Abundance and characteristics of Polychaeta taxa and associated sediment during POLARSTERN campaign ANT-XXII/3 (ANDEEP-IIII)

During the austral summer of 2005, the Weddell deep sea and adjacent basins were sampled in the course of the ANDEEP III project. In this study, 19 epibenthic-sledge stations are analyzed, with a focus on species diversity and distribution patterns of polychaetes. The polychaete fauna of the deep Southern Ocean has been found to be similarly speciose and diverse compared with deep-sea basins worldwide. Also, in depths below 2,000 m many polychaete species do not seem to be endemic for certain areas but are rather far spread within the Southern Ocean and beyond. Therefore, ongoing faunal exchanges between adjacent basins, even beyond the Antarctic convergence, are strongly suggested, ruling out a general isolation of the Southern Ocean deep-sea benthos. Driving forces behind species distribution patterns were investigated. The findings indicate that polychaete species' distribution in the Southern Ocean deep sea is rather dependent on local environment than depths.

Survey bottom trawl data of Micromesistius poutassou (blue whiting) in Bay of Biscay and Celtic Sea from the EVHOE time series (1997-2011)

Data were collected during various groundfish surveys carried out by IFREMER from October to December between 1997 and 2011, on the eastern continental shelf of the Bay of Biscay and in the Celtic Sea (EVHOE series). The sampling design was stratified according to latitude and depth. A 36/47 GOV trawl was used with a 20 mm mesh codend liner. Haul duration was 30 minutes at a towing speed of 4 knots. Fishing was restricted to daylight hours. Catch weights and catch numbers were recorded for all species and body size measured. The weights and numbers per haul were transformed into abundances per km**2 by considering the swept area of a standard haul (0.069 km**2).

Report.

Report year varies.

Vangstatistieken van Hollandsche stoomtrawlers

Overgedrukt uit: "Mededeelingen over visscherij."

Abundance, biomass and secondary production of benthic megafauna on the Barents Sea shelf in 2008 and 2009

Megabenthos plays a major role in the overall energy flow on Arctic shelves, but information on megabenthic secondary production on large spatial scales is scarce. Here, we estimated for the first time megabenthic secondary production for the entire Barents Sea shelf by applying a species-based empirical model to an extensive dataset from the joint Norwegian? Russian ecosystem survey. Spatial patterns and relationships were analyzed within a GIS. The environmental drivers behind the observed production pattern were identified by applying an ordinary least squares regression model. Geographically weighted regression (GWR) was used to examine the varying relationship of secondary production and the environment on a shelfwide scale. Significantly higher megabenthic secondary production was found in the northeastern, seasonally ice-covered regions of the Barents Sea than in the permanently ice-free southwest. The environmental parameters that significantly relate to the observed pattern are bottom temperature and salinity, sea ice cover, new primary production, trawling pressure, and bottom current speed. The GWR proved to be a versatile tool for analyzing the regionally varying relationships of benthic secondary production and its environmental drivers (R² = 0.73). The observed pattern indicates tight pelagic? benthic coupling in the realm of the productive marginal ice zone. Ongoing decrease of winter sea ice extent and the associated poleward movement of the seasonal ice edge point towards a distinct decline of benthic secondary production in the northeastern Barents Sea in the future.

Under-ice fauna, sea-ice concentration, sea-ice thickness and under-ice water parameters from the Eurasian central Arctic Ocean during POLARSTERN cruise ARK-XXVII/3 (PS80) in August-September 2012

Arctic sea-ice decline is expected to have a significant impact on Arctic marine ecosystems. Ice-associated fauna play a key role in this context because they constitute a unique part of Arctic biodiversity and transmit carbon from sea-ice algae into pelagic and benthic food webs. Our study presents the first regional-scale record of under-ice faunal distribution and the environmental characteristics of under-ice habitats throughout the Eurasian Basin. Sampling was conducted with a Surface and Under-Ice Trawl, equipped with a sensor array recording ice thickness and other physical parameters during trawling. We identified 2 environmental regimes, broadly coherent with the Nansen and Amundsen Basins. The Nansen Basin regime was distinguished from the Amundsen Basin regime by heavier sea-ice conditions, higher surface salinities and higher nitrate + nitrite concentrations. We found a diverse (28 species) under-ice community throughout the Eurasian Basin. Change in community structure reflected differences in the relative contribution of abundant species. Copepods (Calanus hyperboreus and C. glacialis) dominated in the Nansen Basin regime. In the Amundsen Basin regime, amphipods (Apherusa glacialis, Themisto libellula) dominated. Polar cod Boreogadus saida was present throughout the sampling area. Abrupt changes from a dominance of ice-associated amphipods at ice-covered stations to a dominance of pelagic amphipods (T. libellula) at nearby ice-free stations emphasised the decisive influence of sea ice on small-scale patterns in the surface-layer community. The observed response in community composition to different environmental regimes indicates potential long-term alterations in Arctic marine ecosystems as the Arctic Ocean continues to change.

