagnostic. However, the only characters that could be distinguished for small juveniles in the range 4−8 mm CL are those defined on the rostrum. Therefore, it has been almost impossible to identify and separate small specimens of Farfantepenaeus (Pérez-Farfante, 1970, 1971a; Pérez-Farfante and Kensley, 1997)

Experimental management of an exploited sandy beach bivalve population

ABSTRACT Variation in physical factors is considered the primary organizational force regulating macrobenthic populations and communities of exposed sandy beaches. However, there has been no quantitative evaluation of the intensity of human predation on the macrofauna inhabiting these systems, and information on biological interactions is also lacking. In the present study I review the results of a long-term monitoring study on the yellow clam Mesodesma mactroides (Deshayes, 1854) (Bivalvia: Mesodesmatidae) of an Uruguayan exposed sandy beach, including the effect of a human exclusion experiment as a way to acquire knowledge about its population structure and dynamics. Experimental management was based on the closure of the fishery for 32 months, in which a great part of the artisanal fishery community and the coastal marine authorities were involved in control operations. The experiment was a useful approach to testing the effect of fishing disturbing or altering the yellow clam population: the wide range of fishing effort levels through time allowed the detection of some patterns and processes that until the closure were unknown, namely: (I) the stock recruitment-relationship showed overcompensation, i.e. the inhibition of recruitment at highest adult densities: (2) growth rates of the newly settled cohorts were inversely correlated with the corresponding average adult density: (3) post-settlement natural mortality was htghest in the densest cohorts, and was also a function of fishing activity: (4) the amount of fishing effort exerted over Mesodesma mact ides explained variations in abundance of the sympatric population of the wedge clam Donax hanleya s Philippi, 1845 (Bivalvia: Donacidae). It is concluded that experimental management is a powerful approach to identify factors governing the dynamics of exploited sandy beach populations, to acquire the basic biological knowledge needed to perform adequate management strategies and to quantify the effect of harvesting on other components of the macrofauna. It is also stressed that further research in sandy beach populations should include human activities as important factors affecting long-term trends. Key words: Mesodesma population dynamics, fishing, long-term. RESUMEN Las playas de arena expuestas constituyen ambientes marinos rigurosos, en Ios cuales variaciones en Ios factores ffsicos son considerados como reguladores de la abundancia de poblaciones y comunidades macrobentonicas. Sin embargo, no existe una evaluaci n cuantitativa de la intensidad del impacto humano (pesca) en la macrofauna que habita esos sistemas. y la informaci n referida a interacciones biologicas es fragmentaria o inexistente. En este trabajo presento una revision de Ios resultados sobre un estudio de largo plazo de la almeja amarilla Mesodesma (Deshayes, 1854) (Bivalvia: Mesodesmatidae) de la costa atl ntica uruguaya, incluyendo el efecto de un experimento de exclusion humana (clausura de la pesquerfa) como una alternativa para adquirir conocimientos basicos sobre la dinamica de la poblacion. El manejo experimental estuvo basado en la clausura de la pesqueria por 32 meses. en Ios cuales la autoridad maritima y la comunidad pesquera artesanal participaron en el control de la medida. El cxpcrimento fue una poderosa herramienta para evaluar el efecto de la pesca como agente de disturbio de la poblacion de almeja amarilla: Ios contrastantes niveles de esfuerzo pesquero (incluyendo la ausencia de explotacion) permitieron la detcccion de algunos patrones y procesos que antes de la clausura de la pesquerfa no eran conocidos. tales como: (I) la relacion stock-reclutamiento fue sobrecornpensatoria, mostrando la inhibicion del reclutamicnto ante altas densidades de adultos: (2) !as tasas de crecimiento de Ios individuos menores a un añ estuvicron relacionadas en forma inversa con la densidad de adultos: (3) la mortalidad natural de Ios individuos menores a un año fue denso-dependiente de la potencia del reclutamiento, aurnentando tarnbien con la actividad pesquera: (4) se encontro una correlacionnegativa altamente significativa entre la intcnsidad de pesca ejercida sobre Mesodesma mactroides y la abundancia del bivalvo simpatrico Donax lzanleyanus Philippi. I Se concluye que el manejo experimental es una herramienta poderosa para identificar Ios factores que gobiernan la dinámica de poblaciones explotadas de playas de arena. Se remarca la necesidad de que futuras investigaciones en el topico incluyan a! hombre como un factor clave en la explicacion de !as tluctuaciones poblacionales a largo plazo. Palabras clavc: Mesodesma mactroides,dinamica poblacional, pesca, largo plazo

Long-term trends in striped venus clam (Chamelea gallina) fisheries in the western Mediterranean Sea: the case of Ebro Delta (NE Spain)

