Marine Protected Areas as a central element of ecosystem-based management: defining their location, size and number

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Razvoj grčkog ribarstva tijekom razdoblja 1928. -1939.

In the present study, Greek fisheries landings were extended back to 1928, for the first time, from data derived by the General Statistical Service of Greece during the 1928-1939 period. In particular, we: (a) present the annual fisheries landings for all species combined, fishing effort for all gear-types combined and species-specific landings during 1928-1939, (b) re-allocate the spatial resolution of landings during 1928-1939 to that during 1964-2007, and (c) compare the landings for different periods during 1928-2007. Results showed that during 1928-1939, landings and effort generally increased. The time series of all species landings exhibited a strong between-year variability, with 23 out of 40 species displaying a significant increasing trend. The analysis of fisheries landings over time (1928-2007) displayed four distinct patterns corresponding to four phases of Greek fisheries development: (1) a gradual increase during 1928-1949 (pre-development phase of fisheries), (2) a steeper increase during 1950-1969 (growth phase), (3) a much steeper linear increase during 1970-1994 (fully tο over-exploited phase) and (4) a declining trend during 1995-2007 (collapse phase). These phases coincided chronologically with significant socio-economic and political events that took place in Greece since 1928.U ovom radu, po prvi put, je iznesen status ulova u grčkom ribarstvu i to u razdoblju od 1928. do 1939. godine prema podacima iz Opće statističke službe u Grčkoj. Konkretno, izneseno je slijedeće: a) predstavljen je godišnji ulov ribarstva za sve vrste zajedno, ribolovni napor za sve vrste alata u kombinaciji i vrste specifičnih ulova tijekom razdoblja 1928.-1939., b) ponovno dodijeljive prostorne rezolucije ulova tijekom 1928.-1939., te tijekom 1964.-2007., i c) uspoređen je ulov za različita razdoblja tijekom 1928.-2007. Rezultati su pokazali da su se tijekom 1928.-1939., ulov i ribolovni napor općenito povećali. Vremenske serije svih vrsta ulova su bile izložene jakim međugodišnjim varijabilnostima, te od 40 vrsta njih 23 su pokazale značajan trend rasta. Analiza ukupnog ulova ribarstva tijekom vremena (1928.-2007.) prikazuje četiri različita uzoraka koji obilježavaju četiri faze razvoja grčkog ribarstva: 1. postupno povećavanje tijekom 1928.-1949. (pred-faza razvoja ribarstva), 2. strmo povećanje tijekom 1950.-1969. (faza rasta), 3. značajan linearni porast tijekom 1970.-1994. (faza potpunog dο prekomjernog ulova) i 4. opadajući trend tijekom 1995.-2007. (kolaps faza). Ove faze se kronološki poklapaju sa značajnim socio-ekonomskim i političkim događanjima koja su se zbivala u Grčkoj od 1928. godine

Prehrana i hranilišta traglja Spicara maena i gire S. smaris (Pisces, Osteichthyes, Centracanthidae) u sjevernom dijelu Egejskog mora

n the present paper we studied the diet of two centracanthid species , Spicara maena and S. smaris,in the N Aegean Sea. Overall, 282 and 118 individuals were examined, respectively. Both species preyed upon zooplankton, notably Copepoda (54.3 and 63.5%, respectively). S. maena included in its diet a wider variety of food items (36 taxa) compared to S. smaris (12 taxa). The individual trophic levels for both species ranged from 3.00 to 4.50 (mean values ± strandard error: 3.21±0.058 for S. maena and 3.05±0.068 for S. smaris ). Given their trophic position and local abundance, they play a crucial role in the flux of energy from low to high trophic levels of the Aegean benthic and pelagic food webs.U ovom radu prikazani su rezultati istraživanja prehrane dviju vrsta iz porodice girovki, traglja Spicara maenai gire S. smaris, sa sjevernog područja egejskog mora. Istraženo je 282 jedinki traglja te 118 jedinki gire. Obje vrste u svojoj prehrani koriste zooplankto, osobito veslonošcec opepoda (54.3% tragalj, 63.5% gira). Tragalj u svojoj prehrani koristi znatno širi raspon organizama (36 svojti) dok gira znatno manje (12 svojti). Pojedinačna trofička razina za obje vrste se kreće od 3.00 do 4.50 (srednja ijednost±standardna pogreška: 3.21±0.058 za traglja i 3.05±0.068 za giru).glede njihove trofičke razine i lokalne brojnosti, obje vrste igraju značajnu ulogu u protoku energije od najnižih do najviših trofičkih razina u e gejskom moru u okviru pelagijskog i bentoskog lanca prehrane

