Influence of Levantine Artificial Reefs on the fish assemblage of the surrounding seabed

Four Artificial Reef (AR) units were deployed at a 20m depth on a flat hard substrate 3 km west of Haifa, Israel and then surveyed for fish for 12 months. AR units supported 20 times the biomass of control quadrates and their enrichment impact was still significant at a radius of 13m away from units. The 13m values were also significantly higher than those of quadrates adjacent to units, suggesting the existence of a halo of relative depletion within the outer enrichment halo. The main species contributing to this pattern was the migrant herbivore Siganus rivulatus. A decrease in grazing resources is thus suggested as an explanation for creation of this halo. The most consistent AR residents were also Lessepsian migrants - Sargocentron rubrum, nocturnal predators which displayed high microhabitat fidelity and a steady increase in density. The 6 species of migrants recorded accounted for 65.3% of the commercially exploitable biomass and 25.2% of the specimens in the AR site. Other constant AR residents were the groupers Epinephelus costae and Epinephelus marginatus, which are rare and commercially important species. Site protection from fishing and storms were found to be of utmost importance, and design and deployment considerations are discussed

Primera aplicación del Índice de grandes peces (IGP) al Mediterráneo oriental

The composition and structure of fish assemblages caught by trawl in the Levantine Sea (eastern Mediterranean) were summarized using a fishing-sensitive univariate indicator. This metric, called the ‘Large Fish Index’ (LFI), has been developed in the North Sea since 2000 and is applied and adapted here for the first time in the eastern Mediterranean. It was defined as the fish biomass fraction above a pre-determined length threshold, expressed as proportion of the total fish biomass. Trawl-caught assemblages in the warm, oligotrophic, highly invaded Levant were found to be characterized by small fishes. ‘Large fish’ were thus delineated as 20-30 cm (total length) for this region, as opposed to 40 cm set in the North Sea. Desired minimum LFI proportions were set as 0.5 for fishes longer than 20 cm and 0.3 for fishes longer than 30 cm and the actual values found in Israeli bottom trawl surveys from 2008 to 2012 were 0.3 and 0.155 respectively. These low LFI values for the small fishes caught by trawlers attest to the ecological unsustainability and economic inefficiency of bottom trawling in Israel and provide a tool for managers with which to assess the state of the fishery and the general health of the ecosystem.La composición y estructura de las comunidades de peces capturados por arrastre en el mar de Levante (Mediterráneo Oriental) se expresó mediante un indicador univariado sensible a la pesca. Esta medida, denominada “Índice de grandes peces” (IGP), se desarrolló en el Mar del Norte desde 2000 y se aplica y se adapta por primera vez al Mediterráneo oriental. Se define como la fracción de biomasa de peces por encima de un umbral de longitud predeterminada, expresada como proporción de la biomasa total. Se encontró que los conjuntos de peces capturados en el mar de Levante, cálido, oligotrófico, y con muchas especies invasoras se caracterizan por estar formados de peces pequeños. Se definieron los “peces grandes” para esta región aquellos superiores a 20 o 30 cm de longitud total, en lugar de los 40 cm establecidos en el Mar del Norte. Las proporciones mínimas deseables de IGP se establecen en 0.5 para peces de más de 20 cm y 0.3 para los peces de más de 30 cm mientras que los valores reales que se encuentran en las campañas de arrastre de fondo israelíes 2008-2012 fueron 0.3 y 0.155, respectivamente. Estos bajos valores señalan la insostenibilidad ecológica y la ineficiencia económica de la pesca de arrastre en Israel y proporcionan una herramienta para los gestores con los que evaluar el estado de la pesca y la salud general del ecosistema

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

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.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 (1990-1994), 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

Dugoročno istraživanje ulova (1949-2010) i ribolovnog napora izraelskih koćarica u istočnom dijelu Sredozemlja

The trawl fishery of the Mediterranean coast of Israel was analyzed vis á vis catch and fishing effort for the years 1949-2010. The Maximum Sustainable Yield (MSY) was calculated using the Fox surplus-yield model and was found to be 1,413 ton per annum using 1,415 units of effort (fishing days X engine power divided by 1000). Only during nine years (1997-2005) did fishing effort exceed the value for which the yield is the MSY by an average of 184.9 units of effort, but the yield was similar to that of the previous years. During 10 years the catch exceeded the MSY by an average of 153±119 tons. This result was used to justify the “freezing” of the local trawl fleet at the beginning of the 1990’s.Koćarski ulov na sredozemnoj obali Izraela analiziran je s obzirom na ulov i ribolovni napor od 1949. do 2010. godine. Maksimalni održivi prinos (MSY) izračunat je primjenom Fox modela za viši prekomjerni ulov i utvrđeno je da iznosi 1.413 tona godišnje koristeći 1.415 jedinica napora (dani ribolova x motorna snaga podijeljena s 1000). Tijekom devet godina (1997.- 2005.) ribolovni napor premašuje vrijednost čiji maksimalni održivi prinos (MSY) iznosi u prosjeku 184,9 jedinica, dok je prinos bio sličan onome prethodnih godina. Tijekom 10 godina ulov je premašio, maksimalni održivi prinos (MSY) za prosječno 153 ± 119 tona. Taj rezultat je bio upotrebljen kao argument za „zamrzavanje“ lokalne kočarske flote početkom 1990-ih godina

