Aim We examine fish invasions in the south-eastern Mediterranean as a model system for the invasibility of open coasts and provide perspectives through a review of global marine fish invasions.Location South-eastern Mediterranean (Levant Sea).Methods We compare historical (1990-1994) and modern (2008-2011) trawl surveys from the Mediterranean continental shelf and upper slope of Israel to evaluate the relative abundance and biomass of Indo-Pacific fishes and their impact on diversity and trophic level (TrL). We examine resultant changes in community composition by both univariate and multivariate analyses, and compliment this study with a critical global review of open coast marine fish invasions.Results A staggering 55 Indo-Pacific fish species have established permanent populations in the Mediterranean in the last 142 years, more than any other marine ecosystem. This process is accelerating with 13 of 27 new arrivals having established in the 21st century alone. Invasive fish biomass and abundance proportions in the shallow open coast have doubled in just two decades and today the Levantine ecosystem is dominated by non-native species. This proliferation has resulted in significant declines of some indigenous species, some to near extirpation levels.Main conclusions Here, we show that non-estuarine ecosystems are much more susceptible to large-scale invasion pressures than previously thought. Our results place invasion in the same category with overexploitation, habitat destruction and pollution, processes normally considered as much more critical perturbations to coastal fish communities. We propose that despite these irreversible alterations, invasions have masked overall TrL changes and diversity declines by replacing native fish with invasives of similar ecological position. As species extirpations increase, we anticipate further declines in indigenous biomass, abundance and diversity in the Mediterranean Sea.

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We compared the antipredator mechanisms of 3 morphological 'types' of lobsters: slipper lobsters Scyllarides latus, spiny lobsters Palinurus elephas and clawed lobsters Homarus gammarus. These lobsters differ in the extent and effectiveness of their weaponry and armor, which we assessed by: (1) field tethering experiments that compared relative survival of intact and manipulated (clinging ability, antennae, or claws removed) lobsters in the face of predation, and (2) measurements of the breaking strength and thickness of the carapace of each species. Intact clawed lobsters suffered higher mortality than either intact slipper or spiny lobsters after both 4 and 24 h. At 24 h, intact spiny lobsters also had higher mortality than intact and manipulated slipper lobsters. The intact spiny and clawed lobsters suffered less predation after 4 h than the manipulated lobsters (lacking weapons); however, this advantage diminished or vanished by 24 h. This indicates that weapons provided some measure of protection in the short-term, which might be sufficient to allow the lobsters to escape from a predator using a strong abdominal tail flip. Triggerfish Balistes carolinensis were the primary predators on the lobsters. We also saw octopuses Octopus vulgaris feeding on lobsters, but these were never observed subduing a live lobster. 'Punch'-tests (i.e. puncture tests) on the carapaces of each of the 3 species showed that slipper lobsters had stronger armor than either spiny or clawed lobsters, while the spiny lobster armor was intermediate in strength. These results suggest that the defensive strong armor of slipper lobsters is a more effective antipredatory mechanism than the offensive morphological weapons of the spiny and clawed lobsters.

SUMMARY:The spatiotemporal patterns of discards and catch composition of Israeli trawlers were examined using a 4-year (1990-1994), 324 haul dataset. Haul depth was found to be the main grouping variable for hauls, although significant seasonal differences were also found. 28.3% of the total catch was discarded, and there was a 40.1% discard percentage in shallow hauls. According to these figures, annual discards for the Israeli trawl fleet for the study period are estimated at ca. 440 to 700 t. Both the biomass and the number of discarded specimens peaked in summer, as well as the percentage of juvenile fish of commercial species. These findings suggest that a summer moratorium on trawling would reduce discards. The percentage of specimens of Indo-Pacific origin decreased from 51% in depths shallower than 37 m to 24% between 38 and 73 m, and 8% in deeper strata. Discards along the Israeli coast were comparable to those observed elsewhere in the Mediterranean. The findings presented here are the first quantitative account of fish community assemblages in the nearshore waters of the easternmost part of the Mediterranean, and thus provide valuable information for comparisons with more current datasets that are currently being assembled.Keywords: bottom-trawl, Israel, discards, catch composition, Lessepsian migration, fishery management. RESUMEN:Patrones espacio-temporales de la captura y los descartes de pesquería de arrastre mediterránea israelí al inicio de la década de los noventa: perspectivas ecológicas y de conservación. -Se analizaron los patrones espacio-temporales de los descartes y la composición de la captura de la flota de arrastre de Israel utilizando datos de 4 años (1990)(1991)(1992)(1993)(1994), 324 caladas. La profundidad resultó ser el principal factor en la agrupación de las caladas, si bien se encontraron asimismo diferencias significativas entre estaciones. Se descartó el 28.3% de la captura total, alcanzándose el 40.1% en las caladas realizadas en las aguas más someras. Según estos porcentajes, se estimó una captura anual descartada por la flota de Israel en ese período de 440-700 t. La biomasa, el número de ejemplares descartados, así como el porcentaje de juveniles de especies comerciales fue mayor en verano. Estos resultados sugieren que una veda de arrastre en verano favorecería la disminución de la captura descartada. El porcentaje de ejemplares de origen indo-pacífico descendió desde 51% en aguas de una profundidad inferior a 37 m, al 24% entre 38-73 m y al 8% en el estrato más profundo. Los descartes en la costa israelí fueron similares a los observados en otras zonas del Mediterráneo. Se presentan por primera vez resultados cuantitativos relativos a comunidades de las aguas costeras del extremo oriental del Mediterráneo, aportándose información para su comparación con datos más recientes que en la actualidad están siendo obtenidos.Palabras clave: arrastre de fondo, Israel, descartes, composición de la captura, migración lessepsiana, gestión de pesquerías.