The “discard problem” in Mediterranean fisheries, in the face of the European Union landing obligation: the case of bottom trawl fishery and implications for management

Since the first introduction of the landing obligation (a.k.a. Discard ban) in 2015, the EU Mediterranean fisheries are facing some unforeseen challenges. The demersal bottom trawl fisheries, being the most significant contributors to the so-called 'discard problem', are confronted with the greatest challenges. Data from the Italian and the Greek fleet, spanning over two decades (1995–2015), were analysed with the intention of revealing the diversity and heterogeneity of the discard problem, especially for regulated species. Species composition of discards, as well as discarding rates, were shown to be irregular, fluctuating among areas, depth strata, seasons and years. Although fish dominated the discarded gross catch in weight, benthic invertebrates (other than commercial cephalopods and crustaceans) were the taxa discarded almost exclusively. The established minimum conservation reference size was largely ignored by fishers. From a management point of view, the present investigation suggests that the recently established Discard Management Plans lack scientific evidence (given the high intrinsic variability of the parameters and confusion regarding the rules) and provide exemptions from the landing obligation that will in practice allow the average Mediterranean bottom trawl vessel to continue business as usual. Moreover, detecting if these rules are actually respected is an almost impossible task for the Mediterranean control and enforcement authorities. Incentivizing the adoption of fishing technologies and practices that reduce pre-harvest mortality and post-harvest discards, while avoiding damage to sensitive marine species and habitats, seems the only way to move forward, rather than dealing with the problem after it has occurred

Trammel net catch species composition, catch rates and metiers in southern European waters: A multivariate approach

We identified and quantified the effect of season, depth, and inner and outer panel mesh size on the trammel net catch species composition and catch rates in four southern European areas (Northeast Atlantic: Basque Country, Spain; Algarve, Portugal; Gulf of Cadiz, Spain; Mediterranean: Cyclades, Greece), all of which are characterised by important trammel net fisheries. In each area, we conducted, in 1999-2000, seasonal, experimental fishing trials at various depths with trammel nets of six different inner/outer panel mesh combinations (i.e., two large outer panel meshes and three small inner panel meshes). Overall, our study covered some of the most commonly used inner panel mesh sizes, ranging from 40 to 140 mm (stretched). We analysed the species composition and catch rates of the different inner/outer panel combinations with regression, multivariate analysis (cluster analysis and multidimensional scaling) and other 'community' techniques (number of species, dominance curves). All our analyses indicated that the outer panel mesh sizes used in the present study did not significantly affect the catch characteristics in terms of number of species, catch rates and species composition. Multivariate analyses and seasonal dominance plots indicated that in Basque, Algarve and Cyclades waters, where sampling covered wide depth ranges, both season and depth strongly affected catch species compositions. For the Gulf of Cadiz, where sampling was restricted to depths 10-30 m, season was the only factor affecting catch species composition and thus group formation. In contrast, the inner panel mesh size did not generally affect multidimensional group formation in all areas but affected the dominance of the species caught in the Algarve and the Gulf of Cadiz. Multivariate analyses also revealed 11 different metiers (i.e., season-depth-species-inner panel mesh size combinations) in the four areas. This clearly indicated the existence of trammel net 'hot spots', which represent essential habitats (e.g., spawning, nursery or wintering grounds) of the life history of the targeted and associated species. The number of specimens caught declined significantly with inner panel mesh size in all areas. We attributed this to the exponential decline in abundance with size, both within- and between-species. In contrast, the number of species caught in each area was not related to the inner mesh size. This was unexpected and might be a consequence of the wide size-selective range of trammel nets. (c) 2006 Elsevier B.V All rights reserved

