Deep-sea trawling off the Portuguese continental coast––Spatial patterns, target species and impact of a prospective EU-level ban

Abstract Faraj, A., and Bez, N. 2007. Spatial considerations for the Dakhla stock of Octopus vulgaris: indicators, patterns, and fisheries interactions. – ICES Journal of Marine Science, 64: 1820–1828. The common octopus (Octopus vulgaris) is the target species of the cephalopod fishery that exploits two stocks, Dakhla and Cap Blanc, off southern Morocco (26°N 21°N), an area commonly referred to as the Saharan Bank. Octopusvulgaris is also one of the most abundant demersal species in this highly productive area, and plays a key role in the upwelling ecosystem. Spatial patterns of the main phases of the Octopus vulgaris life cycle of the Dakhla stock are described, using trawl surveys carried out twice a year from 1998 to 2003. Using geostatistics and spatial indicators, mature females and juveniles are analysed and mapped to characterize the main features of the spawning and recruitment phases. There are clear distinctions between the spatial patterns of the spawning and recruitment phases: juveniles are more coastal, less spatially dispersed, more anisotropically distributed, and more patchy. Our results suggest that the spatial pattern of the Octopus vulgaris Dakhla stock is different from that of the same species in other ecosystems such as the Mediterranean. GIS reveals that the spawning–stock biomass is globally more accessible to the industrial fleet than to the artisanal one, a finding contrary to contemporary thinking and with important resource management implications.

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Fine-Scale Heterogeneity of a Cold-Water Coral Reef and Its Influence on the Distribution of Associated Taxa

Frontiers in Marine Science ◽

10.3389/fmars.2021.556313 ◽

2021 ◽

Vol 8 ◽

Author(s):

David M. Price ◽

Aaron Lim ◽

Alexander Callaway ◽

Markus P. Eichhorn ◽

Andrew J. Wheeler ◽

...

Keyword(s):

Spatial Patterns ◽

Deep Sea ◽

Cold Water ◽

Biological Effects ◽

Pair Correlation ◽

Growth Patterns ◽

Environmental Drivers ◽

Point Pattern ◽

Fine Scale ◽

Water Coral

Benthic fauna form spatial patterns which are the result of both biotic and abiotic processes, which can be quantified with a range of landscape ecology descriptors. Fine- to medium-scale spatial patterns (<1–10 m) have seldom been quantified in deep-sea habitats, but can provide fundamental ecological insights into species’ niches and interactions. Cold-water coral reefs formed by Desmophyllum pertusum (syn. Lophelia pertusa) and Madrepora oculata are traditionally mapped and surveyed with multibeam echosounders and video transects, which limit the ability to achieve the resolution and/or coverage to undertake fine-scale, centimetric quantification of spatial patterns. However, photomosaics constructed from imagery collected with remotely operated vehicles (ROVs) are becoming a prevalent research tool and can reveal novel information at the scale of individual coral colonies. A survey using a downward facing camera mounted on a ROV traversed the Piddington Mound (Belgica Mound Province, NE Atlantic) in a lawnmower pattern in order to create 3D reconstructions of the reef with Structure-from-Motion techniques. Three high resolution orthorectified photomosaics and digital elevation models (DEM) >200 m2 were created and all organisms were geotagged in order to illustrate their point pattern. The pair correlation function was used to establish whether organisms demonstrated a clustered pattern (CP) at various scales. We further applied a point pattern modelling approach to identify four potential point patterns: complete spatial randomness (CSR), an inhomogeneous pattern influenced by environmental drivers, random clustered point pattern indicating biologically driven clustering and an inhomogeneous clustered point pattern driven by a combination of environmental drivers and biological effects. Reef framework presence and structural complexity determined inhabitant distribution with most organisms showing a departure from CSR. These CPs are likely caused by an affinity to local environmental drivers, growth patterns and restricted dispersion reproductive strategies within the habitat across a range of fine to medium scales. These data provide novel and detailed insights into fine-scale habitat heterogeneity, showing that non-random distributions are apparent and detectable at these fine scales in deep-sea habitats.

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Seasonality in the deep sea and tropics revisited: what can otoliths tell us?

Marine and Freshwater Research ◽

10.1071/mf04150 ◽

2005 ◽

Vol 56 (5) ◽

pp. 585 ◽

Cited By ~ 43

Author(s):

Beatriz Morales-Nin ◽

Jacques Panfili

Keyword(s):

Deep Sea ◽

Fishery Management ◽

Seasonal Fluctuation ◽

Aquatic Environments ◽

Target Species ◽

Otolith Growth ◽

Climatic Fluctuations ◽

Tropical Regions ◽

Growth Increments ◽

Almost All

The accepted idea that fish otoliths from supposedly aseasonal environments, such as the deep sea and tropics, do not present seasonal growth increments is questioned and re-evaluated. The main seasonal fluctuation in deep seas is a result of the transfer of organic material from the productive upper layers to the abyssal depths. There is some evidence for seasonal patterns of otolith growth, although the validation of seasonal structures is limited owing to the difficulties inherent in deep-water studies. Tropical regions have an extremely high diversity of aquatic environments but in fact very few are aseasonal, and almost all areas have strong hydrological seasons, mainly annual, interacting with temperature variations. These climatic fluctuations have undoubtedly an effect on otolith growth, therefore leading to a succession of different incremental zones. The lack of previous knowledge on this impact of seasonality is probably a result of the previous low level of exploitation or economic interest of target species, and consequently the absence of age-based assessments. This trend has now changed possibly as a result of the increased exploitation of the resources, and to the greater involvement of international and national fishery management bodies. The number of studies showing apparent or validated seasonal marks has recently increased for these environments.

