Calibration for nonlinear mixed effects models: an application to the withdrawal time prediction

We propose calibration methods for nonlinear mixed effects models. Using an estimator whose asymptotic properties are known, four different statistics are used to perform the calibration. Simulations are carried out to compare the performance of these statistics. Finally, the milk discard time prediction of an antibiotic, which has motivated this study, is performed on real data.     

Fishery of the Deep-water Rose Shrimp Parapenaeus longirostris (Lucas, 1846) (Crustacea: Decapoda) in the Northern Tyrrhenian Sea (Western Mediterranean)

The aim of this study is to provide information on the fishing pattern of Parapenaeus longirostris in the northern Tyrrhenian Sea (western Mediterranean), in order to improve the management of the resource in the area. Data were obtained from commercial fishery, covering the period 1991–2002. Catch rates revealed notable inter-annual fluctuation of the P. longirostris landing, probably due to the life cycle of the species. The highest yields (kg per hour of trawl) of the commercial fishery were obtained at depths ranging between 180 and 300 m, the lower ones at depths between 100 and 180 m, where small specimens are more abundant. Commercial catches were characterised by a very low presence of specimens smaller than 20 mm carapace length (CL), mainly due to the deeper localisation of the fishing grounds when compared to the recruitment areas of the species. The size at which 50% of the specimens were discarded by the fishermen was 15 mm CL, while the estimated size at first capture of the individuals caught by the commercial net was 12.4 mm CL.     

A junk-food hypothesis for gannets feeding on fishery waste

Worldwide fisheries generate large volumes of fishery waste and it is often assumed that this additional food is beneficial to populations of marine top-predators. We challenge this concept via a detailed study of foraging Cape gannets Morus capensis and of their feeding environment in the Benguela upwelling zone. The natural prey of Cape gannets (pelagic fishes) is depleted and birds now feed extensively on fishery wastes. These are beneficial to non-breeding birds, which show reduced feeding effort and high survival. By contrast, breeding gannets double their diving effort in an attempt to provision their chicks predominantly with high-quality, live pelagic fishes. Owing to a scarcity of this resource, they fail and most chicks die. Our study supports the junk-food hypothesis for Cape gannets since it shows that non-breeding birds can survive when complementing their diet with fishery wastes, but that they struggle to reproduce if live prey is scarce. This is due to the negative impact of low-quality fishery wastes on the growth patterns of gannet chicks. Marine management policies should not assume that fishery waste is generally beneficial to scavenging seabirds and that an abundance of this artificial resource will automatically inflate their populations.     

Behaviour impairment in captured and released sablefish: ecological consequences and possible substitute measures for delayed discard mortality

Sablefish Anoplopoma fimbria aged 1+ and 2+ years were towed for 4 h in a net, transferred to air for either 15 or 30 min, and then held in tanks for up to 35 days for observation of physical injury, immediate mortality, behaviour impairment, delayed mortality and total mortality. Behaviour was impaired for at least 3 h and returned to normal levels by 24 h after stress induction. Behaviour impairment was correlated with delayed mortality in 2+ year fish but not in 1+ year fish which showed greater variation in stress responses. The results of this study and a review of past discard and escapee studies showed that substitute measures for delayed mortality in the field should include physical injury and behaviour impairment. These two measures integrate the effects of capture‐related stressors which can produce and magnify physical and physiological injury, resulting in changes in fish condition and delayed mortality.     

Extended Life Cycle Assessment of Southern Pink Shrimp Products Originating in Senegalese Artisanal and Industrial Fisheries for Export to Europe

Southern pink shrimp (Penaeus notialis) are an important Senegalese export commodity. Artisanal fisheries in rivers produce 60%. Forty percent are landed in trawl fisheries at sea. The shrimp from both fisheries result in a frozen, consumer‐packed product that is exported to Europe. We applied attributional life cycle assessment (LCA) to compare the environmental impact of the two supply chains and identify improvement options. In addition to standard LCA impact categories, biological impacts of each fishery were quantified with regard to landed by‐catch, discard, seafloor impact, and size of target catch. Results for typical LCA categories include that artisanal fisheries have much lower inputs and emissions in the fishing phase than does the industrial fishery. For the product from artisanal fisheries, the main part of the impact in the standard LCA categories occurs during processing on land, mainly due to the use of heavy fuel oil and refrigerants with high global warming and ozone depletion potentials. From a biological point of view, each fishery has advantages and drawbacks, and a number of improvement options were identified. If developing countries can ensure biological sustainability of their fisheries and design the chain on land in a resource‐efficient way, long distance to markets is not an obstacle to sustainable trading of seafood products originating in artisanal fisheries.     