Typologie de la flottille chalutière du port de Sète par une méthode de segmentation

This work aims to define a typology of trawler f1eet in Sète, the main fishing harbour along the French Mediterranean coast, using several multivariate analysis methods. The fishing ships taken to account are represented by annual profiles of landing specific compositions. Five fishing strategies have been identified. A segmentation method using symbolic objects allows a formaI characterisation of the different strategies. These strategies are studied according to several general characteristics usually used for management rules elaboration (power, length, ship age). The typological analysis allows to characterise two main exploitation ways, one directed to the catch of a few species (Engraulis encrasicolus, Sardina pilchardus), the other characterised by the exploitation of a great diversity of species. By this way, it is possible to estimate how the catch of low represented species can significantly contribute to the exploitation of a resource.

Fishing gear selectivity for Lates niloticus L., Oreochromis niloticus L. and Rastrineobola argentea P. in Lakes Victoria, Kyoga and Nabugabo

Catch effort data on which fisheries management regulations are sometimes based are not available for most lakes in Uganda. However, failure to regulate fishing gears and methods has been a major cause of collapse of fisheries in the country. Fisheries have been damaged by destructive and non-selective fishing gears and methods such as trawling and beach seining, by use of gill nets of mesh size which crop immature fish and by introduction of mechanised fishing. Selectivity of gears used to crop Lates niloticus L.(Nile perch), Oreochromis niloticus L. (Nile tilapia) and Rastrineobola argentea Pellegrin (Mukene) which are currently the most important commercial species in Uganda were examined in order to recommend the most suitable types, sizes and methods that should be used in exploiting these fisheries. Gill nets of less than 127 mm mainly cropped immature Nile tilapia and Nile perch. To protect these fisheries, the minimum mesh size of gill nets should be set at 127 mm. Seine nets of 5 mm caught high proportions in immature Mukene while those of 10 mm caught mainly mature Mukene. When operated inshore, both sizes caught immature Nile perch and Nile tilapia as by-catch. To protect the Mukene fishery and avoid catching immature bye-catch, a minimum mesh size of the Mukene net should be 10 mm operated as Lampara type net offshore, but since most fishermen have been using 5 mm seine nets for over five years the minimum size should not be allowed to drop below 5 mm pending further thorough investigations. Beach seining and trawling are destructive to fisheries and should be prohibited until data that may justify their use is available.

The Cost of Co-viability in the Australian Northern Prawn Fishery

Fisheries management must address multiple, often conflicting objectives in a highly uncertain context. In particular, while the bio-economic performance of trawl fisheries is subject to high levels of biological and economic uncertainty, the impact of trawling on broader biodiversity is also a major concern for their management. The purpose of this study is to propose an analytical framework to formally assess the trade-offs associated with balancing biological, economic and non-target species conservation objectives. We use the Australian Northern Prawn Fishery (NPF), which is one of the most valuable federally managed commercial fisheries in Australia, as a case study. We develop a stochastic co-viability assessment of the fishery under multiple management objectives. Results show that, due to the variability in the interactions between the fishery and the ecosystem, current management strategies are characterized by biological and economic risks. Results highlight the trade-offs between respecting biological, economic and non-target species conservation constraints at each point in time with a high probability and maximizing the net present value of the fishery.

Threatened by mining, polymetallic nodules are required to preserve abyssal epifauna

Polymetallic nodule mining at abyssal depths in the Clarion Clipperton Fracture Zone (Eastern Central Pacific) will impact one of the most remote and least known environments on Earth. Since vast areas are being targeted by concession holders for future mining, large-scale effects of these activities are expected. Hence, insight into the fauna associated with nodules is crucial to support effective environmental management. In this study video surveys were used to compare the epifauna from sites with contrasting nodule coverage in four license areas. Results showed that epifaunal densities are more than two times higher at dense nodule coverage (>25 versus ≤10 individuals per 100 m2), and that taxa such as alcyonacean and antipatharian corals are virtually absent from nodule-free areas. Furthermore, surveys conducted along tracks from trawling or experimental mining simulations up to 37 years old, suggest that the removal of epifauna is almost complete and that its full recovery is slow. By highlighting the importance of nodules for the epifaunal biodiversity of this abyssal area, we urge for cautious consideration of the criteria for determining future preservation zones.