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Net winch design in trawlers, influence of vessel size and fishing ground

Proceedings of the Institution of Mechanical Engineers Part M Journal of Engineering for the Maritime Environment ◽

10.1177/1475090217718923 ◽

2017 ◽

Vol 233 (1) ◽

pp. 108-123 ◽

Cited By ~ 1

Author(s):

Luis Carral Couce ◽

Juan Carral Couce ◽

Javier Tarrío-Saavedra ◽

José A Fraguela Formoso

Keyword(s):

Deep Sea ◽

Fishing Ground ◽

Design Parameters ◽

Target Species ◽

Auxiliary Equipment ◽

Vessel Size ◽

Fishing Fleet ◽

Operation Speed

With mid-depth trawling techniques, the number of fishing grounds available increases. In turn, the vessel can have a greater workload, as it has to control and direct its activity towards different species depending on the use of mid- or deep-sea equipment. However, specific equipment for each depth has to be used and this equipment influences the fishing manoeuvre. A new piece of auxiliary equipment comes into play to haul and store the net: the net winch. The aim of this study is to determine the most suitable net winch for each of the various vessels, fishing grounds and fishing modalities of the Spanish trawling fishing fleet. For each fishing ground, vessel size and target species, a relationship will be established with the net winch design parameters: fishing reel capacity, traction and operation speed.

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The deep-sea red crab Chaceon notialis (Geryonidae) in the southwestern Atlantic Ocean: Spatial patterns and long-term effects of fishing

Fisheries Research ◽

10.1016/j.fishres.2016.06.016 ◽

2016 ◽

Vol 183 ◽

pp. 254-262 ◽

Cited By ~ 4

Author(s):

Arianna Masello ◽

Omar Defeo

Keyword(s):

Atlantic Ocean ◽

Spatial Patterns ◽

Deep Sea ◽

Southwestern Atlantic ◽

Long Term Effects ◽

Southwestern Atlantic Ocean

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Spatial patterns of Aquificales in deep-sea vents along the Eastern Lau Spreading Center (SW Pacific)

Systematic and Applied Microbiology ◽

10.1016/j.syapm.2014.04.002 ◽

2014 ◽

Vol 37 (6) ◽

pp. 442-448 ◽

Cited By ~ 7

Author(s):

Isabel Ferrera ◽

Amy B. Banta ◽

Anna-Louise Reysenbach

Keyword(s):

Spatial Patterns ◽

Deep Sea ◽

Spreading Center ◽

Sw Pacific

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An assessment of environmental metabarcoding protocols aiming at favouring contemporary biodiversity in inventories of deep-sea communities

10.1101/836080 ◽

2019 ◽

Author(s):

Miriam I. Brandt ◽

Blandine Trouche ◽

Nicolas Henry ◽

Cathy Liautard-Haag ◽

Lois Maignien ◽

...

Keyword(s):

Spatial Patterns ◽

Ancient Dna ◽

Deep Sea ◽

Messenger Rna ◽

Environmental Dna ◽

List Type ◽

Dna Fragments ◽

Large Reservoir ◽

Alpha And Beta Diversity ◽

Dna And Rna

ABSTRACTThe abyssal seafloor covers more than 50% of planet Earth and is a large reservoir of still mostly undescribed biodiversity. It is increasingly under target of resource-extraction industries although being drastically understudied. In such remote and hard-to-access ecosystems, environmental DNA (eDNA) metabarcoding is a useful and efficient tool for studying biodiversity and implementing environmental impact assessments. Yet, eDNA analysis outcomes may be biased towards describing past rather than present communities as sediments contain both contemporary and ancient DNA.Using commercially available kits, we investigated the impacts of five molecular processing methods on DNA metabarcoding biodiversity inventories targeting prokaryotes (16S-V4V5), unicellular eukaryotes (18S-V4), and metazoans (18S-V1, COI). As the size distribution of ancient DNA is skewed towards small fragments, we evaluated the effect of removing short DNA fragments via size-selection and ethanol reconcentration using DNA extracted from 10 g of sediment at five deep-sea sites. We also compare communities revealed by DNA and RNA co-extracted from 2 g of sediment at the same sites.Results show that removing short DNA fragments does not affect alpha and beta diversity estimates in any of the biological compartments investigated. Results also confirm doubts regarding the possibility to better describe live communities using environmental RNA (eRNA). With ribosomal loci, RNA, while resolving similar spatial patterns than co-extracted DNA, resulted in significantly higher richness estimates, supporting hypotheses of increased persistence of ribosomal RNA (rRNA) in the environment and unmeasured bias due to over-abundance of rRNA and RNA release. With the mitochondrial locus, RNA detected lower metazoan richness and resolved less spatial patterns than co-extracted DNA, reflecting high messenger RNA lability. Results also highlight the importance of using large amounts of sediment (≥10 g) for accurately surveying eukaryotic diversity.We conclude that DNA should be favoured over RNA for logistically realistic, repeatable, and reliable surveys, and confirm that large sediment samples (≥10 g) deliver more complete and accurate assessments of benthic eukaryotic biodiversity and that increasing the number of biological rather than technical replicates is important to infer robust ecological patterns.

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