Habitat Selection and Temporal Abundance Fluctuations of Demersal Cartilaginous Species in the Aegean Sea (Eastern Mediterranean)

Predicting the occurrence of keystone top predators in a multispecies marine environment, such as the Mediterranean Sea, can be of considerable value to the long-term sustainable development of the fishing industry and to the protection of biodiversity. We analysed fisheries independent scientific bottom trawl survey data of two of the most abundant cartilaginous fish species (Scyliorhinus canicula, Raja clavata) in the Aegean Sea covering an 11-year sampling period. The current findings revealed a declining trend in R. clavata and S. canicula abundance from the late ′90 s until 2004. Habitats with the higher probability of finding cartilaginous fish present were those located in intermediate waters (depth: 200–400 m). The present results also indicated a preferential species' clustering in specific geographic and bathymetric regions of the Aegean Sea. Depth appeared to be one of the key determining factors for the selection of habitats for all species examined. With cartilaginous fish species being among the more biologically sensitive fish species taken in European marine fisheries, our findings, which are based on a standardized scientific survey, can contribute to the rational exploitation and management of their stocks by providing important information on temporal abundance trends and habitat preferences

Inferring fish escape behaviour in trawls based on catch comparison data: Model development and evaluation based on data from Skagerrak, Denmark

During the fishing process, fish react to a trawl with a series of behaviours that often are species and size specific. Thus, a thorough understanding of fish behaviour in relation to fishing gear and a scientific understanding of the ability of different gear designs to utilize or stimulate various behavioural patterns during the catching process are essential for developing more efficient, selective, and environmentally friendly trawls. Although many behavioural studies using optical and acoustic observation systems have been conducted, harsh observation conditions on the fishing grounds often hamper the ability to directly observe fish behaviour in relation to fishing gear. As an alternative to optical and acoustic methods, we developed and applied a new mathematical model to catch data to extract detailed and quantitative information about species- and size-dependent escape behaviour in towed fishing gear such as trawls. We used catch comparison data collected with a twin trawl setup; the only difference between the two trawls was that a 12 m long upper section was replaced with 800 mm diamond meshes in one of them. We investigated the length-based escape behaviour of cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), witch flounder (Glyptocephalus cynoglossus), and lemon sole (Microstomus kitt) and quantified the extent to which behavioural responses set limits for the large mesh panel's selective efficiency. Around 85% of saithe, 80% of haddock, 44% of witch flounder, 55% of lemon sole, and 55% of cod (below 68 cm) contacted the large mesh panel and escaped. We also demonstrated the need to account for potential selectivity in the trawl body, as it can bias the assessment of length-based escape behaviour. Our indirect assessment of fish behaviour was in agreement with the direct observations made for the same species in a similar section of the trawl body reported in the literature

Fishery Discards: Factors Affecting Their Variability within a Demersal Trawl Fishery

Discards represent one of the most important issues within current commercial fishing. It occurs for a range of reasons and is influenced by an even more complex array of factors. We address this issue by examining the data collected within the Danish discard observer program and describe the factors that influence discarding within the Danish Kattegat demersal fleet over the period 1997 to 2008. Generalised additive models were used to assess how discards of the 3 main target species, Norway lobster, cod and plaice, and their subcomponents (under and over minimum landings size) are influenced by important factors and their potential relevance to management. Our results show that discards are influenced by a range of different factors that are different for each species and portion of discards. We argue that knowledge about the factors influential to discarding and their use in relation to potential mitigation measures are essential for future fisheries management strategies