Article

Disturbance of the Seabed by Mobile Fishing Gear: A Comparison to Forest Clearcutting

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Abstract

Bottom trawling and use of other mobile fishing gear have effects on the seabed that resemble forest clearcutting, a terrestrial disturbance recognized as a major threat to biological diversity and economic sustainability. Structures in marine benthic communities are generally much smaller than those in forests, but structural complexity is no less important to their biodiversity. Use of mobile fishing gear crushes, buries, and exposes marine animals and structures on and in the substratum, sharply reducing structural diversity. Its severity is roughly comparable to other natural and anthropogenic marine disturbances. It also alters biogeochemical cycles, perhaps even globally. Recovery after disturbance is often slow because recruitment is patchy and growth to maturity takes years, decades, or more for some structure-forming species. Trawling and dredging are especially problematic where the return interval—the time from one dredging or trawling event to the next—is shorter than the time it takes for the ecosystem to recover; extensive areas can be trawled 100–700% per year or more. The effects of mobile fishing gear on biodiversity are most severe where natural disturbance is least prevalent, particularly on the outer continental shelf and slope, where storm-wave damage is negligible and biological processes, including growth, tend to be slow. Recent advances in fishing technology (e.g., rockhopper gear, global positioning systems, fish finders) have all but eliminated what were de facto refuges from trawling. The frequency of trawling (in percentage of the continental shelf trawled per year) is orders of magnitude higher than other severe seabed disturbances, annually covering an area equivalent to perhaps half of the world’s continental shelf, or 150 times the land area that is clearcut yearly. Mobile fishing gear can have large and long-lasting effects on benthic communities, including young stages of commercially important fishes, although some species benefit when structural complexity is reduced. These findings are crucial for implementation of “Essential Fish Habitat” provisions of the U.S. Magnuson-Stevens Fishery Conservation and Management Act which aim to protect nursery and feeding habitat for commercial fishes. Using a precautionary approach to management, modifying fishing methods, and creating refuges free of mobile fishing gear are ways to reduce effects on biological diversity and commercial fish habitat. Perturbaciones del Lecho Marino por Artes de Pesca Móbiles: Una Comparación con la Tala Forestals Los arrastres de fondo y el uso de otras artes de pesca móviles tienen efectos en el lecho marino que se asemejan a la tala total de bosques, que es a su vez una pertubación terrestre reconocida como una de las mayores amenazas a la diversidad biológica y la sustentabilidad económica. Las estructuras en comunidades marinas bénticas son generalmente mucho más pequeñas que aquellas en los bosques, pero la complejidad estructural no es menos importante que la biodiversidad. El uso de artes de pesca móviles quiebra, sepulta y expone animales marinos y estructuras sobre y en el substrato, reduciendo marcadamente la diversidad estructural. Su severidad es burdamente comparable con otras perturbaciones marinas de orden natural o antropogénico. Tambien altera los ciclos biogeoquímicos, de hecho a nivel mundial. La recuperación después de una pertubación es frecuentemente lenta debido a que el reclutamiento es por parches y el crecimiento para alcanzar la madurez toma años, décadas o aún más para algunas especies que forman estructuras. Los arrastres de fondo y dragados son especialmente problemáticos donde el intervalo de retorno (tiempo entre un evento de dragado o arrastre y otro) es más corto que el tiempo que toma a un ecosistema recuperarse;árears extensas son arrastradas entre un 100 y 700% por año o mas. Los efectos de las artes de pesca móviles en la biodiversidad son más severos cuando las perturbaciones naturales son menos prevalentes, particularmente en las afueras de la plataforma continental y la pendiente, donde el daño del oleaje por tormentas es negligible y los procesos biológicos (incluyendo crecimiento) tienden a ser lentos. Recientes avances en tecnología pesquera (e.g., sistemas de posicionamiento global, detectores de peces) aparentemente tienen todo, pero eliminan lo que de facto fueran refugios contra arrastres. La frecuencia de los arrastres (en porcentaje de la plataforma continental arrastrada por año) es órdenes de magnitud mayor que otras perturbaciones severas al lecho marino, anualmente la cobertura de área es equivalente quizá a la mitad de la plataforma continental marina, o 150 veces el área de tierra que es talada anualmente. Las artes de pesca móviles pueden tener impactos grandes y de larga duración en las comunidades bentónicas, incluyendo estadios jóvenes de peces de importancia comercial, aunque algunas especies se benefician cuando la complejidad estructural es reducida. Estos descubrimientos son cruciales para la implementación de el “hábitat esencial para peces” del Acta de Conservación y Manejo de Pesquerias Magnuson-Stevens de los Estados Unidos y que pretende establecer hábitats de reproducción y alimentación para peces comerciales. El uso de una aproximación precautoria de manejo, la modificación de métodos de pesca y la creación de refugios libres de artes de pesca móviles son formas para reducir los efectos en la diversidad biológica y el hábitat para peces comerciales.

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... The presence of upright benthic fauna in areas closed to bottom-towed gear likely contribute to structural complexity and habitat heterogeneity [21,37,52,54], that may provide for increasing community diversity over time. ...
... Communities on mixed substrata are likely specifically vulnerable to impacts from bottom-towed gear [55]. Recovery of community assemblages will be dependent on growth of surviving biota, species' life-history factors and specific habitat requirements [27,54,56]. Species with high dispersal potential, short lifespans and less habitat-specific requirements, such as polychaetes, will have short recovery timescales (< 3 years) [55,56]. ...
... In contrast, recovery of longer-lived, slow-growing habitat-specific species (e.g. pink sea fan, ross coral) may take decades (> 20 years) [53][54][55][56]. It is possible that recovery of some species previously found on circalittoral coarse sediments may be hampered by lack of recruitment. ...
Article
The global marine environment has seen recent rapid growth in Marine Protected Areas (MPAs). In UK (English) waters, MPAs incorporate Special Protection Areas (SPAs), Special Areas of Conservation (SACs) and Marine Conservation Zones (MCZs), each with specific conservation objectives. In accordance with legislation, the UK has adopted a feature-based approach to MPA designation and monitoring, whereby protection of listed species and habitats are prioritised. The Eddystone Reef (part of the Start Point to Plymouth Sound and Eddystone SAC, South West UK) is designated solely for its reef features. The reef is at high risk from fisheries, particularly bottom-towed fishing gear. On 1st of January 2014 bottom-towed fisheries were prohibited within designated areas of the reef. In this study, images from drop-down camera surveys were analysed to quantitatively assess patterns in diversity and abundance of benthic fauna on reef and mixed substratum habitats that are closed, and remain open, to bottom-towed fisheries. Coarse sediments in areas closed to bottom-towed gear supported a greater abundance of sessile, upright, slow growing species (e.g. pink sea fans, ross coral, branching sponges) than were present in areas still actively towed over. Coarse sediments open to bottom-towed gear had greater abundances of motile, scavenging or opportunistic species. This study highlights the potential for positive conservation benefits beyond the traditional feature-based approach to MPA designation and monitoring. Further conservation gains could be made by reducing fragmentation of protected habitats and by increasing area coverage of statutory controls on bottom-towed fishing in already designated MPAs.
... Although trawling sometimes occurs in midwater column or the pelagic zone, most trawling occurs along the seafloor. This "bottom trawling" (or "dragging") targets demersal or benthic organisms such as groundfish (e.g., cod, plaice, orange roughy), scallops, clams, shrimp, and sea urchins (25). ...
... Another method is the beam trawl, in which a large, cone-shaped net is held open by a horizontal beam rather than otter boards (25). These contraptions are often equipped with 'tickler chains' meant to disturb fish and other organisms from the seabed (24). ...
... Typically, beam trawls are utilized in waters shallower than otter trawls, at depths of only a couple hundred meters (28). Consequently, these nets are typically smaller than those of otter trawls with widths reaching up to 12m (25). ...
Preprint
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The deep-sea is the largest continuous ecosystem on Earth, yet it remains one of the least understood by scientists. Exploitation of the deep-sea takes several forms including commercial fishing and, in the near future, mining. Bottom trawling is a destructive, nonselective fishing method that is well established all over the world. Consequently, its environmental impacts have been well studied. Deep-sea mining (DSM), on the other hand, has not yet begun commercially, but is expected to commence in both national and international waters within the next few decades. Since no large-scale seabed mining has yet taken place, its environmental impacts remain uncertain. This thesis explores the similarities of bathyal deep-sea bottom trawling (DSBT) and abyssal DSM to determine if the well-known environmental impacts of DSBT can be used to predict those of DSM. Methodologies are compared, as well as the biotic and faunal aspects of their respective benthic ecosystems. It is likely that the environmental effects of DSBT can and should be used in assessing the impacts of DSM. Because full-scale in situ testing remains challenging and expensive for submarine mining, this insight may prove helpful in establishing preliminary regulations and environmental protections for DSM.
... increased turbidity; displacement of glacial dropstones or boulders; and seafloor homogenisation (Watling and Norse, 1998, Thrush and Dayton, 2002, Pusceddu et al., 2014. Benthic faunal impacts include: removal or in-situ mortality; smothering; displacement; and structural damage to biogenic habitat (e.g. ...
... Benthic faunal impacts include: removal or in-situ mortality; smothering; displacement; and structural damage to biogenic habitat (e.g. cold-water coral reefs); and alteration of trophic structures where disturbance differentially impacts different species (for example negative impacting long-lived sessile species with low resilience to disturbance whilst promoting mobile scavengers and opportunistic species) (Watling and Norse, 1998, Koslow et al., 2000, Gage et al., 2005, Hall-Spencer et al., 2007. ...
... The inherent vulnerability of deep-sea fauna, heavy gear, and high bycatch rates have led to the sustainability of deep-sea fisheries being questioned from a benthic ecosystem perspective. Deepsea demersal trawling has been likened to ploughing (Puig et al., 2012) and clear-cutting forests (Watling and Norse, 1998), in terms of the considerable ecosystem impacts. The longevity of these impacts is likely to be significant with recovery estimated to take decades, centuries or even longer, particularly in the case of VMEs (Roberts, 2002). ...
Thesis
The deep sea (>200 m) is the world’s least explored and largest biome, covering ~65% of the earth’s surface, it is increasingly subject to anthropogenic disturbance from fishing. The offshore Greenland halibut (Reinhardtius hippoglossoides) fishery, west Greenland, employs demersal trawl gear at depths of 800-1,400 m. Recent Marine Stewardship Council (MSC) certification of this fishery highlighted the paucity of knowledge of benthic habitats and trawling impacts. This interdisciplinary thesis employs a benthic video sled to investigate deep-sea habitats and trawling impacts and conducts a critical analysis of the fishery’s governance, with reference to the role of the MSC certification. The results provide new insights into this poorly known region of the Northwest Atlantic, including identifying four candidate vulnerable marine ecosystems (VMEs). Imagery obtained demonstrates that chronic trawling has had extensive impacts on the seafloor, which are significantly associated with the benthic communities observed. Further, trawling effort is shown to have a significant negative association with the abundance of some VME indicator taxa. The governance case study finds an effective system of state-led governance, supported by scientific, certification and industry actors. Outcomes directly attributable to engagement with the MSC certification include the introduction of a management plan and new benthic research programmes. However, questions are raised about the MSC certification, providing case study examples of existing criticisms. Assessments are weak with respect to benthic habitats and overreliant on the definitive, expert judgement of Conformity Assessment Bodies (CABs), whose independence is questioned. The assurance offered by the MSC certification in terms of the sustainability of trawling impacts on benthic ecosystems is found to seriously lack credibility. Findings are of direct relevance to the management of deep-sea fisheries in Greenland and elsewhere. Widely applicable critical insights into deep-sea fishery governance are presented, including into the role of eco-labels as a market-mechanism to promote sustainable fishery management.