All clam fisheries in the western Mediterranean Sea have dramatically declined in the last few decades. Recently, most have collapsed in Spain, resulting in job loss for hundreds of small-scale fishers. However, insufficient attention has been given to the profound significance of this socio-ecological crisis. We evaluated the historical, social, and ecological context of the striped venus clam (Chamelea gallina) fisheries in the western Mediterranean Sea, focusing on one of the main productive areas of this region (the Ebro Delta, Catalonia, NE Spain) to detect possible causes of the decline in clam landings. Different governance systems (self-governance, centralized governance, and de facto co-governance) had been successful in maintaining striped clam fisheries since they were established in the 1940s. However, since the industrialization of fishing fleets in the mid-1970s, a lack of reliable management (e.g., free access; conflicts between different interested parties) and a progressive increase in fishing capacity, fishing effort, and technological enhancements across the small fishing grounds have increased the vulnerability of the exploited stocks and set them on a collapse trajectory. We recommend the following management measures to promote the recovery of the striped venus clam stock and mitigate the loss of its ecological, social, and economic value: (1) the closure of the fishery in the Ebro Delta; (2) the preparation and implementation of a Spanish Management Fishery Plan to restore the striped clam fishing grounds; (3) the establishment of a supra-regional Management Plan for the striped venus clam on the Mediterranean coast of Spain

Sandy beach social–ecological systems at risk: regime shifts, collapses, and governance challenges

Approximately half of the world’s ice-free ocean coastline is composed of sandy beaches, which support a higher level of recreational use than any other ecosystem. However, the contribution of sandy beaches to societal welfare is under increasing risk from local and non-local pressures, including expanding human development and climate-related stressors. These pressures are impairing the capacity of beaches to meet recreational demand, provide food, protect livelihoods, and maintain biodiversity and water quality. This will increase the likelihood of social–ecological collapses and regime shifts, such that beaches will sustain neither the original ecosystem function nor the related services and societal goods and benefits that they provide. These social–ecological systems at the land–sea interface are subject to market forces, weak governance institutions, and societal indifference: most people want a beach, but few recognize it as an ecosystem at risk.CSIC: Grupos ID 3

Marine debris ingestion by albatrosses in the southwest Atlantic Ocean

Plastics and other marine debris affect wildlife through entanglement and by ingestion. We assessed the ingestion of marine debris by seven albatross species in the southwest Atlantic by analyzing stomach contents of birds killed in fisheries. Of the 128 specimens examined, including four Diomedea species (n = 78) and three Thalassarche species (n = 50), 21 (16.4%) contained 1–4 debris items, mainly in the ventriculus. The most common type was plastic fragments. Debris was most frequent in Diomedea species (25.6%) and, particularly, Diomedea sanfordi (38.9%) and very rare in Thalassarche species (2.0%), presumably reflecting differences in foraging behavior or distribution. Frequency of occurrence was significantly higher in male than female Diomedea albatrosses (39.3% vs. 18.0%). Although levels of accumulated debris were relatively low overall, and unlikely to result in gut blockage, associated toxins might nevertheless represent a health risk for Diomedea albatrosses, compounding the negative impact of other human activities on these threatened species

Long-term trends in striped venus clam (Chamelea gallina) fisheries in the western Mediterranean Sea: the case of Ebro Delta (NE Spain).

All clam fisheries in the western Mediterranean Sea have dramatically declined in the last few decades. Recently, most have collapsed in Spain, resulting in job loss for hundreds of small-scale fishers. However, insufficient attention has been given to the profound significance of this socio-ecological crisis. We evaluated the historical, social, and ecological context of the striped venus clam (Chamelea gallina) fisheries in the western Mediterranean Sea, focusing on one of the main productive areas of this region (the Ebro Delta, Catalonia, NE Spain) to detect possible causes of the decline in clam landings. Different governance systems (self-governance, centralized governance, and de facto co-governance) had been successful in maintaining striped clam fisheries since they were established in the 1940s. However, since the industrialization of fishing fleets in the mid-1970s, a lack of reliable management (e.g., free access; conflicts between different interested parties) and a progressive increase in fishing capacity, fishing effort, and technological enhancements across the small fishing grounds have increased the vulnerability of the exploited stocks and set them on a collapse trajectory. We recommend the following management measures to promote the recovery of the striped venus clam stock and mitigate the loss of its ecological, social, and economic value: (1) the closure of the fishery in the Ebro Delta; (2) the preparation and implementation of a Spanish Management Fishery Plan to restore the striped clam fishing grounds; (3) the establishment of a supra-regional Management Plan for the striped venus clam on the Mediterranean coast of Spain