Pojava lesepsijskog migranta Lutjanus argentimaculatus u Sredozemlju, (Actinopterygii: Perciformes: Lutjanidae) prvi zapis s obale Izraela

Two specimens of the Lessepsian migrant, the Mangrove red snapper Lutjanus argentimaculatus are reported from the Mediterranean coast of Israel. L. argentimaculatus was first recorded in the Mediterranean in 1979 by a single specimen. Over three decades later and only in the last two years four specimens, including the two reported herein, were recorded. This pattern strongly suggests that L. argentimaculatus has established a sustainable population in the Mediterranean.U radu se opisuje prvi nalaz dva primjerka lesepsijskog migranta Lutjanus argentimaculatus na Izraelskoj obali. Prvi nalaz jednog primjerka vrste Lutjanus argentimaculatus zabilježen je 1979. godine u Sredozemnom moru. Trideset godina nakon tog nalaza i to u posljednje dvije godine zabi-lježen je nalaz četiri primjerka uključujući dva navedena u ovom radu. Na temelju nalaza izvidno je da je vrsta Lutjanus argentimaculatus uspostavila populaciju u Sredozemlju

Phenological shift in swarming patterns of Rhopilema nomadica in the Eastern Mediterranean Sea

Jellyfish (JF) swarms impact human wellbeing and marine ecosystems. Their global proliferation is a matter of concern and scientific debate, and the multitude of factors affecting (and affected by) their density and distribution merits long-term monitoring of their populations. Here we present an eight-year time series for Rhopilema nomadica, the most prominent JF species swarming the Eastern Mediterranean Sea. Reports were submitted by the public and within it a group of trained participants via an internet website between June 2011 and June 2019. Data collected included species, size, location, ranked amount and stinging. Swarms of R. nomadica prevailed in July and ended in August but were also prominent in winter from January to March. Both observations deviate from past swarming patterns described in the late 1980s, when summer swarms persevered until October and winter swarms were not documented. Climate change (increasing water temperature) and the westwards up-current spread of R. nomadica are discussed as possible explanations for this phenological shift

Izrael: Rekonstruirane procjene ukupnog izlova u Sredozemnom moru, 1950.–2010.

Over the past six decades, the Food and Agriculture Organization (FAO) has reported fisheries ‘landings’, not ‘total removals’ for Israel. Thus, public data do not include all removals, including discards, the recreational fishery, subsistence portions of the catch or Bluefin tuna catches. Moreover, FAO data inadvertently included landings by Gaza fishers in the Gaza Strip during the 1960s and 1970s. We reconstructed total removals for Israel fishing in the Mediterranean Sea using various anchor points from recent studies to account for the missing removals. We estimated total removals at slightly over 255,400 tonnes for 1950-2010, which are nearly 30% higher than the 198,136 t of Israel’s reported catch to FAO (after exclusion of data from the Gaza Strip). The major components of unreported removals were discards (over 37,400 t), dominated by the trawl fishery, and recreational removals (over 15,500 t), which account for a large and rapidly growing fishery sector in Israel. In contrast, subsistence catches (just under 4,000 t) are low, which is not unexpected for a developed country. Non-indigenous Indo-Pacific organisms are a large and growing component in the multispecies catch of Mediterranean fishers; however they appear to change species composition and mode of exploitation more than they affect the level of total removals. In the highly oligotrophic, yet fast changing Levantine Sea, the high discarding rates, use of unsustainable fishing methods and under-regulated fisheries (particularly the recreational sector) pose a threat to the integrity of the marine environment and the ecosystem services we expect from it.Tijekom proteklih šest desetljeća, FAO je davao izvješća o ulovu (iskrcajnom ulovu), ali ne i o ukupnom izlovu za Izrael. Stoga, javni podaci ne uključuju sve izlove, uključujući odbačeni ulov, ulov u rekreacijskom ribolovu, ulove u dopunskom ribolovu kao i ulove plavoperajne tune. Štoviše, FAO podaci nehotice uključuju i ulov ribara u pojasu Gaze tijekom 1960-ih i 1970- ih. Rekonstruirani su ukupni izlovi za Izraelski ribolov u Sredozemnom moru, koristeći razna polazišta iz nedavnih studija kako bi se obračunali nedostajući podaci o sveukupnom izlovu. Procijenjen ukupni izlov iznosi nešto više od 255.400 tona za razdoblje od 1950.-2010., koji je gotovo 30% veći od 198.136 t izraelskog prijavljenog ulova prema FAO (nakon odbacivanja podataka iz pojasa Gaze). Glavne komponente neprijavljenih izlova su: odbačeni ulov (preko 37.400 t), u kojem dominira koćarski ribolov, i rekreacijski izlov (preko 15.500 t), koji čini veliki i brzo rastući sektor ribarstva u Izraelu. Nasuprot tome, ulovi u dopunskom ribolovu (nešto manje od 4.000 t) su niski, što i nije neočekivano za razvijene zemlje. Strani organizmi iz Crvenog mora su velika i rastuća komponenta u ulovima mediteranskih ribara, no čini se da će isti promijeniti sastav vrsta kao i način iskorištavanja živih bogatstava znatno više nego što recimo utječu na razini ukupnog izlova. U vrlo oligotrofnom, ali i brzo mijenjajućem Levantskom moru, velike količine odbačenog ulova, postojeća uporaba neodrživih metoda ribolova kao i slabo reguliran ribolov (osobito unutar rekreativnog sektora) predstavljaju prijetnju integritetu morskog ekosustava te ujedno time i onome što možemo očekivati od njega