... Deep-sea fisheries predominantly employ demersal otter trawls, in which the depth necessitates heavy gear with trawl doors weighing 2-5 tonnes each and sometimes more (Roberts, 2002;Clark and Koslow, 2007;Clark et al., 2016). The ecosystem effects of these gears have been likened to clear cutting of forests (Watling and Norse, 1998) and ploughing of agricultural land (Puig et al., 2012). The effects of trawl gear on the seabed include mixing of sediments; physical trawl scars or tracks; increased turbidity; displacement of glacial dropstones or boulders; and seafloor homogenization (Watling and Norse, 1998;Thrush and Dayton, 2002;Pusceddu et al., 2014). ...
... The ecosystem effects of these gears have been likened to clear cutting of forests (Watling and Norse, 1998) and ploughing of agricultural land (Puig et al., 2012). The effects of trawl gear on the seabed include mixing of sediments; physical trawl scars or tracks; increased turbidity; displacement of glacial dropstones or boulders; and seafloor homogenization (Watling and Norse, 1998;Thrush and Dayton, 2002;Pusceddu et al., 2014). Benthic faunal impacts include removal or in-situ mortality; smothering; displacement; and structural damage to biogenic habitat (e.g. ...
Article
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The offshore Greenland halibut (Reinhardtius hippoglossoides) fishery, west Greenland, employs demersal trawl gear at depths of 800–1400 m. In contrast to many deep-sea fisheries, the target stock appears stable and the fishery is of significant economic importance. Recent Marine Stewardship Council certification of this fishery highlighted the paucity of knowledge of benthic habitats and trawling impacts, which this study aimed to address using a towed benthic video sled. The spatially discrete northern and southern areas of the fishery were found to be distinct in terms of the communities present, which non-metric multidimensional scaling suggests is primarily driven by temperature. Extensive physical evidence of trawling was observed. Trawling effort was significantly linked with community composition, with a negative association between trawling effort and abundance of some taxa, including some vulnerable marine ecosystem (VME) indicator species. Three potential VMEs are identified: (i) Flabellum alabastrum cup coral meadows; (ii) a Halipteris finmarchica sea pen field; and (iii) areas exhibiting mixed assemblages of VME indicators. Of immediate conservation concern is a H. finmarchica field, which seems to be at least regionally rare, is situated within the fringes of existing trawling effort and is currently afforded no protection by management measures.
... Every type of fishing gear that interacts with the benthos, to some extent, can damage essential fish habitat (EFH) crucial to the reproduction, development, and protection of fish species (Grieve et al. 2014;Grieve et al. 2015). Impacts to EFH by fishing gear range from changes to sediment habitats as well as the damage and/or loss of emergent epiflora (Bridger 1972;Peterson et al. 1983;Currie and Parry 1996;Watling and Norse 1998;Watling et al. 2001). Such impacts by fishing gear can also greatly reduce benthic structural diversity and alter population productivity (Dayton et al. 1995;Watling and Norse 1998). ...
... Impacts to EFH by fishing gear range from changes to sediment habitats as well as the damage and/or loss of emergent epiflora (Bridger 1972;Peterson et al. 1983;Currie and Parry 1996;Watling and Norse 1998;Watling et al. 2001). Such impacts by fishing gear can also greatly reduce benthic structural diversity and alter population productivity (Dayton et al. 1995;Watling and Norse 1998). Therefore, the increase in fishing effort by the GoM lobster fishery may be inadvertently increasing degradation of EFH. ...
Article
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The Gulf of Maine has been fundamentally altered by anthropogenic forcings for decades and offers an ideal study system to monitor response to change. Through complex interactions between ocean warming, altered demographic bottlenecks, and reduced top-down controls, the American lobster (Homarus americanus Milne Edwards) capitalized on favorable conditions and proliferated within the Gulf of Maine. These changes catalyzed the expansion of the lobster fishery, elevated its status as North America’s most valuable marine resource, and shifted coastal communities towards a virtual lobster monoculture. The same processes that facilitated lobster to capitalize on favorable conditions may come with unintended consequences and have implications for sustainability in a continually changing ocean environment. As such, evaluating the anthropogenic impacts by the American lobster fishery and to lobster demographic processes is critical for effective fisheries management. This dissertation research developed, and implemented, several modeling frameworks to assess how anthropogenic impacts have fundamentally altered the American lobster fishery, how ocean change affects the demographic processes of larval and postlarval lobster, and the implications of these relationships to the sustainability of this species under climate change.
... Every type of fishing gear that interacts with the benthos, to some extent, can damage essential fish habitat (EFH) crucial to the reproduction, development, and protection of fish species (Grieve et al. 2014;Grieve et al. 2015). Impacts to EFH by fishing gear range from changes to sediment habitats as well as the damage and/or loss of emergent epiflora (Bridger 1972;Peterson et al. 1983;Currie and Parry 1996;Watling and Norse 1998;Watling et al. 2001). Such impacts by fishing gear can also greatly reduce benthic structural diversity and alter population productivity (Dayton et al. 1995;Watling and Norse 1998). ...
... Impacts to EFH by fishing gear range from changes to sediment habitats as well as the damage and/or loss of emergent epiflora (Bridger 1972;Peterson et al. 1983;Currie and Parry 1996;Watling and Norse 1998;Watling et al. 2001). Such impacts by fishing gear can also greatly reduce benthic structural diversity and alter population productivity (Dayton et al. 1995;Watling and Norse 1998). Therefore, the increase in fishing effort by the GoM lobster fishery may be inadvertently increasing degradation of EFH. ...
Thesis
Full-text available
The Gulf of Maine has been fundamentally altered by anthropogenic forcings for decades and offers an ideal study system to monitor response to change. Through complex interactions between ocean warming, altered demographic bottlenecks, and reduced top-down controls, the American lobster (Homarus americanus Milne Edwards) capitalized on favorable conditions and proliferated within the Gulf of Maine. These changes catalyzed the expansion of the lobster fishery, elevated its status as North America’s most valuable marine resource, and shifted coastal communities towards a virtual lobster monoculture. The same processes that facilitated lobster to capitalize on favorable conditions may come with unintended consequences and have implications for sustainability in a continually changing ocean environment. As such, evaluating the anthropogenic impacts by the American lobster fishery and to lobster demographic processes is critical for effective fisheries management. This dissertation research developed, and implemented, several modeling frameworks to assess how anthropogenic impacts have fundamentally altered the American lobster fishery, how ocean change affects the demographic processes of larval and postlarval lobster, and the implications of these relationships to the sustainability of this species under climate change.
... Together with the bottom shear stress induced by both waves and bottom currents, bottom trawling is contributing to control sediment resuspension in coastal areas [13][14][15][16][17][18][19][20]. As such, it can deeply affect surface sediments, benthic macrofauna and bioturbation [13,[21][22][23][24]. RiOMar mud fields are organically enriched as compared to surrounding sediments and often constitute preferential fishing areas [19,20]. ...
... Together with the bottom shear stress induced by both waves and bottom currents, bottom trawling is contributing to control sediment resuspension in coastal areas [13][14][15][16][17][18][19][20]. As such, it can deeply affect surface sediments, benthic macrofauna and bioturbation [13,[21][22][23][24]. RiOMar mud fields are organically enriched as compared to surrounding sediments and often constitute preferential fishing areas [19,20]. ...
Article
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The spatial distributions of (1) surface sediment characteristics (D0.5, Sediment Surface Area (SSA), Particulate Organic Carbon (POC), Chlorophyll-a (Chl-a), Phaeophytin-a (Phaeo-a), Total and Enzymatically Hydrolyzable Amino Acids (THAA, EHAA), δ13C) and (2) sediment profile image (apparent Redox Potential Discontinuity (aRPD), numbers and depths of biological traces) characteristics were quantified based on the sampling of 32 stations located within the West Gironde Mud Patch (Bay of Biscay, NE Atlantic) in view of (1) assessing the spatial structuration of a temperate river-dominated ocean margin located in a high-energy area, (2) disentangling the impacts of hydrodynamics and bottom trawling on this structuration, and (3) comparing the West Gironde Mud Patch with the Rhône River Prodelta (located in a low-energy area). Results support the subdivision of the West Gironde Mud Patch in a proximal and a distal part and show (1) the existence of depth gradients in surface sedimentary organics characteristics and bioturbation within the distal part; (2) no evidence for a significant effect of bottom trawling, as opposed to Bottom Shear Stress, on the West Gironde Mud Patch spatial structuration; and (3) major discrepancies between spatial structuration in the West Gironde Mud Patch and the Rhône River Prodelta, which were attributed to differences in tidal regimes, sedimentation processes, and local hydrodynamics, which is in agreement with current river-dominated ocean margin typologies.
... Fishing impacts on coral reefs and marine biodiversity especially concern habitat damage and bycatch issues (Jennings and Polunin, 1996;Chuenpagdee et al., 2003). Physical damage of coral reefs due to fishing activities has been reported for the gears that reach the seafloor, particularly traps and pots (Van Der Knaap, 1993;Stephenson et al., 2017), bottom trawlers and dredges (Watling and Norse, 1998;Pitcher et al., 2000). Sediment generated from fishing operations can affect coral growth and cause mortality due to suffocation and reduction in light penetration (Erftemeijer et al., 2012). ...
... Anthropogenic impact on the oceans shows strong spatial heterogeneity and is mostly concentrated on continental shelves and slope areas (Halpern et al., 2008). In fact, half of the world's continental shelves are continuously being affected by fishing activities, especially bottom trawling (Messieh et al., 1991;Watling and Norse, 1998). Fishing practices directly damage benthic fauna, mainly engineering species (sensu Jones et al., 1994) such as corals, gorgonians and sponges (Fosså et al., 2002;MacDonald et al., 1996;Reed, 2002;Rossi et al., 2017;. ...
Article
Cold-water gorgonians dwelling on the continental shelf are a common by-catch of bottom-contact fishing practices. Given the slow growth and limited recruitment of cold-water gorgonians, the impact of fishing activities may seriously compromise the conservation of the highly complex coral gardens communities. For this reason, the development of effective active and passive restoration methods is nowadays a priority in order to enhance the natural recovery of impacted cold-water coral gardens. However, the ecological restoration of mesophotic and deep-sea communities remains extremely limited, due to its technological requirements and associated costs, which bring its wide-scale and long-term application into question. This study reports the preliminary results of the first large-scale active restoration of more than 400 cold-water gorgonians on the Mediterranean continental shelf. By actively involving local fishers during two consecutive fishing seasons, by-catch gorgonians were recovered and returned to the continental shelf (at 80–90 m depth). The monitoring surveys performed by using an Autonomous Underwater Vehicle (AUV) revealed that 460 gorgonian transplants survived over an area of 0.23 ha. The reintroduced cold-water gorgonian population was compared to a reference natural population in terms of size and spatial structure. The cost of the restoration amounted to 140,000 €/ha, which is significantly lower than that of any deep-sea restoration actions performed to date. The results of this cost-effective active restoration highlight the viability of large-scale restoration of impacted cold-water coral communities, with promising results for the conservation and recovery of mesophotic and deep-sea ecosystems.
... Indeed, in Joubin (1922) the author already described the "problem" that CWCs supposed for bottom trawlers, as some of them had brought back on deck up to 6 tons of coral in a single trawl haul. Far from being a problem for this type of fishing gear, the detrimental effects of bottom trawling on coral gardens and reefs have been compared to those of forest clear-cutting (Watling and Norse, 1998). According to Fosså et al. (2002), almost 20 years ago, trawling activities in Norwegian deep-waters had already damaged ~30% of their CWC reefs. ...
