Modelling the Whole-Ecosystem Impacts of Trawling

Trawling has been controversial since its introduction in the 17th century. In 1882 the Fishery Board for Scotland was established and assigned powers to ban beam and otter trawling where necessary to protect traditional static gear fisheries. Under these powers, large parts of the inshore waters off the east and west coasts of Scotland were closed to trawling. The Firth of Clyde remained closed until 1962. More recently, in April 2015 solicitors acting for Greenpeace obtained High Court permission for a judicial review of Defra’s alleged failure to adjust its policy on allocating annual landing quotas to reflect reforms to the CFP. It is claimed the reforms stipulate that greater preference should be given to sustainable low impact fishing methods at the expense of high-impact methods such as trawling. In Scotland, the exclusion of trawling activity from a network of marine protected areas established in July 2015 has also been highly controversial. There is no doubt that some trawl gears can be extremely destructive of fragile habitats and slowly regenerating fauna such as coral. Over expanses of mud or sand, however, it has been claimed that trawling may be a positive factor, akin to ploughing the fields in terrestrial agriculture, and enhancing the productivity of the ecosystem. There have been many scientific studies, both in the field and using mathematical modelling, of the impact of trawling on the seabed. Similarly, we know very well that harvesting of fish and shellfish, whether using trawling or static gear, has consequences for marine food webs. However, there have been few, if any, scientific studies which have put these two aspects of trawling together and then compared the seabed impacts of trawling with the consequences of harvesting. In this project we used a mathematical model to compare and contrast the whole ecosystem effects of harvesting fish and shellfish with the consequences of other aspects of trawling activity, especially the ploughing of seabed habitats. The model is not detailed to the level of individual species or exact locations. Rather it gives results at the level of a whole regional sea area, such as the North Sea or the whole of the west of Scotland. The project had three main components. First, was the extension of an existing mathematical model of a marine ecosystem to include explicit representation of the ploughing effects that different gears have on seabed habitats. Second, an analysis of a large international data set on activity, landings and catches by different fishing gears in northwest European waters, and the mapping of these onto different seabed habitats to generate inputs to the model. Finally, we carried out a series of sensitivity experiments with the model. These experiments investigated the whole ecosystem effects of seabed ploughing by different gears, using food web indicators relevant to the EU Marine Strategy Framework Directive, and compared them with the impact of one scenario for implementing a landing obligation, and the potential impacts of a reduction in overall fishing activity. For the North Sea, the results show that even if all ploughing effects were eliminated, the effects on the whole ecosystem would be equivalent to only a 1% or less change in overall harvesting rate of fish and shellfish. This is a very small effect compared to the changes in effective harvesting rate implied by the improvements in gear selectivity required to achieve the landing obligation. For the west of Scotland region, the model showed that the food web was more sensitive to the effects of ploughing by fishing gears than in the North Sea, but the effect was still small compared to the consequences of activity reduction overall. The greater sensitivity of the west of Scotland to seabed ploughing arose because the disturbance rate of muddy sediments was around 5-times higher than in the North Sea, almost entirely due to the activities of TR2 Nephrops trawling. Despite our conclusion that the regional scale food web effects of seabed ploughing are small compared to the primary consequences of harvesting fish, this is not to say that there are no effects on regional biodiversity, or significant effects at local scales on specific habitats or vulnerable species. In particular the study identifies the TR2 gear fleet as being responsible for the majority of ecosystem-wide consequences of seabed ploughing. This gear has a particularly high ploughing rate and its activity is focussed on muddy sediments where the nutrient chemistry processes are more vulnerable to ploughing than in sandy and coarser sediments

Climate Change, ecosystem impacts and systemic risk

This report highlights some of the vital dependencies of human societies on ecosystems, the damages that can occur from them as a result of climate change, and the steps required to better understand and characterise the systemic risks to societies that result from such climate change-driven ecosystem damages

Literature Review of Gear-based Management Options in the Caribbean for Four Reef Fishing Methods: Fish Traps, Spears, Hook and Line, and Beach Seines