Oyster (Ostrea edulis) extirpation and ecosystem transformation in the Firth of Forth, Scotland

Marine inshore communities, including biogenic habitats have undergone dramatic changes as a result of exploitation, pollution, land-use changes and introduced species. The Firth of Forth on the east coast of Scotland was once home to the most important oyster (Ostrea edulis Linnaeus, 1758) beds in Scotland. 19th and early 20th century fisheries scientists documented the degradation and loss of these beds, yet transformation of the wider benthic community has been little studied. We undertook archival searches, ecological surveys and shell community analysis using radioisotope dated sediment cores to investigate the history of decline of Forth oyster beds over the last 200 years and the changes to its wider biological communities. Quadrat analysis of the present day benthos reveal that soft-sediment communities dominate the Firth of Forth, with little remaining evidence of past oyster beds in places where abundant shell remains were picked up by a survey undertaken in 1895. Queen scallops (Aequipecten opercularis Linnaeus, 1758) and horse mussels (Modiolus modiolus Linnaeus, 1758) were once common within the Forth but have also markedly decreased compared to the earlier survey. Ouranalyses of shell remains suggest that overall mollusc biomass and species richness declined throughout the 19th century and early 20th century, suggesting broader-scale community change as human impacts increased and as habitats degraded. Inshore communities in the Firth of Forth today are less productive and less diverse compared to past states, with evidence suggesting that most of the damage was done by early bottom trawling and dredging activities. Given the pervasive nature of intensive trawling over the past 150 years, the kind of degradation we document for the Firth of Forth is likely to be commonplace within UK inshore communities.

A comparative study of the species composition of discards from five fisheries from the Algarve (southern Portugal)

Discards from five of the most important fisheries (crustacean trawling, fish trawling, demersal purse seining, pelagic purse seining and trammel netting) in southern Portugal were studied and compared. A total of 236 species of all taxa were discarded, with fish and cephalopods accounting for more than 90% of the discarded biomass, except trammel nets (81%). Although there was some overlapping of species, multivariate analysis using cluster analysis for classification and multidimensional scaling (MDS) for ordination, showed that there were significant differences between the five gears in terms of species composition and biomasses discarded, with the least similarity between crustacean trawling and all other fishing operations. The differences between fisheries were probably as a result of a combination of gear selectivity and depth fished. The results suggest that discarding practices are likely to have different, yet significant impacts on the marine ecosystem, warranting further studies on the fate of discards, the factors influencing discarding and mitigation.

Size selectivity of diamond and square mesh cod ends for four by-catch species in the crustacean fishery off the Portuguese south coast

The effects of an increase in cod end mesh size from 55 to 60 and 70 mm and a change of mesh configuration from 55 mm diamond to 55 turn square mesh on the size selectivity of four by-catch species (the red shrimp Aristeus antennatus, the European hake Merluccius merluccius, the horse mackerel Trachurus trachurus and the blue whiting Micromesistius poutassou) commonly captured in the crustacean fishery off the Portuguese south coast, were evaluated. Selectivity parameters for blue whiting, the most abundant species in the catches, were estimated taking into account between-haul variation, while for the remaining species, captured in much lower quantities, the selectivity estimates were based on pooled data by length class for all hauls within the same cod end. Length at 50% retention, L-50, was found to increase with mesh size and with the change in mesh configuration for all the studied species. For blue whiting trawling depth and cod end catch were found to play a role in between-haul variation by increasing L-50 as well. The results suggest that an increase in the current minimum mesh size of 55-70 mm would be advisable to be compatible with the minimum landing sizes (MLSs) of 29 mm carapace length and 27 cm total length for red shrimp and hake, respectively, while it would greatly reduce the amount of discards, particularly those for blue whiting, that accounted for approximately 50% of the total catch weight. Horse mackerel was the only species for which the use of a larger mesh size would result in a significant escapement of individuals above the MLS of 15 cm. (C) 2002 Elsevier Science B.V. All rights reserved.

Size selectivity of diamond and square mesh cod ends for rose shrimp (Parapenaeus longirostris) and Norway lobster (Nephrops norvegicus) off the Portuguese south coast

The effects of an increase in cod end mesh size from 55 to 60 and 70 mm and a change of mesh configuration from diamond to square mesh on the size selectivity for rose shrimp Parapenaeus longirostris and Norway lobster Nephrops norvegicus captured off the Portuguese south coast were evaluated. The results were analysed taking into account between-haul variation in selectivity, and indicate a significant increase in L-50 for rose shrimp with an increase in mesh size or with the use of a square mesh cod end, while for Norway lobster only mesh configuration was found to affect this parameter. Two other important external variables were identified; the trawling depth and the cod end catch, which influence between-haul variation, by increasing the selection range for rose shrimp and Norway lobster, respectively. The results obtained suggest that an increase in the current minimum mesh size of 55 mm would be advisable for rose shrimp in order to respect the minimum landing size of 24 mm carapace length presently established for this species. Moreover, trawling for rose shrimp should be avoided at depths above 200 m, in order to avoid catches consisting almost exclusively of juveniles. Such an increase in mesh size would have a minor impact in terms of losses of individuals above the minimum landing size for Norway lobster and would contribute to reducing the amount of discards in this fishery. (C) 2002 Elsevier Science B.V. All rights reserved.