Demersal trawl discards with spatial and bathymetric emphasis in the Turkish coast of the Aegean Sea

The aim of the present study is to investigate the spatial and bathymetric distribution of demersal trawl discards in the Turkish coast of the Aegean Sea. Trawl hauls were performed in the legal trawling areas of the Turkish coast of the Aegean Sea (Çanakkale, Foça, Karaburun, S??ac?k, Güllük) between 2010 and 2012 by commercial trawlers. Depth of the trawl hauls ranged from 30?m in the south to 450?m in the north. As a result of 311 trawl samples, 200 species belonging to eight taxonomic groups (Porifera, Cnidaria, Annelida, Arthropoda, Mollusca, Echinodermata, Tunicata, Chordata) were identified. The changes in species composition based on depth and region were determined to be statistically significant. It was found that species composition distinctly changed around 200?m. In a regional assessment it was determined that the Turkish coast of the Aegean Sea is divided into three sub-regions, i.e. Çanakkale, Foça-Karaburun-S??ac?k and Güllük. The results of similar studies conducted in the Mediterranean were investigated and compared with the findings of this study.     

Commercial fisheries,inter‐colony competition and sea depth affect foraging location of breeding Scopoli's Shearwaters Calonectris diomedea

The distribution of seabirds at sea is influenced by physical, ecological and anthropogenic factors such as sea depth, prey distribution, intra‐specific competition and commerical fishing activities. We quantified the foraging habitat preferences of Scopoli's Shearwater Calonectris diomedea in the Mediterranean Sea. We analysed habitat preferences in relation to a suite of physical and ecological variables including sea depth, net primary production and distance to other colonies (as a proxy of intra‐specific competition). Since the Mediterranean is heavily impacted by commercial fisheries, we also incorporated the distance to fishing harbours in our analyses as a proxy of the availability of discards which are a potential feeding source for Scopoli's Shearwater. Foraging birds preferred shallower waters and avoided areas close to other colonies, thereby reducing interactions with conspecifics. We also found that long‐distance trips were undertaken to areas close to fishing harbours, suggesting that these represented particularly profitable locations to compensate for the greater travelling costs involved. No differences in foraging between the sexes were recorded. This study improves our understanding of the at‐sea distribution and habitat preference of a seabird inhabiting the over‐exploited Mediterranean Sea. Our results support growing evidence that seabirds exhibit complex relationships with commerical fishing activities, which must be considered when planning conservation programmes.     

Preliminary assessment of discards survival in a multi‐species Mediterranean bottom trawl fishery

The EU Common Fisheries Policy (CFP) reform establishes a gradual landing obligation for stocks for which catch limits are set, and in the Mediterranean for species with Minimum Conservation Reference Size. However, the landing obligation will not apply for species with scientific evidence of high survival rates. Discards estimates usually assume that the whole discarded catch is dead or dies at sea. However, survival of individuals discarded at sea is substantial for several species. In the Mediterranean Sea, the information on this issue is very limited. The aim of this study is to perform a preliminary assessment of the short‐term survival of discards in the multi‐species bottom trawl fishery in the Eastern Ionian Sea, Greece. Experimental fishing was held in spring when no water column stratification was observed and in autumn when a seasonal thermocline was formed. The catch was sorted, the regularly discarded species/sizes were put in tanks and their survival was monitored in specific time intervals up to 72 hr. A seasonal effect was obvious with high mortality in autumn being attributed to high water temperatures. Survival was low or zero for most species, but was relatively high for certain species (e.g., annular seabream, Diplodus annularis (Linnaeus, 1758); European conger, Conger conger (Linnaeus, 1758); brown comber, Serranus hepatus (Linnaeus, 1758) among bony fishes) and broad taxonomic categories (elasmobranchs and most invertebrates) in spring or in both seasons. Poor survival was generally estimated for most species subject to the landing obligation (e.g., hake, Merluccius merluccius (Linnaeus, 1758)). The present study, even though preliminary, can be important for improving future works, for identifying species with high survival potential, and—to a lesser extent—for the implementation of the CFP.     