Many Caribbean reef fisheries have been overexploited for decades and often their decline has been accelerated by a loss of habitat. Improved management of Caribbean reef fisheries is vital to ensure their future sustainability. Reef fisheries in the Caribbean are difficult to manage due to the use of multiple fishing gear types, the number of species harvested, and the dispersed landing sites used by the fishers. Additionally, there is very little published information available on Caribbean reef fisheries and limited research into the effects of management. This review provides a synthesis of the published literature on four gears commonly used in Caribbean reef fisheries: fish traps, spears, hook and line, and beach seines, summarizing evidence on best management practices for each gear. The authors provide brief descriptions of each of the four gear types as well a synthesis of their use, biological impacts, and ecosystem impacts.The management recommendations are general recommendations on gear restrictions that could be applied to any Caribbean reef fishery

Strong fisheries management and governance positively impact ecosystem status

Fisheries have had major negative impacts on marine ecosystems, and effective fisheries management and governance are needed to achieve sustainable fisheries, biodiversity conservation goals and thus good ecosystem status. To date, the IndiSeas programme (Indicators for the Seas) has focussed on assessing the ecological impacts of fishing at the ecosystem scale using ecological indicators. Here, we explore fisheries Management Effectiveness' and Governance Quality' and relate this to ecosystem health and status. We developed a dedicated expert survey, focused at the ecosystem level, with a series of questions addressing aspects of management and governance, from an ecosystem-based perspective, using objective and evidence-based criteria. The survey was completed by ecosystem experts (managers and scientists) and results analysed using ranking and multivariate methods. Results were further examined for selected ecosystems, using expert knowledge, to explore the overall findings in greater depth. Higher scores for Management Effectiveness' and Governance Quality' were significantly and positively related to ecosystems with better ecological status. Key factors that point to success in delivering fisheries and conservation objectives were as follows: the use of reference points for management, frequent review of stock assessments, whether Illegal, Unreported and Unregulated (IUU) catches were being accounted for and addressed, and the inclusion of stakeholders. Additionally, we found that the implementation of a long-term management plan, including economic and social dimensions of fisheries in exploited ecosystems, was a key factor in successful, sustainable fisheries management. Our results support the thesis that good ecosystem-based management and governance, sustainable fisheries and healthy ecosystems go together.IOC-UNESCO; EuroMarine; European FP7 MEECE research project; European Network of Excellence Eur-Oceans; FRB EMIBIOS project [212085]info:eu-repo/semantics/publishedVersio

Marine Oil Snow Sedimentation and Flocculent Accumulation (MOSSFA) Workshop

The MOSSFA hypothesis is that the formation of marine snow/oil aggregates and its accumulation at the seafloor is related to events associated with the oil spill, various mitigation measures (e.g., the use of dispersants and in situ burning), and increased sediment-laden fresh water releases from Mississippi River impoundments. If this hypothesis is correct then this phenomenon takes on an added global significance as 85% of deep-water oil exploration occurs adjacent to deltaic systems. To better understand the sequence of events and the oceanographic processes involved, three of the Gulf of Mexico Research Initiative (GoMRI) funded Centers (C-IMAGE, DEEP-C and ECOGIG), all of which have Principal Investigators involved in the various aspects of the MOSSFA question, received funding to conduct two workshops related to Marine Oil Snow Sedimentation Flocculent Accumulation (MOSSFA). The intent of the first workshop was to bring together researchers working on MOSSFA to provide a synthesis of known facts, identify data gaps and propose follow-up research to help resolve key questions and uncertainties regarding the MOSSFA hypothesis

Metal contaminated dredged sediment derived soils: a case of diffuse contamination

Significant areas in Flanders, Belgium exhibit moderate contamination with trace metals caused by deposition or disposal of contaminated sediments. After disposal, the sediments develop into a soil- like material, on which vegetation is planted or develops spontaneously. Behaviour, cycling and ecosystem impacts of trace metals in calcareous dredged sediment disposal sites in Flanders was investigated. Although soil physico- chemical properties favour a low metal bioavailability, pore water concentrations can be elevated compared to pore water in uncontaminated soils. While metal leaching is not considered to be of concern, several plants accumulate elevated levels of Cd and Zn in leaves. Also metal levels in soil dwelling organisms and small mammals, particularly Cd, are elevated compared to reference situations. This raises concern for an enhanced transfer of metals to the food chain. A comprehensive knowledge of metal behaviour in these sites is essential for developing appropriate management options for these sites