Thesis
Scleractinian cold-water coral reefs are considered to be key hotspots of benthic biodiversity in the deep ocean. Due to their relevant ecological role and susceptibility to anthropogenic disturbances protection and conservation measures have been applied to these habitats, even though they are far from being completely understood. Throughout the last two decades several studies have quantitatively described the biodiversity of Atlantic cold-water coral reefs, finding considerable differences among biogeographic regions. In contrast, and probably owed to the scarcity of these habitats in the Mediterranean Sea, the knowledge related to coral reef biodiversity in this basin remains modest and almost purely qualitative. On a different note, when coral reefs are under persistent suitable environmental conditions and have a sufficient sediment input, they can develop and form large geomorphic structures known as coral mounds. The latter are sensitive to changes in climate and capable of recording such variations in the chemical composition of the coral skeletons. Numerous surveys in the Atlantic have associated coral mound development patterns to environmental variations caused by glacial-interglacial cycles. Within the Mediterranean, coral mound formation studies have been so far limited to the Alboran Sea and to the last 15 kyr, due to the lack of gravity cores encompassing longer periods of time. In this thesis a wide range of techniques, including ROV video-analysis, multivariate statistics, U-series dating, computed tomography and geochemical analyses were applied to acquire a better understanding of the spatiotemporal distribution of Mediterranean cold-water coral reefs and the processes controlling their evolution into mounds during the last 400 kyr. More precisely, the present study aimed to (1) quantify the density of uncommonly thriving coral reefs and accompanying megabenthic species within the Cabliers Coral Mound Province, and describe their distribution along it; and (2) explore which are the main environmental variables and paleoclimatic events that have controlled coral mound formation in Cabliers and in the newly discovered Tunisian Coral Mound Province. The research presented here revealed the densest and most flourishing cold-water coral reefs witnessed so far in the Mediterranean Sea and brought further insight into their distribution along the crests of ridge-like coral mounds. This thesis also contributed to increase our knowledge on the main species associated to Mediterranean coral reefs and their relative abundances, which showed considerable differences to those found in Atlantic reefs. In regards to coral mound formation, this work has expanded the current knowledge outside the Alboran Sea and back to 400 ka BP. Almost opposite development patterns were observed between the Cabliers and Tunisian coral mound provinces, with the former mainly developing throughout deglaciations and temperate interstadial periods and the latter during glacial periods. Nonetheless, both provinces seem to depend on a high surface productivity and an appropriate depth of the interface between Atlantic and Levantine Intermediate Waters for the coral mounds to develop. Lastly, the oceanographic alterations caused in the Eastern Mediterranean Basin during Sapropel events also seem to have had detrimental effects for coral mound formation in the Western basin.
... Bottom trawling represents the fishing practice with the highest impact on VMEs (Rogers, 1999;Maynou and Cartes, 2012;Probert, McKnight and Grove, 1997;Eigaard, Bastardie and Hintzen, 2017;Murillo et al., 2011;Puig et al., 2012). Its role in the degradation of VMEs is both direct, by scraping the seabed, resuspending the sediments and destroying habitat-formers, and indirect, by inducing long-term changes in the benthic community, reducing habitat complexity and affecting ecosystem functioning ( Jones, 1992;Roberts, 2002;Hinz, 2017;Jennings and Kaiser, 1998;Watling and Norse, 1998;Maynou and Cartes, 2012;Colloca et al., 2004;Gray et al., 2006). Although bycatch data from commercial fisheries are lacking, scientific trawl surveys can provide an insight into understanding the bycatch of VME indicator taxa (e.g. ...
... The COVID-19 outbreak has led to a historic crisis that forced governments across the planet to stop many economic activitiesespecially those deemed 'non-essential' -in order to stop the virus from spreading. Although the pandemic was seen as "an opportunity to revive the ocean and start building a sustainable ocean economy" [21] and to "reshape our economy to make it more resilient and sustainable [by] putting together the biggest package worldwide that links investments for recovery to the sustainable development spirit" [13], our study demonstrates that the subsidies under scrutiny -COVID aids for temporary cessationshave chiefly benefited large companies operating larger scale, higher impact fishing gears [51][52][53], while practices that are hailed for their lower impact (e.g. [53][54][55][56]) were marginalized, utterly ignoring the overarching principles of the CFP [11] and the ambitions targets set by the SDGs [14]. ...
Article
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The European Commission launched the Coronavirus Response Investment Initiatives in March 2020, which aimed to help European economic actors, including the fishing sector, to cope with the COVID-19 crisis. This initiative was translated into French law in April 2020, through a decree laying down conditions for obtaining temporary cessation subsidies. Here, we demonstrate that, in stark contradiction with the European Union's international commitments and binding objectives, France allocated this fund in a way that mostly benefited large-scale, high-impact fisheries. In particular, we show that seven companies/groups received 28.5% of all subsidies, for only 53 vessels, i.e. 0.8% of the French fleet. We also show that vessels smaller than 12 m and operating lower impact, 'passive' gears only accounted for 8.7% of subsidies although they account for 74.5% of the French fleet. In contrast, vessels larger than 12 m (and up to 89.4 m) and operating higher impact, 'active' gears captured 70.5% of all subsidies, although they only account for 10.7% of the fleet. These results support the fact that despite celebrated commitments and objectives aiming to support low impact, coastal communities and to rebuild thriving marine ecosystems — including during the COVID-19 crisis — a key fishing state such as France keeps implementing policies that are tailored by and for the most powerful companies and impactful fishing practices.
... Bottom trawling impacts marine habitats in three main aspects: i) physical, due to direct changes in the seabed structure [1], causing the resuspension of sediment (sediment's matrix disruption) and injury or death of many benthic organisms [2][3][4]; ii) chemical, affecting the organic carbon mineralization [5,6] and re-inserting into the water column possible a1111111111 a1111111111 a1111111111 a1111111111 a1111111111 contaminants such as mercury [7]; and iii) biological, mainly given its high level of non-targeted catch [8][9][10], mostly composed of small sized individuals, usually juveniles [11,12]. ...
Article
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We used complementary stable isotope (SIA) and stomach content (SCA) analyses to investigate feeding relationships among species of the nektobenthic communities and the potential ecological effects of the bottom trawling of a coastal ecosystem in northeastern Brazil. Carbon (δ13C) and nitrogen (δ15N) compositions were determined for five basal sources and 28 consumers, from zooplankton to shrimp and fish species. Fishes and basal sources showed a broad range of δ15N (fishes: 6.49–14.94‰; sources: 2.58–6.79‰) and δ13C values (fishes: -23.86 to -13.71‰; sources: -24.32 to -13.53‰), while shrimps and crabs exhibited similar nitrogen and carbon ratios. Six trophic consumer groups were deter- mined among zooplankton, crustaceans and fishes by SIA, with trophic pathways associ- ated mostly with benthic sources. SCA results indicated a preference for benthic invertebrates, mainly worms, crabs and shrimps, as prey for the fish fauna, highlighting their importance in the food web. In overall, differences between SCA and the SIA approaches were observed, except for groups composed mainly for shrimps and some species of high δ15N values, mostly piscivorous and zoobenthivores. Given the absence of regulation for bottom trawling activities in the area, the cumulative effects of trawling on population param- eters, species composition, potentially decreasing the abundance of benthic preys (e.g., shrimps, worms and crabs) may lead to changes in the trophic structure potentially affect the food web and the sustainability of the fishery.
... Bottom trawling represents the fishing practice with the highest impact on VMEs (Rogers, 1999;Maynou and Cartes, 2012;Probert, McKnight and Grove, 1997;Eigaard, Bastardie and Hintzen, 2017;Murillo et al., 2011;Puig et al., 2012). Its role in the degradation of VMEs is both direct, by scraping the seabed, resuspending the sediments and destroying habitat-formers, and indirect, by inducing long-term changes in the benthic community, reducing habitat complexity and affecting ecosystem functioning ( Jones, 1992;Roberts, 2002;Hinz, 2017;Jennings and Kaiser, 1998;Watling and Norse, 1998;Maynou and Cartes, 2012;Colloca et al., 2004;Gray et al., 2006). Although bycatch data from commercial fisheries are lacking, scientific trawl surveys can provide an insight into understanding the bycatch of VME indicator taxa (e.g. ...
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This publication offers an overview of historical and current trends in the bycatch of five important groups of vulnerable species in the Mediterranean and the Black Sea: seabirds, sea turtles, elasmobranchs, marine mammals and macrobenthic invertebrates. Interactions between these groups and fisheries are known to occur in the context of nearly all commonly used types of fishing gear and can result in injury or death to the animals. Each chapter in this review focuses on one of the five groups of vulnerable species, describing and presenting data from surveys and studies conducted over recent decades. The chapters are further subdivided according to fishing gear and GFCM subregion (western, central and eastern Mediterranean, the Adriatic Sea and the Black Sea). The incidental catch records included in this review are derived from a variety of approaches. Surveys completed by onboard observers, while demanding more time and resources, represent the most comprehensive and accurate of these methods. Less reliable data come from non-systematic, opportunistic data collection, such as questionnaire surveys answered by fishers. Though many geographic areas and vessel groups remain underrepresented in the available data, coverage has generally increased in recent years and insight continues to emerge on the key dynamics governing the bycatch of vulnerable species in the Mediterranean and Black Sea. Seabird bycatch has mainly been recorded from the western Mediterranean and in longline fisheries. Bottom trawlers, on the other hand, have the greatest impact on sea turtles, especially in the northern Adriatic Sea, Tunisia, Egypt and Turkey. The vessel groups most implicated in elasmobranch bycatch vary by subregion, with longliners accounting for nearly 80 percent of incidental captures in the central Mediterranean, for example, while pelagic trawlers are responsible for an even greater majority of incidental captures in the neighbouring Adriatic Sea. Historically, marine mammals were often caught in large-mesh driftnets, but the incidental capture of these species has declined since bans on driftnets were put in place in the late 1990s. Unsurprisingly, macrobenthic invertebrates, including soft and hard corals, sponges, echinoderms and molluscs, are most affected by bottom trawls, as they are dragged across the seafloor these species inhabit. Vulnerable species are not the only ones to come out the worse for wear from their interactions with fishing activities. Fishers also risk economic losses resulting from damage done to their nets by entrapped individuals or from the depredatory behaviour of species that feed on bait meant to lure target species. Raising awareness amongst fishers and relevant stakeholders of the threats currently facing vulnerable populations across the Mediterranean and the Black Sea, as well as their importance to local ecosystems, will help to improve relations between fisheries and these species and to ease transitions toward safer practices. New technologies that can mitigate the bycatch of vulnerable species must continue to be tested and implemented in fisheries and standardized procedures for data collection should be established to better understand the many factors influencing bycatch in the region.
... Following the PFMC's assessment of essential fish habitat (EFH) in 2006, NOAA fisheries established 51 groundfish EFH conservation areas (EFHCA) which were restricted from bottom trawling through Amendment 19 of the FMP [41,44]. Research continues to advance regarding the effects of fishing gear on the economic value of fisheries long-term [45]. ...
Article
Globally, coastal nearshore regions are an intersecting point for human and biological productivity, often serving as hotspots for subsistence, commercial, and recreational fishing activities. Despite this, many nearshore areas remain poorly understood, monitored or managed. This case study examined the nearshore sector of Oregon’s groundfish trawl fishery, which exists in shallow estuarine and continental shelf habitats common along the West Coast of North America; areas that are important for early life history stages of many commercial and recreational fisheries. The West Coast groundfish fishery includes over 90 different species, 40 of which occur within Oregon’s nearshore (here defined as the portion of the shelf extending seaward to a water depth of 200 m). The very shallow portions of the Oregon Coast (the area of the shelf inshore of 55 m) have been subject to limited scientific survey monitoring, and much of the details of the ecology, health, and processes in these habitats remain poorly understood. The utilization of the nearshore region by the commercial groundfish trawl fleet is also minimally documented despite the fact that experiential knowledge (local ecological knowledge [LEK]; trawl logbooks, fish tickets, interviews) exists. This research explored the capacity of capturing LEK sources to inform and enhance understanding of the drivers of effort and the vitality of nearshore fishery resources. Our approach used statistical analysis and mapping of nearshore trawl effort from 1981 to 2017 and gathered semi-structured interviews of intergenerational fishermen to bolster data-poor areas. Insights provided by sampling strategies and historical to current knowledge of access to groundfish assemblages provide informed baselines for future management. Spatial mapping results revealed a decline in trawl effort on the Oregon continental shelf thought time. Logbook and interview data assessment illuminated market and ecological drivers of fishing behavior as well as a unique sector of the groundfish fleet in Oregon: the beach fleet, with unique market and socio-economic challenges. Findings indicate a mixed-methods approach can provide a more thorough assessment of long-term interest in Oregon’s nearshore groundfish fishery. Ensuring better understanding of coastal interfacing regions such as Oregon’s nearshore insights potential for better conservation and utilization of marine resources and improved monitoring in resource limited management contexts.