Survival of discarded plaice (Pleuronectes platessa) from Norway lobster (Nephrops norvegicus) otter‐trawl fishery

The introduction of landing obligations in the European Union common fisheries policy, has increased the focus on discard survival. Since species with scientifically proven high survival rates may be exempted from the landing obligations, the economic significance for the fishing industry is large. Landing obligations include individuals below the minimum conservation reference size (MCRS), which are not allowed to be sold for human consumption. The Norway lobster (Nephrops norvegicus) fishery is a high value fishery, but with a substantial amount of bycatch of plaice (Pleuronectes platessa) below the MCRS. In the present study, observations were made on the short‐term survival of plaice at or below the MCRS, discarded from a small otter board trawler targeting Nephrops in Skagerrak (ICES 3a). The average short‐term survival of plaice was 15% at haul level, ranging from 0% to 39%, after 10 days of captive observation. Survival significantly decreased with time on deck and the retention of debris in the codend (p < 0.0001), while survival was not correlated to size. Vitality assessments, using a combined reflex impairment and injury score, were tested as predictor of survival and were significantly associated to survival (p < 0.0001) both for individual fish and when grouped by hauls. Seabird predation behaviour was assessed and it was estimated that seabirds predated or pursued 85% of discarded plaice below the MCRS.     

Life Cycle assessment of frozen cod fillets including fishery-specific environmental impacts

Goal, Scope and Background  The purpose of the present study was to perform an environmental assessment for the entire life cycle of a seafood product and to include fishery-specific types of environmental impact in inventory and assessment. Environmental data for a frozen block of cod fillets was collected and used for a Life Cycle Assessment, including the fishery-specific environmental aspects seafloor use and biological extraction of target, by-catch and discard species. The fishery takes place in the Baltic Sea where cod is mainly fished by benthic trawls and gillnets. Methods  The functional unit was a consumer package of frozen cod fillets (400 g) reaching the household. Data was gathered from fishermen, fishery statistics, databases, companies and literature. Fishery-specific issues like the impact on stocks of the target and by-catch species, seafloor impact and discarding were quantified in relation to the functional unit and qualitative impact assessment of these aspects was included. Results  Findings include the fact that all environmental impact categories assessed (Global Warming Potential, Eutrophication Potential, Acidification Potential, Photochemical Ozone Creation Potential and Aquatic Ecotoxiciy) are dominated by the fishery. Around 700 m² of seafloor are swept by trawls and around 50 g of under-sized cod and other marine species are discarded per functional unit. The phases contributing most to total environmental impact following fishery were transports and preparation in the household. The process industry and municipal sewage treatment cause considerable amounts of eutrophying emissions. Conclusions  Conclusions are that there are considerable options for improvement of the environmental performance of the seafood production chain. In the fishery, the most important environmental measure is to fish sustainably managed stocks. Speed optimisation, increased use of less energy-intensive fishing gear and improved engine and fuel technology are technical measures that would considerably decrease resource use and environmental impact caused by fishery. Due to the importance of fishery for the overall results, the most important environmental improvement option after landing is to maintain high quality and minimise product losses. Recommendations and Outlook  The need for good baseline data concerning resource use and marine environmental impact of fisheries in order to perform environmental assessment of seafood products was demonstrated. LCA was shown to be a valuable tool for such assessments, which in the future could be used to improve the environmental performance of the seafood production chain or in the development of criteria of eco-label-ling of seafood products originating in capture fisheries.