Economic and Ecosystem Impacts of GM Maize in South Africa

White maize in South Africa is the only staple crop produced on a widespread commercial basis for direct human consumption using genetically modified (GM) cultivars. Using a combined economic and environmental approach, we estimate the total welfare benefits attributable to GM white maize in South Africa for 2001-2018 are $694.7 million. Food security benefits attributable to GM white maize in South Africa also manifest through an average of 4.6 million additional white maize rations annually. To achieve these additional annual rations using conventional hybrid maize, the additional land required would range from 1,088 hectares in 2001 to 217,788 hectares in 2014. Results indicate that GM maize reduces environmental damage by$0.34 per hectare or $291,721 annually, compared to conventional hybrid white maize

Performance in managing marine resources in the Bay of Bengal

The eight member countries were assessed as to their sustainable use of resources within their Exclusive Economic Zones(EEZs). Indicators included; investment in Marine Protected Areas (MPAs), impact of trawling, mariculture sustainability, protection of seabirds and marine mammals,ecosystem impacts, economic health and levels of reporting and compliance

Dispersal and remineralisation of biodeposits: Ecosystem impacts of mussel aquaculture

Suspension-feeding bivalves produce biodeposits (faeces and pseudofaeces) that have much higher sinking velocities than their constituent particles. Consequently they cause sedimentation of material that might otherwise not be deposited. The benthic remineralisation of biodeposits increases sediment oxygen demand and nutrient regeneration, thus enhancing the benthic-pelagic coupling of nearshore ecosystems. In New Zealand the mussel Perna canaliculus has a high natural abundance and is also intensively cultured. This thesis examines the dispersal and remineralisation characteristics of mussel P. canaliculus biodeposits and the impacts of sedimentation from a mussel farm in the Firth of Thames on sediment biogeochemistry by combining laboratory, field and modelling studies. Dispersal characteristics were examined in the laboratory by measuring sinking velocities and erosion thresholds of biodeposits produced by mussels of a wide size range fed three experimental diets. The results show that biodeposit dispersal is a function of mussel diet and size and thus could differ significantly between locations and seasons. Estimates of dispersal distances based on these results demonstrated that the initial dispersal of biodeposits produced by cultured mussels is not far. Depending on the hydrodynamic conditions, secondary dispersal via resuspension potentially plays a more important role in the dispersal of biodeposits from mussel farms than initial dispersal and almost certainly serves as the major means of transport of biodeposits from natural mussel beds. Biodeposit mineralisation was studied by incubating coastal sediments with added biodeposits and measuring oxygen and nutrient fluxes as well as sediment characteristics over an 11 d period. Sediment oxygen consumption and ammonium release increased immediately after biodeposit addition and remained elevated compared to control cores without additions for the incubation period. A biodeposit decay rate (0.16 d-1) was calculated by fitting a first-order G model to the observed increase in oxygen consumption. This rate is 1 - 2 orders of magnitude higher than published decay rates of coastal sediments without organic enrichment or plant material. Nutrient fluxes during the incubation period illustrated that biodeposit remineralisation alters the stoichiometry of the nutrients released from the sediments which may potentially be more significant than the changes of the individual fluxes. To determine the impact of a mussel farm in the Firth of Thames I measured sediment oxygen and nutrient fluxes by deploying benthic chambers, sediment characteristics by collecting sediment cores and sedimentation rates by deploying sediment traps in four seasons. Oxygen consumption and sediment nutrient release rates were generally higher under the farm compared to a reference site, demonstrating the typical response to increased organic input. Unusually low nitrogen release rates measured in summer may indicate enhanced denitrification under the farm. A simple budget demonstrated the importance of benthic nutrient regeneration in maintaining primary production in this region and that mussel culture can lead to a redistribution of nutrients. This study showed that site-specific hydrodynamic and biogeochemical conditions have to be taken into account when planning new mussel farms to prevent excessive modifications of nutrient dynamics. Results of the laboratory and field studies conducted in this thesis were used to parameterise, calibrate and validate models of mussel biodeposit dispersal and remineralisation. A particle tracking model showed that the maximum initial dispersal of faecal pellets from the mussel farm is approximately 300 m and that pellets can be transported several times this distance via resuspension. The remineralisation model was able to simulate the increased nitrogen fluxes from the sediments well and highlighted the need for thorough calibration and parameterisation of the model. This thesis contributed to the current understanding of the ecosystem impacts of mussel culture and provided numerical models and model parameters that will assist in the assessment of mussel culture sustainability and the contribution of mussels to the nutrient cycling in nearshore ecosystems