... The RMTI, using a reformulation of the FiB index uses the trophic levels and catches of all taxa in an ecosystem, along with the efficiency of transfer between trophic levels to decompose trends in the mean trophic level of catches into inshore, mid-shore and offshore. Here, the RMTI shows that the fisheries of the Arabian Sea LME, like most fisheries in the world, increasingly rely on catches lower in the food web (generally smaller organisms), i.e. that they are 'fishing down the food web' (Pauly et al. 1998) and tightly controlling industrial fishing, both domestic and foreign, with particular emphasis on reducing or banning bottom trawl fisheries which are known to be highly wasteful (Cashion et al. 2017) and damaging to ecosystem structures that underlie most stock production (Watling and Norse 1998), and (2) assisting and empowering well-managed small-scale fisheries for both national consumption (food-and nutritional security, Golden et al. 2016) and carefully controlled and monitored export fisheries. This is the direction in which all fisheries around the world need to be heading (Zeller and Pauly 2019), to ensure the survival of a blue economy (Pauly 2018). ...
Chapter
The fisheries of the Arabian Sea Large Marine Ecosystem, which includes the northern part of the western Indian Ocean, from the Horn of Africa to India’s Malabar Coast are described, along with some of the physical parameters impacting on their productivity. The bulk of fishing and thus the majority of catches in the Arabian Sea occur within the exclusive economic zones of the bordering countries, which allow national governments to control and manage the exploitation of marine resources, allowing for potentially better control compared to most fishing in the high seas waters. Some progressive and forward-looking actions seem to have been taken on some issues plaguing fisheries, but most countries around this LME struggle with massive overcapacity, often enhanced by poor policy choices made in the past, especially with regards to the ill-advised preference given to industrial fisheries development at the expense of small-scale, food-security and livelihood fisheries. Serious considerations ought to be given by all these countries to reducing and tightly controlling industrial fishing, both domestic and foreign, with particular emphasis on reducing or banning wasteful bottom trawl fisheries and assisting and empowering well-managed small-scale fisheries.
... Low-relief habitats (relic oyster reefs, sand/ shell shoals) on the inner continental shelf serve as refuge for a wide variety of reef-dependent fishes during early life (Rooker et al. 2004, Wells et al. 2009), including several taxa of high ecological and economic value (e.g., snappers, groupers, triggerfishes). Unfortunately, low-relief habitat is frequently altered or lost due to anthropogenic disturbances (i.e., dredging, trawling; Fogarty and Murawski 1998, Watling and Norse 1998, Thrush and Dayton 2002, and as a result, the limited availability of this valuable nursery may represent a population bottleneck for reef fishes. Coastal land loss and beach erosion have increased the demand for shelf sand resources, with~28 million m 3 of sand mined per year from U.S. waters over the past decade for the purposes of beach renourishment (Elko et al. 2021). ...
Article
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Coastal restoration projects to mitigate environmental impacts have increased global demand for sand resources. Unfortunately, these resources are often extracted from sand/shell banks on the inner continental shelf, resulting in significant alteration or loss of low‐relief reefs in coastal oceans. Experimental reefs (oyster shell, limestone rubble, composite) were deployed in the western Gulf of Mexico to assess their potential value as nurseries for newly settled reef fishes. Occurrence, abundance, and species richness of juvenile fishes were significantly higher on all three types of low‐relief reefs compared with unconsolidated sediment. Moreover, reefs served as nursery habitat for a range of reef fish taxa (angelfishes, grunts, sea basses, snappers, and triggerfishes). Red snapper (Lutjanus campechanus) was the dominant species present on all experimental reefs (100% occurrence), and mean density of this species was markedly higher on each of the three low‐relief reefs (>40.0 individuals/reef) relative to comparable areas over unconsolidated sediment (0.2 individuals). Our results suggest creation or restoration of structurally complex habitat on the inner shelf has the potential to markedly increase early life survival and expedite the recovery of exploited reef fish populations, and therefore may represent a critical conservation tool for increasing recruitment and maintaining reef fish diversity.
... However, post-hoc analyses showed that the effect of 'Protection' was significant only in 3 out of 15 locations and only in one case did the no-take area have a higher AI score than outside. This is not surprising since human-driven disturbance in coastal areas may mostly affect benthic assemblages but not substrate topography (Watling and Norse, 1998;Guidetti and Boero, 2004;Rovere et al., 2009), with the exception of highly-destructive practices severely damaging the habitat (e.g. date mussel illegal harvesting, see Rovere et al. (2009) andColletti et al. (2020)). ...
Article
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Marine Protected Areas (MPAs) have been proved to effectively protect and restore fish assemblages. There is mixed evidence regarding the effects of MPAs on benthic assemblages, habitat complexity, and how protection might mediate the effects of habitat features (including biotic and abiotic components) on fish assemblages, with very little information concerning temperate areas. Here, our aim is to assess how protection 1) influences benthic assemblages and habitat complexity, and 2) mediates the effects of habitat complexity on fishes. Using non-destructive methods (photosampling for shallow rocky benthic assemblages, and underwater visual census using strip transects for fish assemblages) to characterize benthic and fish assemblages, we sampled 15 Mediterranean locations, each including protected and unprotected sites. In all, we sampled 90 sites, and analyzed 2,760 photos and 800 replicated transects, gathering information on 44 benthic and 72 fish taxa. Abiotic, biotic and synthetic (i.e. combining the previous two) complexity indices have been computed to synthesize habitat features. Overall, whole benthic assemblages did not significantly differ between protected and unprotected conditions, but higher cover of the ecologically important erect algae belonging to the genus Cystoseira sensu lato was recorded within MPAs. Abiotic, biotic and synthetic complexity did not show clear patterns related to protection levels, displaying inconsistent responses between different locations. Our findings highlight that protection has a generally positive effect on fish biomass, this latter variable responding independently of the habitat complexity. Our study, in conclusion, confirms that MPAs can be effective to protect and restore rocky-reef assemblages, highlighting the need for more in-depth exploration of the mechanisms determining the different responses of benthic taxa to protection and how this can influence the associated fish assemblages.
... Fishing activities generate major disruptions in ecosystems such as the decline of fish population abundance (Worm et al. 2009), changes in the physical structure of the environment (Kaiser et al. 2002), reduction of mega-fauna and predators, and non-targeted species by bycatch (Komoroske and Lewison 2015) and damage to benthic habitats (Kaiser et al. 2002(Kaiser et al. , 2003. Declines and extinctions can be associated with the loss of essential habitat and vegetation, overfishing and aquatic pollution (Watling and Norse 1998). Another important threat or factors affecting marine ecosystems' vulnerability is the anthropogenic activities in the oceans and along coasts (Halpern et al. 2015). ...
Article
Marine ecosystem is threatened by a suite of climatic, anthropogenic, agricultural and aquacultural, and fishing stressors. Agriculture and anthropogenic activities are the major drivers of biodiversity loss by extensive use of pesticides and fertilizers, and encounter depleted soils and erosion due to unsustainable farming practices. This study provides an assessment of the various potential threats of that vulnerability of marine biodiversity in the Gulf of Mannar. The data was collected with a questionnaire that was distributed personally to more than 100 resource users from four districts of Gulf of Mannar Biosphere Reserve Trust (GOMBRT) in binary format. The data was then explored using the multivariate logit regression method, followed by Hosmer-Lemeshow test. The evaluation showed that all the determinants of various threats significantly affect the vulnerability of marine ecosystem. Among the studied factors, change in sea temperature, increase in fishing efforts, advanced farming practices, occurrence of endangered species, and tourism were the greatest threats (high log odds ratio), identified as the most important determinants affecting marine ecosystem.
... In the last century, unsuitable management of fisheries, including artisanal, industrial and recreational, has led to overexploitation of marine resources in most of the world's coastal areas (Mitcheson et al. 2013;Chiappone et al. 2004;Pauly 2008;FAO 2012), while fishing methods such as trawling are contributing to a continuous degradation of marine habitats worldwide (Messieh et al. 1991;Collie et al. 1997;Watling and Norse 1998;Eno et al. 2013). In many areas of the globe, however, promotion of sustainable fisheries is complex, e.g. ...
Article
Unsuitable management of fisheries may lead to overexploitation of marine resources. Oceanic islands with narrow continental shelves, in particular, are sensitive to unsustainable levels of fishing intensity. Fish traps are the modality of artisanal professional fishing more important in the coastal waters of the Canary Islands (eastern Atlantic) to capture demersal resources, which are deployed all year-round and allow a release of undersized captures. We aimed at studying the structure of nearshore fish assemblages through deployment of benthic bottom traps carried out at Gran Canary Island. A quantitative description of catches, in terms of abundance, biomass and sizes, of traps deployed from May to October 2009, between ca. 20 to 50 m depth, was carried out. We used this information to test whether the structure of nearshore fish assemblages at the island scale varied between three zones located at the NW, NE and E of the island with varying habitat structure. A total of 58 species (22 families) were collected for the overall study from a total of 2568 deployed traps. The species Sparisoma cretense (25% of the total biomass), the family Sparidae (16 species, 44%) and Mullus surmuletus (4%) accounted for more than 73% of the total catch in terms of biomass. The parrotfish, S. cretense, was the fish with the largest catches in terms of number of individuals, followed by Dentex gibbosus, Diplodus vulgaris, Stephanolepis hispidus, Chromis limbata and Mullus surmuletus. Differences in the structure of the fish assemblage at the island scale were not predicted by differences in the type of bottom. Fishing yields were similar between the NW (0.16 ± 0.02 kg trap −1 day −1) and NE side of the island (0.19 ± 0.01 kg trap −1 day −1), being lower at the E zone (0.15 ± 0.01 kg trap −1 day −1). The most abundant species, the parrotfish S. cretense, had a mean size close to its first maturity sizes (SFM 50), while both D. gibbosus and D. vulgaris were below SFM 50. In general, the mean size of Sparids was well below SFM 50 , an indication of overexploitation, while M. surmuletus and S. hispidus reached a mean size beyond their first maturity sizes.
... This observation was quite similar to the highly exploited NC Adriatic (Coll et al. 2007) and Thracian Seas (Tsagarakis et al. 2010), but different from Pagasitikos Gulf which presented considerably lower values, something that could possibly be attributed to its semi-protected regime where towed gears have not been operating for over 50 years. It has been demonstrat-ed that fishing may lead exploited ecosystems to a less mature state, while prohibiting fishing with towed gears may drive change in bottom complexity, as well as benthos and fish species composition from disturbed to mature ecosystems (Watling & Norse 1998). The ecosystem of Cyprus also seems to be in a more mature state and currently recovering from previous overexploitation, as suggested by a moderate impact of fishing that can probably be related to fisheries management measures taken regarding the reduction of the coastal fleet (Michailidis et al. 2019b). ...