Community management indicators can conflate divergent phenomena: two challenges and a decomposition-based solution

1. Community indicators are used to assess the state of ecological communities and to guide management. They are usually calculated from monitoring data, often collected annually. Since any given community indicator provides a univariate summary of complex multivariate phenomena, different changes in the community may lead to the same response in the indicator. Sampling variation can also mask ecologically important trends. 2. This study addresses these challenges for community indicators, with a focus on the large fish indicator (LFI), internationally used to report status of marine fish communities. The LFI expresses ‘large’ fish biomass as a proportion of total fish biomass and is calculated from species–size–abundance data collected on trawl surveys. We develop new methods to decompose the contributions of species, sampling locations and season to trends over time in the LFI, and highlight consequences for assessment and management. 3. Our results showed that both species and locations made divergent contributions to overall trends in the LFI indicator, with contributions differing by several orders of magnitude and in sign. Only small proportions of species and locations drove overall LFI trends, and their contributions changed with season (spring and autumn surveys). To assess significance of component trends, a resampling method was developed. Our method can be generalised and applied to many other community indicators based on survey data. 4. Synthesis and applications. Our new method for decomposing community indicators and generating confidence intervals makes it possible to extract much more information on what drives a ‘headline’ indicator, providing a solution to challenges arising from multiple possible interpretations of changes in the indicator, and from sampling variation. Analysis of the effects of indicator components on headline indicator values is recommended, because the results allow assessors and managers to identify and interpret how divergent factors (e.g. species, sampling locations and seasons) contribute to the headline indicator value

Old Info for a New Fisheries Policy: Discard Ratios and Lengths at Discarding in EU Mediterranean Bottom Trawl Fisheries

Discarding is considered globally among the most important issues for fisheries management. The recent reform of the Common Fisheries Policy establishes a landing obligation for the species which are subject to catch limits and, in the Mediterranean, for species which are subject to Minimum Conservation Reference Size (MCRS) as defined in Annex III to Regulation (EC) No 1967/2006. Additionally, several other initiatives aim to reduce unwanted catches of target and bycatch species, including species of conservation concern. This raises the need to study discarding patterns of (mainly) these species. In this work we collated a considerable amount of historical published information on discard ratios and lengths at discarding for species caught in EU Mediterranean bottom trawl fisheries. The main aim was to summarize the available historical records and make them more accessible for scientific and managerial needs, as well as to try identifying patterns in discarding. We show discard ratios and lengths at which 50% of the individuals were discarded (L50) for 15 species (9 bony fishes, three crustacean decapods, and three elasmobranchs). Discard ratios were usually low for target species such as hake, red mullets and highly commercial shrimps and exemptions from the landing obligation under the de minimis rules could be sought in several cases. Discard ratios were usually higher for commercial bycatch species. Discarding is affected by a combination of factors and for a given species, especially for non-target ones, discards are likely to fluctuate within a fishery, across seasons, years, and regions. For most species considered, L50s were lower than the MCRS (when in place) and length at first maturity. L50s of target species, such as hake, were very small due to the existence of market demands for small sized individuals. However, for species of low demand, like horse mackerels, a higher retention size was observed, often exceeding MCRS. Lengths at discarding are affected by legal provisions, market demands but also by biological, population, and ecological traits. Understanding the factors that affect discarding constitutes the starting point for designing mitigation measures and management plans to reduce discards and improve the sustainability of the stocksVersión del edito

Management priorities for marine invasive species

Managing invasive alien species is particularly challenging in the ocean mainly because marine ecosystems are highly connected across broad spatial scales. Eradication of marine invasive species has only been achieved when species were detected early, and management responded rapidly. Generalized approaches, transferable across marine regions, for prioritizing actions to control invasive populations are currently lacking. Here, expert knowledge was elicited to prioritize 11 management actions for controlling 12 model species, distinguished by differences in dispersion capacity, distribution in the area to be managed, and taxonomic identity. Each action was assessed using five criteria (effectiveness, feasibility, acceptability, impacts on native communities, and cost), which were combined in an ‘applicability’ metric. Raising public awareness and encouraging the commercial use of invasive species were highly prioritized, whereas biological control actions were considered the least applicable. Our findings can guide rapid decision-making on prioritizing management options for the control of invasive species especially at early stages of invasion, when reducing managers' response time is critical