Distribution of the isopod Excirolana braziliensis on sandy beaches of the Atlantic and Pacific Oceans

We assessed geographic patterns of abundance of the isopodExcirolana braziliensis across its whole distribution range in the context of the abundant centre hypothesis (ACH). We also evaluated auxiliary y potheses to the ACH involving habitat availability and suitability. We compiled species abundance and occurrence information on 139 Pacific and Atlantic sandy beaches of the Americas. Abundance patterns were contrasted against 5 hypothetical distribution models. Habitat availability (sandy beach along the coast), and the role played by grain size on isopod abundance were analysed. Maximum entropy niche modelling based on primary production, salinity, water temperature and tidal range data was used to estimate trends in habitat suitability. E. braziliensis abundance peaked at the 2 edges of its range on the Atlantic coast and towards the centre of its range on the Pacific coast. Congruently, the niche model predicted very low habitat suitability at the centre of the species’ range on the Atlantic coast. Primary production was the main contribution to the model (74.8%). The highest abundances were found in fine sediments (0.20 mm). Support for the ACH forE. braziliensis was found only for the Pacific coast, whereas habitat suitability and availability together with local in-beach morphodynamics accounted for deviations from ACH predictions in the Atlantic. The highest abundances registered in upwelling areas and on beaches with fine sands highlight the primary role played by regional and local conditions over geographic location

Evidence of ocean warming in Uruguay’s fisheries landings: The mean temperature of the catch approach

Distribution, abundance and life history traits of marine fish and invertebrates are increasingly affected by ocean warming. Consequently, landings of traditional fisheries and their relative species composition could potentially be modified. The mean temperature of the catch (MTC) concept, which refers to the average inferred temperature preference of exploited species weighted by their annual catch for a given area, was applied to Uruguay’s industrial fisheries. This approach allowed us to assess the evidence of ocean warming in long-term Uruguayan landings (1973−2017), which were mostly obtained from a major marine warming hotspot. Results showed a marked shift in MTC through time, with the first 10−15 yr characterized by a decreasing trend, but subsequently increasing steadily over time. Long-term effects of ocean warming have led to a shift from cool-water to warm-water species in the relative representation of local landings. A significant and consistent association between sea surface temperature and MTC increase was observed, even when accounting for other drivers. This study provides the first quantitative evidence that ocean warming has been increasingly affecting Uruguayan industrial fisheries during the past decades, and calls for an urgent need to consider environmental changes to properly manage fish stocks, particularly those shared with neighboring countries.Fil: Gianelli, Ignacio. Universidad de la Republica; UruguayFil: Ortega, Leonardo. Dirección Nacional de Recursos Acuáticos; UruguayFil: Marín, Yamandú. Direccion de Recursos Acuaticos; UruguayFil: Piola, Alberto Ricardo. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias de la Atmósfera y los Océanos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Defeo Gorospe, Omar. Universidad de la Republica; Urugua

Sediment grain size determines microplastic exposure landscapes for sandy beach macroinfauna

Despite the global occurrence of microplastic contamination on sandy beaches, evidence of microplastic distribution within beaches remains contradictory. When conflicting evidence is used to inform sampling surveys, it increases uncertainty in resulting data. Moreover, it hampers spatially explicit risk characterization of microplastic pollution to intertidal fauna. We aimed to guide sampling designs for microplastic monitoring on beaches, and to quantify macroinfauna exposure to microplastics. Microplastic abundance, quantified between 5 mm–66 μm, lacked a significant zonation across the top sediment layer of sub-terrestrial, upper and lower midlittoral, and swash zones at two sites with varying anthropogenic influence on a microtidal dissipative beach in Uruguay. Microplastic abundance decreased exponentially with increasing grain size, as revealed by Bayesian Poisson regression, although the decrease was less steep compared to prior knowledge regarding sediment – plastic interactions obtained for large (millimeter-sized) industrial pellets. Significant differences in microplastic contamination between the two sites with varying anthropogenic influence likely related to their proximity to a freshwater canal. Corresponding field measurements of body burdens of fibers and irregular particles were significantly lower for the polychaete Euzonus (Thoracophelia) furcifera, despite its preference for finer sediments with higher microplastic loads, compared to the isopods Excirolana braziliensis and Excirolana armata. Results provide critical insights toward representative sampling of microplastics within beach sites. Specifically, we caution against sampling limited to the drift line, and instead recommend: 1) reporting beach morphodynamic characteristics; 2) using clearly defined, ecologically-informed zonation schemes; and 3) accounting for sediment grain size as a covariate to normalize among reported contamination levels. The results contribute valuable baseline data toward realistic exposure landscapes relative to the sediment grain size preferences of macroinfauna, needed to inform laboratory experiments