Thesis
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The world’s fisheries are in crisis. The oceans are depleted and, as a result, fisheries catches are declining. Ocean warming and other human-induced stressors are also impacting the marine environment. Shifting marine ecosystems call for adaptable and responsive management strategies to minimize potential negative impacts on habitats and biodiversity, the economy and food security. This task can be particularly challenging in transboundary regions, such as the Mediterranean Sea, where fish stocks are shared between different countries and bilateral, collaborative and scientifically-informed actions need to be taken. The ecosystem based fisheries management requires that decision making should be based not only on the characteristics of particular commercial stocks, but on all components of the ecosystem. Consequently, a shift from single-species assessments to more complex ecosystem models that include multi-species trophic interactions, environmental and anthropogenic driving factors is needed. The Ecopath with Ecosim modelling suite has been widely used in the context of the ecosystem based fisheries management to describe exploited marine food webs and perform temporal and spatial simulations to analyze the impact of fishing activities and environmental drivers on aquatic ecosystems. Lack of data may impede the progress towards such more holistic modelling and management approaches. The gap between the current and the desired knowledge regarding the biology of Mediterranean and Greek marine fishes is large, with no information on key biological characteristics of more than 40% and 70% of the species, respectively. Such big data gaps increase the uncertainty in stock assessments and ecosystem models, thus hindering fisheries management. The results of stock assessment methods that have been developed especially for data-poor areas agree with numerous other studies and indicate that the vast majority of the Mediterranean and Greek stocks are in a bad state, with low biomass levels, as a result of the ongoing overexploitation. However, as demonstrated with the case study of Thermaikos Gulf, northwestern Aegean Sea, eastern Mediterranean, marine fish and invertebrate populations are in a better state, with high biomass levels and healthier size structure, within the boundaries of marine protected areas where permanent fishing restrictions apply. Protected areas serve as refuges for marine organisms and provide them with a safe place where they can live, grow, and reproduce as undisturbed as possible. Ecopath ecosystem models of two exploited semi-enclosed areas in Greece, Thermaikos and Pagasitikos Gulf, central Aegean Sea, revealed the immaturity of both systems probably due to the intense fishing pressure exerted on stocks by local fishing fleets that mostly consist of numerous small scale coastal vessels. However, Pagasitikos Gulf seemed to be in a better state, something that could be attributed to its long-term protection from destructive fishing practices with towed gears. Temporal simulations in both systems indicated an overall ecosystem degradation over time with declining biomass and catch trends, as a result of the combined impacts of fishing and environmental factors. In any case, different examined scenarios clearly showed that a reduction in total fishing effort by 10-50% would lead to proportionally higher biomass in the ecosystem. The associated short-term trade-off to the rebuilding of marine resources seemed to be the resulted lower catches that stem from less fishing. Spatial simulations and scenarios in Thermaikos Gulf supported the empirical data and demonstrated that marine protected areas were effective tools for rebuilding the biomass of exploited stocks within their boundaries, and also that their size and location played a significant role in the way that different organisms respond to protection. Nevertheless, it was indicated that in order to achieve the highest benefits of protection, marine protected areas would need to be accompanied by a parallel reduction in total fishing effort, rather than a redistribution of fishing activities that would just move the pressure on the boundaries of protected areas, causing a local increase of catches owing to the beneficial results of protection. To conclude, a complete fisheries management view requires a combination of both conventional single-species approaches and a more holistic consideration of the ecosystem that takes into account the effects of multi-species interactions, environmental parameters and fishing practices. The poor status of stocks in the Aegean Sea in general, but also in the disturbed ecosystems of Thermaikos and Pagasitikos Gulfs, as demonstrated by single-species stock assessment methods and ecosystem models, highlights the urgent need to collectively reconsider the exploitation of marine resources which might seem inexhaustible, but they definitely are not. Climate change and environmental forcing, that may have synergistic effects on ecosystems, are largely uncontrollable and unpredictable. Therefore, the answer to the question of sustainable exploitation of marine fisheries resources is the regulation of fishing activities, with spatial and temporal restrictions that will maintain fishing pressure at lower levels than the historical ones. Finally, there is a need to enhance the performance and reliability of models, which are valuable tools in fisheries and ecosystem management. This can be achieved through an effort to fill in the missing biological and fisheries knowledge gaps in the Mediterranean and Greek Seas and to address the current limitations and inherent uncertainty that characterizes models reducing their performance and predictive capacity.
... In this study, we find the spatial correlation between marine productivity and fishing effort highly depends on gear types, probably related to the distribution Based on SAU catch data, bottom trawling plays a dominant role in African waters, producing more than three times of fisheries catch than that of pelagic trawling in 2012-2016. As bottom trawling targets species that rely on the benthic food web, their fishing practice follows the spatial distribution of benthic fish and invertebrates and is often constrained within the continental shelf (Watling & Norse, 1998). Consistent with our findings, prior studies found that the most important factors for explaining the distribution of benthic fishes and invertebrates are photosynthetically active radiation, temperature, bottom depth, salinity, oxygen and substrate of the seafloor (e.g. ...
Article
Marine fisheries in African waters contribute substantially to food security and local economies in African coastal nations. Recently, there are growing concerns about the sustainability of living marine resources in these countries’ exclusive economic zones (EEZs) due to increased risks from climate change, pollution and potential over‐exploitation of fisheries resources by non‐African (foreign) countries. To effectively manage fishing activities and sustain marine resources in African waters, we need useful tools for characterizing the fishing activities in African waters. Here, we assess the utility of the Automatic Identification System (AIS) derived data for describing the spatial characteristics of African and foreign industrial fishing activities within the EEZs of African coastal nations. The results show that the AIS‐derived spatial pattern of industrial fishing activities in African waters is consistent with that of industrial catches derived from the Sea Around Us database. Across African EEZs, the spatial correlations between primary productivity and fishing effort highly vary by gear types, which emphasizes the importance of investigating specific fishing strategies when studying the effects of bottom‐up drivers on fishing effort. We find an EEZ‐specific spatial pattern for fishing efforts across African waters and identify some socioeconomic, political and geographic factors that likely affect the decision of fleets to fish in specific African EEZs. We conclude that AIS‐derived fishing data can be a useful complementary tool for characterizing the spatial pattern of industrial fishing efforts in African waters.
... These mounds provide structural habitat for many benthic and bottom-associated species (Stone, 2006;Husebø et al., 2002;Krieger and Wing, 2002;Auster and Langton, 1999). Unfortunately, human activities can quickly remove the ecosystem functions that took these corals hundreds to thousands of years to provide (Grigg, 2002;NRC, 2002;Watling and Norse, 1998). NOTE: Addamo et al. (2016) reclassified this coral as Desmophyllum pertusum. ...
Article
The Pourtalès Terrace is an exposed hard-bottom platform located south of the Florida Keys in 200–450 m depth with a diverse deep-sea coral ecosystem dominated by stylasterid hydrocorals, octocorals, and sponges that supports recreational and commercial fisheries. Portions of the Terrace have been designated as managed areas in the absence of detailed habitat maps, which hampers identifying ecological benefits derived from such management actions. Here we report analyses of historic Terrace physiographic and geologic data with more recent high-resolution bathymetric and benthic data to statistically derive a benthic community characterization across the Terrace. Multivariate analyses of faunal density from 42 standardized sites showed spatially distinct communities: East Terrace, West Terrace, Upper Terrace Edge, Sinkholes and Lophelia Coral Mound (the southernmost record of this habitat in the continental U.S.). These corresponded to physiographic divisions into an Upper Terrace comprised of Central and Karst-like regions, and Lower Terrace. A detailed description of these communities is provided. This study presents new insights into the Terrace benthic community spatial arrangement and is a necessary step towards facilitating benthic mapping. Our recommendations highlight the information needed for benthic habitat map creation and collecting data to determine if current conservation boundaries match management goals.
... It has been observed that S. savaglia specimens may be particularly impacted by fishing activities (Fig. 1b-c), such as trawling or ghost-nets (Bavestrello et al., 1997;Roberts and Hirshfield, 2004;Bo et al., 2014). Moreover, especially in the past, specimens have been collected as souvenirs ( Fig. 1d) (Barrajón Domenech et al., 2008;Artüz et al., 1990;Watling and Norse, 1998;Previati et al., 2010), an exploitation that, today can still be locally active (Andrea Costantini, personal communication). These pieces of evidence call for an increase in our efforts to raise awareness on the urgency of targeted monitoring and protection measures, to provide a detailed and updated distribution map, and to include this species in the design of current and future conservation strategies. ...
Article
Savalia savaglia is an ecosystem engineer listed as Near-Threatened by the IUCN, even though effective management and proper monitoring efforts to assess its distribution is still lacking. The record of large, long-established colonies can indicate the occurrence of areas with limited human local pressure. These areas may be considered as proxies for the creation of baselines of reference useful to design restoration strategies. The aim of this work was to update the distribution of Savalia's Mediterranean populations to develop an Ecological Niche Model, highlighting potential areas for future monitoring programs. Occurrence data were collected and harmonized into a single dataset using the scientific literature and validated observations to feed a presence-only MaxEnt model, obtaining a basin-level potential distribution of the species. The results of our study can support decision-makers in marine spatial planning measures including the preservation of mesophotic environments and prioritizing areas for conservation.
... Disturbances, whether it be natural or anthropogenic, can negatively impact the benthic environment and subsequently, the benthic organisms inhabiting the seabed and the many associated biogeochemical processes. This is especially the case for activities such as sand mining and bottom trawl fishing, which directly remove the upper portion of the seabed, often the most active zone in the seafloor (Mayer 1993;Watling and Norse 1998;Herman et al. 1999;Watling et al. 2001;Jennings et al. 2001). Furthermore, this removal creates an open area requiring replenishment of the sediment from natural transport processes and also the recolonization in order for the benthic community to recover (van Dalfsen and Essink 2001). ...
... The importance of this faunal group is recognized by the ISA and demersal fishes and scavengers are a baseline taxonomic group recommended for study. Changes in the abundance, composition, and size distribution of deep-sea fishes and shrimps have been documented in response to direct activities such as fishing and to its indirect habitat alteration (Watling and Norse, 1998;Devine et al., 2006;Morato et al., 2006;Puig et al., 2012;Pusceddu et al., 2014;Mindel et al., 2017) and in at least one case for mine tailings disposal at upper bathyal depths (Brewer et al., 2007). Fishes and mobile scavengers have been sampled in the CCZ during various programs (Jones et al., 2017;Linley et al., 2017;Harbour et al., 2020) and ecologically, they are an important group for a regional synthesis. ...
Article
Full-text available
We synthesize and analyze data from visual transecting approaches and baited camera studies to evaluate fish and invertebrate scavenger communities across the Clarion-Clipperton Zone (CCZ), an area of intense deep-sea mining interest, and neighboring areas of the abyssal Pacific. In abyssal regions including the CCZ most of the top predators are large mobile fishes and crustaceans, and the majority of these are also opportunistic scavengers. Top predators can exert important ecosystem influences and they can be susceptible to sustained anthropogenic disturbances, necessitating their study in the CCZ mining region. In total 157 baited camera deployments from 3 mining exploration license areas, 4 APEIs (Areas of Particular Environmental Interest – one type of no mining zone) and 4 other areas in the Pacific (Hawaii, California, New Zealand and Guam) and 122 visual transects from 7 exploration license areas, 4 no mining zones, and the Peru Basin (DISCOL area) were examined. Many taxa were observed in both sampling techniques but visual transects viewed few fishes overall. Fish and scavenger communities and diversity varied across the CCZ, significantly for baited camera data with a parallel but insignificant pattern for visual transects suggesting that even for these highly mobile species, not all regions of the CCZ are equivalent and the CCZ cannot be managed as one homogenous region. Further CCZ communities were different than communities elsewhere in the abyssal Pacific. The regional variations in community composition are largely the result of varying abundances of species rather than species presence/absence given that most, but not all, of the fishes and scavengers observed have very large ranges. On a more local scale, seamounts had a significantly different scavenger community than neighboring abyssal plains and thus contribute to regional diversity. Visual transect data revealed a similar but insignificant pattern due to low sample sizes. Given the coarse spatial resolution of sampling of fish and scavenger communities in the CCZ, it is not possible to evaluate if no mining zones (APEIs) adequately represent these communities nor where, or if, any biogeographic boundaries exist in the CCZ region. It is possible to conclude that a network of APEIs that covers the spectrum of available habitats at regional and more local scales will be key to conserving fish and scavenger biodiversity.
... The summary statistics indicate that the Thermaikos Gulf is an immature system, with a high system production, much above zero, that exceeds respiration (Table 1), probably owing to its intense exploitation by numerous fishing vessels, including bottom trawlers. It has been shown that fishing exploitation may lead the ecosystem to a less mature state, whereas banning fishing with towed gears may drive change in bottom complexity, as well as benthos and fish species composition from disturbed to mature ecosystems (Watling and Norse, 1998). These results were quite similar to the highly exploited northern Adriatic (Coll et al., 2007) and Thracian Seas (Tsagarakis et al., 2010), but different from Pagasitikos Gulf that is under a semi-protected regime with towed gears being prohibited for half a century (Dimarchopoulou et al., 2019b). ...
Article
Ecosystem modelling constitutes a useful tool for the ecosystem approach to fisheries management, which demands a shift to more complex models that include multi-species trophic interactions, environmental and anthropogenic forcing. The Thermaikos Gulf is a shallow gulf in the northwestern Aegean Sea (Greece) and one of the major fishing grounds of the northeastern Mediterranean concentrating high fishing effort of trawlers and purse-seiners and producing more than 20% of the total Greek catches. In the present work, we developed an Ecopath base model and ran Ecosim simulations for 26 years (2000–2025), including the calibration period (2000–2016), aiming to describe the food web structure and function of the Thermaikos Gulf, identify main components and interactions among the 33 functional groups, assess the ecosystem impacts of fishing over time and compare ecosystem properties with other Mediterranean areas. Overall ecosystem degradation with biomass and catch decline was observed at the end of the calibration period due to the impact of environmental factors and fishing activities. The ecosystem seemed to stabilize in an intermediate state by the end of the projection years, but with an overall biomass and catch decline. Fishing effort reduction after 2016 resulted in higher biomass and catches compared to 2014–2015, that could not however reach the 2000 levels in most cases. The examined fishing effort reduction scenarios clearly showed that the more the fishing effort is reduced, the higher the biomass in the ecosystem and the lower the catches obtained compared to the baseline scenario. In a nutshell, since environmental drivers may be harder to predict or control, lowering the exploitation levels is an important step towards the rebuilding of overfished marine resources and more resilient ecosystems.
... Yet Scotland's recent Marine Assessment (Moffat et al. 2020) identified pressure from bottom-contacting gear (e.g., trawling and dredging) as one of the most widespread and direct pressures across all Scottish marine regions. These practices can alter the physical and biological characteristics of seabed habitats, posing an immediate threat to essential herring spawning grounds (Watling and Norse 1998;Ryan and Bailey 2012). While ~ 7% of Scottish inshore waters are included in a network of Marine Protected Areas (MPAs), bottom-towed gear is only prohibited in 2.5% of the inshore MPA network (Langton et al. 2020). ...
Article
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Scotland once had the largest herring fishery globally, generating local income, identity, and societal change. Following historic stock collapse, in spring 2018/2019 large herring shoals were observed on the west coast for the first time in decades, at a formerly important spawning ground. This highlights the urgency of maintaining historic (and contemporary) benthic spawning habitat, which these fish rely upon, in good condition. However, information on exact location, characteristics, and status of historic and contemporary spawning grounds, if existing, is not easily accessible. We searched over 1190 literature sources, dating back to 1884, using scientific databases and web-based searches, and ran a query for automated search of comprehensive historic reports. We present current knowledge on Scottish herring spawning grounds, retrieved through these searches and fisher interviews, maps showing historic and contemporary spawning grounds, and discuss challenges arising from the methods used to recognize these grounds. Knowledge gaps regarding location and environmental status of past and current spawning grounds, particularly relevant for Scotland’s west coast, are identified. Based on the importance of specific environmental and physical variables for herring reproductive success, we advocate the inclusion of essential spawning grounds into herring management plans. This will require additional data on spawning grounds, including historic local ecological knowledge rarely considered. An inclusive ecosystem-based approach to herring management would allow more targeted actions to conserve (and potentially restore) essential spawning habitat. More effective management strategies will also call for reversing the (global) issue of the disconnect between different stakeholder groups. Graphical abstract
... Likewise, we have lost more than half of global wetlands (54%-57%) over the past several centuries and the rate of loss has increased dramatically since 1900 (Davidson, 2014;Dixon et al., 2016). Damage to aquatic ecosystems is more complex to quantify but similarly expansive (Dudgeon et al., 2006;Halpern et al., 2015;Luypaert et al., 2020;Pandolfi et al., 2003;Reid et al., 2019;Watling & Norse, 1998). While some habitat destruction is also Percent of threatened species category is the main threat F I G U R E 2 Percent of threatened species in which a given major threat category is the primary factor driving the species toward extinction (International Union for Conservation of Nature, 2019a). ...
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The growing human population is responsible for a massive decline in species, biodiversity, and ecosystems across the globe. If we are to significantly slow these losses, the attention and resources devoted to individual causes should be commensurate with the magnitude of their contribution to the problem. The purpose of this study was to determine the relative magnitude of five major threats to species identified by the International Union for Conservation of Nature (IUCN) as threatened with extinction. Specifically, we analyzed the entire IUCN Red List database to determine the percentage of threatened species affected by overexploitation, climate change, pollution, habitat destruction, and invasive species, diseases, and genes. We also randomly sampled a portion of the database to estimate the percentage of species for which each threat was the dominant threat placing them at risk of extinction. Of the 20,784 species for which data were available, 88.3% were impacted by habitat destruction, 26.6% by overexploitation, 25% by invasives, 18.2% by pollution, and 16.8% by climate change and weather. Focusing on dominant threats, the percentage of species for which a given threat was the main factor pushing them toward extinction was as follows: habitat destruction 71.3%, overexploitation 7.4%, invasives 6.8%, pollution 4.7%, climate change, and weather 1.8%. Regardless of how percentages are calculated, habitat destruction threatens more species than all other categories combined, climate change the fewest. From the perspective of species and biodiversity conservation, these data suggest that a significant change in global environmental priorities is needed. Habitat destruction should become a greater focus of global environmental efforts and receive the attention and resources appropriate to the extraordinary magnitude of its impact. Moreover, while it is important to address all environmental problems, given the disproportionate impact habitat destruction has on species, care should be taken to avoid solutions to other problems that exacerbate this destruction. We analyzed the entire publicly available IUCN Red List database to quantify the percentage of species threatened with extinction that are impacted by each of five major threat categories: habitat destruction, climate change, overexploitation, pollution, and invasive species/diseases/genes. Our results show that more species are threatened by habitat destruction than all other threats combined, with climate change affecting the fewest species. These findings suggest a significant reordering of global environmental priorities is in order.
... In the present study the Highly trawled site was located along the continental slope on the Tromsøflaket where previous authors reported Porifera to make up the largest part of the megabenthic communities in weight and where the aggregations are the densest Gonzalez-Mirelis et al., 2021). The seascape impacts of trawling should not be ignored as a significant factor shaping community structure and function, since it has a similar effect as agricultural ploughing on land (Puig et al., 2012) and has been compared to forest clear cutting and replacement by intensive agricultural activities (Watling and Norse, 1998;Puig et al., 2012). ...
Article
In the Barents Sea, extensive aggregations of sponges are known to occur, especially in the southwestern portion dominated by large species of Geodia spp. The distribution of deep-sea sponge grounds, considered vulnerable marine ecosystems, often coincides with high fishing efforts targeting demersal fish species and benthic invertebrates using bottom trawls. The aim of this study was to investigate the effects of bottom trawling on the abundance of structure forming Geodia spp., size composition of Geodia barretti together with functional and species diversity of associated fauna. Using images collected by a Remotely Operated Vehicle, we compared two locations with contrasting levels of trawling effort. We found significantly smaller Geodia barretti in the intensely trawled area as well as differences in species and functional diversity between the two sites. This study provided clear evidence that bottom trawling significantly alter sponge associated communities, significantly reducing the abundance and size of geodiid sponges, and creating a shift in functional diversity. The effects of bottom trawling on Geodia barretti and Geodia spp. Grounds are noticeable and results should be used in conservation and management of these diverse sponge grounds.
... Bottom trawling generally requires heavy fishing gears and powerful engines with a high fuel consumption and CO2 emission (Turenhout et al., 2016). Bottom trawling homogenises sea floor texture, disturbs the sorting of sediment generated by natural or biological processes (Watling and Norse, 1998;Thrush et al., 2006;Hewitt et al., 2010), mobilises fine sediments into the water phase (Lucchetti and Sala, 2012;Puig et al., 2012), and may cause sediment systems to become unstable (Kaiser et al., 2002). Bottom trawls impact benthic communities by damaging habitats and by imposing direct mortality among animals that come into contact with the gear (reviews in Clark et al., 2016;Hiddink et al., 2017;Sciberras et al., 2018). ...
Technical Report
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This report presents the results of a four year research project “Impact Assessment Pulse trawl Fishery (IAPF)“ on the biological and ecological effects of electric pulse trawls used in the fishery for North Sea common sole (Solea solea).
... The dominant anthropogenic activities affecting marine ecosystems (Halpern et al., 2008) is without a doubt fishing. It is a global concern about adverse effects of various fishing gear, particularly bottom trawls, on seabed habitats and the structure and functioning of benthic ecosystems (Dayton et al., 1995;Jennings and Kaiser, 1998;Watling and Norse, 1998). These mobile, bottom-contacting gears have proven efficient for catching a range of fish and shellfish species and their use has increased globally since the 1950s (Valdemarsen, 2001;Watson et al., 2006). ...
Technical Report
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Two types of fishing gear, a traditional dredge on skis (Drag dredge/Drag gear) and a new design which uses set of wheels instead of skis (Berg´s sledge/ Berg‘s gear), were compared with regards to their impact on the bottom – as an estimation of environmental footprint. Results show that Berg´s sledge had smaller footprint on the bottom and less impact when colliding with obstacles. It is therefore concluded that even though Berg´s sledge is double the weight of the ski dredge it is more environmentally friendly.
... In 2016, there were reports (mostly anecdotal) of illegal catches directly targeting seahorses for TCM in the Ria Formosa lagoon, using beam-trawl devices (https://tinyurl.com/y9zko9oo). Bottom trawling has been reported to reduce the structural complexity of benthic communities, affecting epifauna and altering the sediment formation (Collie et al. 2000;Tuck et al. 1998;Watling and Norse 1998). Fishing with bottom trawling gears has the potential to cause population declines in some species vul nerable to exploitation, such as seahorses (Casey and Myers 1998;Kaiser et al. 1998). ...
Article
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After seahorse population fluctuations were revealed in previous studies, probably due to changes in their natural habitat, this study sought to determine the current status of the populations of the two existing seahorse species in the Ria Formosa lagoon, by revisiting previously surveyed sites, while assessing the main drivers for detected changes. Hippocampus guttulatus densities decreased significantly between 2002 and 2008, followed by a significant increase between 2008 and 2012 and a significant decrease between 2012 and 2018. There were no significant differences in H. guttulatus populations between the 2002 and 2012 surveys, and between 2008 and 2018. As for Hippocampus hippocampus, there were no significant differences comparing densities from all the different dates. Among the different variables tested in this study, holdfast coverage seems to have played a crucial role in seahorse decline. It is important to further assess the impact on seahorse populations of two recently reported events, the illegal fishing of seahorses and the expansion of Caulerpa prolifera algae in the Ria Formosa lagoon, South Portugal. Considering the existent threats and the probable causes behind the recent seahorse abundance decline, seahorses’ low densities make them even more susceptible to local extirpation due to continuous threats, which emphasizes the dire urgency to put in place mitigative actions to contribute to the conservation of these iconic species.
... Science has, for example, already extensively documented the damage that fishing with bottom trawls and dredges causes to marine ecosystems (e.g. Kaiser, 1998;Watling & Norse, 1998). Ocean life is fragile and should not be sacrificed to maximize short-term profits for a small number of companies and countries. ...
Article
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Of all the interconnected threats facing the planet, the top two are the climate and the biodiversity crises. Neither problem will be solved if we ignore the ocean. To turn the tide in favour of humanity and a habitable planet, we need to recognize and better value the fundamental role that the ocean plays in the earth system, and prioritize the urgent action needed to heal and protect the ocean at the ‘Earthscape’ level – the planetary scale at which processes to support life operate. The countries gathering at COP26 have unparalleled political capacity and leadership to make this happen. COP26 could be the turning point, but there must be commitment to united action for the ocean, as well as planning to meet those commitments, based on science‐led solutions that address the interconnectivity of the ocean, climate, and biodiversity. Key ways in which the ocean both contributes to and acts as the major buffer for climate change are summarized, focusing on temperature, but not forgetting the role of storing carbon. It is noted with ‘high confidence’ that the ocean has stored 91% of the excess heat from global warming, with land, melting ice, and the atmosphere only taking up approximately 5, 3, and 1%, respectively. We also highlight the impact of the recent large release of heat from the ocean to the atmosphere during the 2015–2016 El Niño. We then present six science‐based policy actions that form a recovery stimulus package for people, climate, nature, and the planet. Our proposals highlight what is needed to view, value, and treat the planet, including the ocean, for the benefit and future of all life.
... In addition, fishing has unintended consequences on biodiversity through bycatch of nontarget species and habitat damage. This includes bottom trawling, considered the most damaging form of fishing due to its indiscriminate, large-scale, and destructive nature, which is widespread on continental shelves and seamounts around the globe (Watling and Norse, 1998;Hiddink et al., 2017;Kroodsma et al., 2018). Trawling accounts for 26% of the global marine fisheries catch, and intrinsically results in extensive habitat damage and loss, extremely high levels of bycatch, and a large carbon footprint rivaling that of terrestrial food sources Steadman et al., 2021). ...
Article
In 2017, more than 15,000 scientists from 184 countries signed a second warning letter to humanity to caution against our continued wholesale destruction of global ecosystems (Ripple et al., 2017). Here, we reaffirm their message with a similar warning specifically focused on the ocean: humanity must immediately and significantly alter our harmful trajectory in order to avoid irrevocably damaging our oceans in multiple ways that will further affect ocean health for both us and future generations. The ocean is the world's largest realm, housing an astonishing array of biodiversity that provides critical ecological functions that ultimately support life on Earth. In this paper, we outline some of the significant ongoing and imminent activities that degrade ocean health, including destructive fishing practices, oil and natural gas extraction, seabed mining, coastal development, shipping, pollution, and greenhouse-gas emissions. We end by offering potential avenues to mitigate these impacts, including the cessation of particularly harmful activities, restoration of damaged habitats, strong protection of key and representative ecosystems, reduction in waste and emissions, and global policy shifts that prioritize ecosystem health.
... Overharvesting of wildlife can lead to disrupted interspecific interactions and ecosystem structure, altering species composition, functioning and services such as seed dispersal, pollination, and carbon storage (Costanza et al., 2017;Gardner et al., 2019). In wild marine fisheries, bottom trawling and dredging affect benthic species composition, most non-targeted, and modify the sea floor in ways similar to intensive land agriculture (Puig et al., 2012;Watling and Norse, 1998). ...
Article
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Illegal or unsustainable wildlife trade is growing at a global level, threatening the traded species and coexisting biota, and promoting the spread of invasive species. From the loss of ecosystem services to diseases transmitted from wildlife to humans, or connections with major organized crime networks and disruption of local to global economies, its ramifications are pervading our daily lives and perniciously affecting our well-being. Here we build on the manifesto ‘World Scientists’ Warning to Humanity, issued by the Alliance of World Scientists. As a group of researchers deeply concerned about the consequences of illegal or unsustainable wildlife trade, we review and highlight how these can negatively impact species, ecosystems, and society. We appeal for urgent action to close key knowledge gaps and regulate wildlife trade more stringently.
... Les activités de pêche par chalutage et dragage sont responsables de nombreux impacts sur les fonds marins, tels que la modification des communautés benthiques et des habitats sédimentaires (Newell et al., 1998 ;Ellis et al., 2000 ;Thrush et Dayton, 2002 ;Eigaard et al., 2017). Watling et Norse (1998) ont comparé les conséquences de la perturbation induite sur les fonds marins par les engins de pêche mobiles, à la coupe à blanc des forêts. Il a été démontré que le dragage des coquilles Saint-Jacques en mer d'Irlande modifie de manière significative les communautés benthiques et les populations de P. maximus dans des conditions de pression de pêche expérimentale et commerciale. ...
... Trawling and dredging fishing activities are responsible of many impacts on the sea bed, such as the modification of benthic communities and sedimentary habitats (Newell, Seiderer & Hitchcock, 1998;Ellis, Norkko & Thrush, 2000;Thrush & Dayton, 2002;Eigaard et al., 2017). Watling & Norse (1998) compared the consequences of disturbance induced on the sea bed by mobile fishing gear to forest clear cutting. Scallop dredging in the Irish Sea has been shown to significantly modify benthic communities and P. maximus populations under experimental and commercial fishing pressure conditions (Bradshaw et al., 2001). ...
Article
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1. Taxonomic and functional trajectories of benthic assemblages were studied in shallow soft-bottom sediments in the bay of Saint-Brieuc (Western English Channel). Changes were assessed at different spatial and temporal scales using a macrobenthic dataset based on 38 stations sampled in 1987 and 2019, coupled with data from one station sampled annually between 2005 and 2019 as part of the European Water Framework Directive monitoring programme. 2. Taxonomic trajectories indicated 1) changes in the structure and distribution of benthic assemblages, 2) an homogenization of the assemblages, and 3) significant functional shifts. 3. Fishing activities and nutrient enrichment are probably strong drivers of the observed changes, as suggested by the higher mortality rate of fragile, flexible, tubiculous and burrowing species, and the increase in the abundance of opportunistic species in the assemblages. Certain populations of macroinvertebrates seem jointly controlled by climate change and by the aforementioned local factors of disturbance. 4. The Community Trajectory Analysis framework appears as a new and interesting method to track ecological changes in marine ecosystems by measuring change with respect to a baseline state, to help define ecological recovery (station returning to the initial ecological state) and departure (station presenting increased changes over time), and to analyse trajectory similarity. 5. According to the degradation of habitat over time, we identify the need for the implementation of knowledge-based conservation strategies, especially within Natura 2000 sites.
... Despite their remote offshore location, the Salas y Gómez and Nazca ridges are not immune to the risks posed by human activities, including commercial fishing, pollution, climate change, and potential seabed mining (reviewed by Wagner et al., 2021). Bottom fisheries are frequently cited as one of the most damaging activities for deep-water coral and sponge habitats (Watling & Norse, 1998;Pusceddu et al., 2014), given the indiscriminate and destructive nature of the trawls, lines, and other equipment used. Suitable habitat for corals and sponges often overlaps with bottom fisheries due to the strong association of many demersal fish species with seamounts and similar features, as well as with the habitat structures created by corals and sponges themselves (Baillon et al., 2012;Kutti et al., 2014). ...
Article
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The Salas y Gómez and Nazca ridges are two adjacent seamount chains off the west coast of South America that collectively contain more than 110 seamounts. The ridges support an exceptionally rich diversity of benthic and pelagic communities, with the highest level of endemism found in any marine environment. Despite some historical fishing in the region, the seamounts are relatively pristine and represent an excellent conservation opportunity to protect a global biodiversity hotspot before it is degraded. One obstacle to effective spatial management of the ridges is the scarcity of direct observations in deeper waters throughout the region and an accompanying understanding of the distribution of key taxa. Species distribution models are increasingly used tools to quantify the distributions of species in data-poor environments. Here, we focused on modeling the distribution of demosponges, glass sponges, and stony corals, three foundation taxa that support large assemblages of associated fauna through the creation of complex habitat structures. Models were constructed at a 1 km ² resolution using presence and pseudoabsence data, dissolved oxygen, nitrate, phosphate, silicate, aragonite saturation state, and several measures of seafloor topography. Highly suitable habitat for each taxa was predicted to occur throughout the Salas y Gómez and Nazca ridges, with the most suitable habitat occurring in small patches on large terrain features such as seamounts, guyots, ridges, and escarpments. Determining the spatial distribution of these three taxa is a critical first step towards supporting the improved spatial management of the region. While the total area of highly suitable habitat was small, our results showed that nearly all of the seamounts in this region provide suitable habitats for deep-water corals and sponges and should therefore be protected from exploitation using the best available conservation measures.
... Trawling increased rapidly in the 1960s, and by the 1980s large fleets of trawlers were harvesting prey from the global oceans (Watson et al. 2006). More than two decades ago it was estimated that, annually, trawlers were sweeping an area of seabed equivalent to 50-70% of the world's continental shelves, and extensive areas were being exposed to repeated trawling (Watling and Norse 1998). Modern bottom trawlers alone (thus excluding midwater trawlers) were estimated to land about 19 million tons/year of fish and invertebrates between 2008 and 2010, almost one-quarter of global landings (Amoroso et al. 2018). ...
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Several populations of odontocete cetaceans, including at least 19 species, have modified their behavior and adapted to foraging in association with trawlers. We review information on odontocete interactions with different types of trawlers across 13 Food and Agriculture Organization fishing areas around the world. We also review knowledge gaps, the effects on odontocete ecology, distribution, behavior and social organization, the main mitigation options, and some management avenues that could help reduce incidental mortality. Trawlers involved in the interactions varied greatly in gear and target species, implying odontocetes have developed behavioral specializations to forage under a variety of conditions. Specialized behavior included venturing into a moving trawl net to feed on the organisms trapped in the net, feeding on fish stirred up by the net, extracting fish from the outer mesh, feeding on catch lost during hauling, and scavenging on discarded catch. Foraging behind trawlers facilitates access to prey, and in some instances may compensate for scarcity of natural prey within areas exposed to intensive fishing or environmental degradation. This opportunistic foraging strategy, however, exposes the animals to potential harm and mortality in trawl gear. The combined effect of facilitated foraging and bycatch on the status and trends of odontocete populations is unknown. The economic damage caused by odontocetes, e.g. in terms of loss of marketable catch and gear damage, remains largely conjectural. Attempts to reduce depredation and/or bycatch in trawl gear have included acoustic deterrents and exclusion devices installed in nets, although neither technique has proven to be consistently effective. --- https://doi.org/10.1007/s11160-022-09712-z
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Microbes in marine sediments constitute a large percentage of the global marine ecosystem and function to maintain a healthy food web. In continental shelf habitats such as the Gulf of Maine (GoM), relatively little is known of the microbial community abundance, biodiversity, and natural product potential. This report is the first to provide a time-series assessment (2017–2020) of the sediment microbial structure in areas open and closed to fishing within the Stellwagen Bank National Marine Sanctuary (SBNMS). A whole metagenome sequencing (WMS) approach was used to characterize the sediment microbial community.
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Augmenting habitat complexity by adding structure has been used to increase the population density of some territorial species in the wild and to reduce aggression among captive animals. However, it is unknown if all territorial species are affected similarly by habitat complexity, and whether these effects extend to non-territorial species. We conducted a meta-analysis to compare the behavior of a wide range of territorial and non-territorial taxa in complex and open habitats to determine the effects of habitat complexity on 1) territory size, 2) population density, 3) rate and time spent on aggression, 4) rate and time devoted to foraging, 5) rate and time spent being active, 6) shyness/boldness, 7) survival rate, and 8) exploratory behavior. Overall, all measures were significantly affected by habitat complexity, but the responses of territorial and non-territorial species differed. As predicted, territorial species were less aggressive, had smaller territories and higher densities in complex habitats, whereas non-territorial species were more aggressive and did not differ in population density. Territorial species were bolder but not more active in complex habitats, whereas non-territorial species were more active but not bolder. Although the survival of non-territorial species increased in complex habitats, no such increase was observed for territorial species. The increased safety from predators provided by complex habitats may have been balanced by the higher population densities and bolder behavior in territorial species. Our analysis suggests that territorial and non-territorial animals respond differently to habitat complexity, perhaps due to the strong reliance on visual cues by territorial animals.
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On the U.S. West Coast, reports of whales entangled in fishing gear increased dramatically in 2014. In this study, a time series of fishing activity maps was developed from 2009 to 2016 for the four fixed‐gear fisheries most commonly implicated in entanglements. Maps were generated using vessel monitoring system (VMS) data linked to port‐level landings databases, which were related to entangled whale reports over the same time period and with modelled distributions of humpback whales Megaptera novaeangliae Borowski. Over the full study period, neither marked increases in fishing activity nor changes in fisheries footprints within regions with high whale densities were detected. By contrast, a delayed fishery opening in California due to a harmful algal bloom in spring of 2016 led to ~5–7 times average levels of Dungeness crab Metacarcinus magister (Dana) fishing activity, which was consistent with a high rate of entanglement in that year. These results are consistent with current hypotheses that habitat compression caused by a marine heatwave increased the overlap of whales with fishing activity, despite minimal changes in the fisheries themselves. This study adds to literature on bycatch of protected species in otherwise sustainable fisheries, highlighting the value of using VMS data for reducing human–wildlife conflict in the ocean.
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The Salas y Gómez and Nazca ridges are underwater mountain chains that stretch across 2,900 km in the southeastern Pacific and are recognized for their high biodiversity value and unique ecological characteristics. Explorations of deep-water ecosystems have been limited in this region, and elsewhere globally. To characterize community composition of mesophotic and deep-sea demersal fauna at seamounts in the region, we conducted expeditions to Rapa Nui (RN) and Salas y Gómez (SyG) islands in 2011 and Desventuradas Islands in 2013. Remote autonomous baited-cameras were used to conduct stationary video surveys between 150–1,850 m at RN/SyG (N = 20) and 75–2,363 m at Desventuradas (N = 27). Individual organisms were identified to the lowest possible taxonomic level and relative abundance was quantified with the maximum number of individuals per frame. Deployments were attributed with associated environmental variables (temperature, salinity, dissolved oxygen, nitrate, silicate, phosphate, chlorophyll-a, seamount age, and bathymetric position index [BPI]). We identified 55 unique invertebrate taxa and 66 unique fish taxa. Faunal community structure was highly dissimilar between and within subregions both for invertebrate (p < 0.001) and fish taxa (p = 0.022). For fishes, dogfish sharks (Squalidae) accounted for the greatest dissimilarity between subregions (18.27%), with mean abundances of 2.26 ± 2.49 at Desventuradas, an order of magnitude greater than at RN/SyG (0.21 ± 0.54). Depth, seamount age, broad-scale BPI, and nitrate explained most of the variation in both invertebrate (R ² = 0.475) and fish (R ² = 0.419) assemblages. Slightly more than half the deployments at Desventuradas (N = 14) recorded vulnerable marine ecosystem taxa such as corals and sponges. Our study supports mounting evidence that the Salas y Gómez and Nazca ridges are areas of high biodiversity and high conservation value. While Chile and Peru have recently established or proposed marine protected areas in this region, the majority of these ridges lie outside of national jurisdictions and are under threat from overfishing, plastic pollution, climate change, and potential deep-sea mining. Given its intrinsic value, this region should be comprehensively protected using the best available conservation measures to ensure that the Salas y Gómez and Nazca ridges remain a globally unique biodiversity hotspot.
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A large (∼2450 km²) offshore (∼75 km) targeted fisheries closure (TFC) area was implemented on the North West Shelf of Australia (NWS) in 1998 as part of a suite of management controls to address overfishing concerns, and in the process to potentially mitigate any impacts of trawling to benthic habitats. Twelve years later, the benthic biota and fish assemblages in the TFC were assessed using stereo-video and compared with adjacent areas that have been consistently fished with a range of commercial fishing methods. The remote nature of the region has meant that these areas would be inaccessible to recreational fishers. After 12 years of protection there were significant differences between the TFC and comparable fished areas in both the composition and the height of biogenic structures, however the magnitude of these differences were subtle, except for branching soft corals, which were significantly taller in the TFC area. Despite the relatively young age of the TFC, significant differences in the fish abundance and biomass compositions were driven by the slower growing, longer lived and inherently less productive fishery target species. The abundance of Lutjanus sebae (red emperor) and Epinephelus multinotatus (Rankin cod), and the associated biomass of L. sebae and Pristipomoides multidens (goldband snapper) were all greater within the TFC. However, neither the abundance or biomass of the relatively shorter lived and more productive fishery species (e.g. the bluespotted emperor Lethrinus punctulatus and the brownstripe snapper Lutjanus vitta) were greater within the TFC. Growth rates of benthic biota across the NWS are unknown, however the limited detectable differences in benthic biota between the TFC and fished areas, suggests that either recovery of the the benthic biota is slow and may not yet be at a threshold for detection and/or alternatively that current fishing activities are not causing adverse impacts to biogenic structures. These large, offshore targeted fishery closures provide a useful reference point to examine the natural variability, growth and recovery of benthic biota and fish assemblages after the cessation of fishing.
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Model towing experiments of a bottom trawl net with hyper-lift trawl door were conducted to investigate the effect of the bottom sediment (concrete, sand, gravel, and rock) on the warp tension of the overall trawl system. The towing speed was from 50 cm/s to 70 cm/s and the ratio of warp length relative to the water depth was within the range of 4–6. Through the signal analysis of time-series warp tension, results reveal that there is a significant dependence of the warp tension on the type of bottom sediment, and the oscillation of warp tension in a frequency range of 1–10 Hz increases in the order of concrete, sand, gravel, and rock. Based on these characterizations, the time-series warp tension is thus represented by the feature vector for the input data of the self-organizing map (SOM) and learning vector quantization (LVQ) neural networks. A clustering method with an unsupervised SOM neural network acting as an updating tool for the bottom sediment database was successfully built using the validation of the prepared sediments. In combination with the output vector of labeled bottom sediment, the supervised LVQ neural network for sediment recognition performed excellently with a high classification accuracy of over 80%.
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In 2003, a large Lophelia pertusa reef complex was discovered on the southeast edge of the Scotian Shelf, representing the only known cold-water coral reef in Canada. Extensive damage to the reef from bottom fishing activities was apparent, which resulted in the establishment of the 15-km² Lophelia Coral Conservation Area (LCCA) in 2004 to prevent further damage and allow recovery. Since 2004, the effectiveness of the LCCA in achieving these objectives has never been assessed. Through the analysis of benthic images collected in 2003, 2009, and 2015, we evaluate the effectiveness of the LCCA in terms of its success in facilitating the recolonization and recovery of its target species, L. pertusa, and in conserving local benthic biodiversity. Using multivariate community analyses and generalized linear modelling techniques, we compare changes in the diversity, abundance, and composition of epibenthic megafauna within and outside its boundaries over the 12-year period. We observed an increase in epibenthic megafaunal species density and abundance over time that was higher inside the closure than outside, suggesting that the LCCA has facilitated the recruitment and recovery of the benthic communities within its confines. While recruitment of L. pertusa was low, the recent discovery of numerous undisturbed large mounds of live L. pertusa establishes a local recruitment source, a prerequisite for the reef structure to recover to its pre-disturbed state. We recommend that monitoring of the reef structure occur every 7-10 years to evaluate the settlement and growth of L. pertusa and the other deep-water corals that reside there.
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1. Beam-trawling is a source of physical disturbance to marine sedimentary communities in areas less than 50m deep, on the western European continental shelf. Chains attached between the beam-trawl shoes are designed to penetrate the upper few cm of the sediment, which leads to the damage or removal of some infaunal and epifaunal species. In some areas, beam-trawling may be frequent and intense, leading to speculation that it may generate long-term changes in the local benthic fauna. 2. As part of a larger MAFF study examining the ecological effects of beam-trawling, we investigated its local impact on an infaunal community in the north-eastern Irish Sea. Studies of this type are complicated by the heterogeneity of the environment, hence we adopted a replicated, paired control and treatment design to maximize the chances of detecting any effects due to trawling. 3. A side-scan sonar survey revealed that the experimental area was characterized by mobile megaripples in the south-eastern sector of the experimental area and stable sediments with uniform topography in the north-western sector. Multivariate analysis of the species abundances from the control areas separated the fauna into two distinct communities which corresponded to the different substratum characteristics. Data from the two regions were therefore treated separately when testing for the effects of trawling. 4. In the north-western sector, trawling led to 58% decrease in the mean abundance of some taxa and a 50% reduction in the mean number of species per sample. Multivariate analysis revealed that differences between control and fished sites were largely due to the reduction or removal of less common species. These effects were less apparent in the mobile sediments of the south-eastern sector, which had a naturally impoverished fauna and high level of heterogeneity. 5. Univariate variables, such as abundance and the total number of species per sample, indicated that the variation between replicate samples increased as a result of trawling disturbance. However, examination of the community data using an index of multivariate dispersion revealed no difference between fished and unfished areas. This suggests that the effects of fishing disturbance are consistent between replicate samples. 6. Fishing with demersal gears modifies communities in relatively stable sediments. Frequent and repeated physical disturbance by fishing gears may lead to long-term changes in the benthic community structure of these habitats.
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Fishers have been complaining about the effects of bottom trawl gear on the marine environment since at least the 14th century. Trawl gear affects the environment in both direct and indirect ways. Direct effects include scraping and ploughing of the substrate, sediment resuspension, destruction of benthos, and dumping of processing waste. Indirect effects include post‐fishing mortality and long‐term trawl‐induced changes to the benthos. There are few conclusive studies linking trawling to observed environmental changes since it is difficult to isolate the cause. However, permanent faunal changes brought about by trawling have been recorded. Research has established that the degree of environmental perturbation from bottom trawling activities is related to the weight of the gear on the seabed, the towing speed, the nature of the bottom sediments, and the strength of the tides and currents. The greater the frequency of gear impact on an area, the greater the likelihood of permanent change. In deeper water where the fauna is less adapted to changes in sediment regimes and disturbance from storm events, the effects of gear take longer to disappear. Studies indicate that in deep water (>1000 m), the recovery time is probably measured in decades.
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Seagrass meadows represent a distinct habitat in shallow coastal and estuarine ecosystems. We examine the role of seagrass meadows as an important habitat for fishes and large mobile invertebrates. In particular, we emphasize the importance of the structural complexity of the vegetation and associated algal components. Based on data from a variety of geographical localities we consider how vegetation density, plant morphology and associated sessile colonial animals can influence abundance and diversity of predator and prey species in vegetated areas on both local and regional geographical scales. In so doing we generate hypotheses that lead to predictions concerning: size of populations and the amplitude of their fluctuations in vegetated habitats at different latitudes; success rate of predators using different foraging strategies in vegetation of different densities; and resultant diversity and abundance of invertebrate prey, juvenile fish and adult fish in different densities of vegetation.
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1. The distribution of effort for the most frequently used mobile demersal gears in the Irish Sea was examined and their potential to disturb different benthic communities calculated. Fishing effort data, expressed as the number of days fished, was collated for all fleets operating in the Irish Sea in 1994. For each gear, the percentage of the seabed swept by those parts of the gear that penetrate the seabed was calculated.
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An important ecological issue is developing an understanding of how patterns and processes vary with scale. We designed a field experiment to test how differences in the aerial extent of disturbance affected macrofaunal recolonization on a sandflat. Three different plot sizes (0.203 m2, 0.81 m2, and 3.24 m2) were dafaunted, and samples were collected to assess recovery over a 9-mo period. As the sandflat used for the experiment was prone to disturbance by wind-driven waves, we also measured changes in sediment bed height (an indicator of sediment stability) over the course of the experiment. Most common species revealed significant relationships between density and disturbance plot size. Scale-dependent recovery was also demonstrated by differences in species assemblage structure over the course of the experiment. Relative rates of colonization varied by ≈50% between large and small experimental plots. However, these differences were not related to specific species, particular functional groups, or potential modes of colonizations. The results revealed an unusually slow rate of faunal recovery following defaunation. Both increasing numbers of colonists, and density changes in ambient sediments made an important contribution to recovery. The relationship found between changes in sediment bed height and wind velocity indicated that wind-driven wave disturbance was an important factor influencing sediment instability. Sediment instability was higher in all experimental plots than in the ambient sediments, due to the initial removal of a dense spionid polychaete tube mat characteristically found at the study site. Sediment instability also increased with increasing plot size. Thus in this dynamic sandflat habitat, faunal emigration from recovering disturbed patches of sediment may significantly slow rates of recolonization. These results demonstrate that incorporating patch size, emigration, recovery time, and interactions between hydrodynamic conditions and habitat stability (particularly where colonists influence sediment stability) are crucial to generating a general understanding of recovery processes in sof-sediment habitats. While our results demonstrate the need for caution in scaling-up from small-scale studies, they do indicate that larger scale disturbances that destroy organisms with a role in maintaining habitat stability are likely to result in very slow recovery dynamics, particularly in wave-disturbed soft-sediment habitats.
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