Bottom trawling and vulnerable marine ecosystems

Transcription

1 Bottom trawling and vulnerable marine ecosystems Seminar Current Issues In Marine Science Victoria University Wellington 12 March 2014

2 Outline of presentation What is the issue? What are vulnerable marine ecosystems? What has been done to protect VMEs to date? How well are mitigation measures working? What is being done to improve mitigation measures? What is the likely future fate of VMEs?

3 What is the issue? Bottom fishing causes significant disturbance to the seafloor and the integrity of habitats, communities and species is impacted trawled untrawled

4 What is the issue? Bottom fishing causes significant disturbance to the seafloor and the integrity of habitats, communities and species is impacted Many studies have demonstrated these effects in national waters, and concerns about the impact of bottom trawling outside areas national jurisdiction (i.e. the High Seas, 64% of the global ocean) came to a head in the late 1990s and early 2000s These concerns were articulated in 2006 by the United Nations General Assembly under resolution 61/105 which called upon fisheries management organisations to establish measures to assess, on the basis of best available scientific information, whether fishing activities would have significant adverse impacts on vulnerable marine ecosystems (VMEs), and to close areas where VMEs are known or are likely to occur, unless conservation and management measures have been established to prevent significant adverse impacts on these VMEs [In 2009, the UNGA reaffirmed this resolution]

5 What is a vulnerable marine ecosystem? In order to assist states and regional fisheries management organisations and arrangements (RFMO/As) in managing deep-sea fisheries and implementing the UNGA Resolution 61/105 a series of expert consultation meetings were held at request of COFI and FAO from 2006 to 2008 These meetings reviewed the topic, identified gaps in knowledge and capacity; clarified issues of vulnerability, destructive fishing and adverse impacts; drafted guidelines; obtained fishing industry perspective on draft guidelines; reviewed and adopted guidelines Resulted in International Guidelines for the Management of Deep-sea Fisheries in the High Seas (FAO, 2009) Guidelines include a definition of a vulnerable marine ecosystem (VME), how to identify them, and provide examples

6 Definition of a VME (FAO, 2009) 3.2 Vulnerable marine ecosystems 14. Vulnerability is related to the likelihood that a population, community, or habitat will experience substantial alteration from short-term or chronic disturbance, and the likelihood that it would recover and in what time frame. These are, in turn, related to the characteristics of the ecosystems themselves, especially biological and structural aspects. VME features may be physically or functionally fragile. The most vulnerable ecosystems are those that are both easily disturbed and very slow to recover, or may never recover. 15. The vulnerability of populations, communities and habitats must be assessed relative to specific threats. Some features, particularly those that are physically fragile or inherently rare, may be vulnerable to most forms of disturbance, but the vulnerability of some populations, communities and habitats may vary greatly depending on the type of fishing gear used or the kind of disturbance experienced. 16. The risks to a marine ecosystem are determined by its vulnerability, the probability of a threat occurring and the mitigation means applied to the threat.

7 Identifying VMEs Can you think of some identifying features criteria?

8 Identifying VMEs (FAO, 2009) i. Uniqueness or rarity an area or ecosystem that is unique or that contains rare species whose loss could not be compensated for by similar areas or ecosystems. These include: habitats that contain endemic species; habitats of rare, threatened or endangered species that occur only in discrete areas; or nurseries or discrete feeding, breeding, or spawning areas. ii. Functional significance of the habitat discrete areas or habitats that are necessary for the survival, function, spawning/reproduction or recovery of fish stocks, particular life-history stages (e.g. nursery grounds or rearing areas), or of rare, threatened or endangered marine species. iii. Fragility an ecosystem that is highly susceptible to degradation by anthropogenic activities. iv. Life-history traits of component species that make recovery difficult ecosystems that are characterized by populations or assemblages of species with one or more of the following characteristics: slow growth rates; late age of maturity; low or unpredictable recruitment; or long-lived. v. Structural complexity an ecosystem that is characterized by complex physical structures created by significant concentrations of biotic and abiotic features. In these ecosystems, ecological processes are usually highly dependent on these structured systems. Further, such ecosystems often have high diversity, which is dependent on the structuring organisms.

9 Examples of VMEs Examples you can think of?

10 Examples of VMEs (FAO, 2009) Examples of species groups, communities and habitat forming species (that may contribute to VMEs): i. certain coldwater corals and hydroids, e.g. reef builders and coral forest including: stony corals (Scleractinia), alcyonaceans and gorgonians (Octocorallia), black corals (Antipatharia) and hydrocorals (Stylasteridae); ii. some types of sponge dominated communities; iii. communities composed of dense emergent fauna where large sessile protozoans (xenophyophores) and invertebrates (e.g. hydroids and bryozoans) form an important structural component of habitat; iv. seep and vent communities comprised of invertebrate and microbial species found nowhere else (i.e. endemic).

11 Examples of VMEs (FAO, 2009) Examples of topographical, hydrophysical or geological features (that may support VMEs): i. submerged edges and slopes (e.g. corals and sponges); ii. summits and flanks of seamounts, guyots, banks, knolls, and hills (e.g. corals, sponges, xenophyphores); iii. canyons and trenches (e.g. burrowed clay outcrops, corals); iv. hydrothermal vents (e.g. microbial communities and endemic invertebrates); v. cold seeps (e.g. mud volcanoes for microbes, hard substrates for sessile invertebrates)

12 What has been done to protect VMEs? Number of mitigation measures have been considered and implemented by RFMO/As Example: South Pacific Regional Fisheries Management Organisation (SPRFMO) Penney et al (2009), Parker et al (2009)

13 SPRFMO Adopted an interim measure in 2007 to: limit bottom fishing to areas where such fishing is currently occurring; and where VMEs known or likely to occur implement measures to prevent significant adverse impacts on VMEs To do this they needed to: map the bottom trawl footprint, design a move-on rule based on at-sea identification of VME indicator taxa, and identify closed areas

14 The move-on rule concept?

15 SPRFMO Adopted an interim measure in 2007 to: limit bottom fishing to areas where such fishing is currently occurring; and where VMEs known or likely to occur implement measures to prevent significant adverse impacts on VMEs To do this they needed to: map the bottom trawl footprint, design a move-on rule based on at-sea identification of VME indicator taxa, and identify closed areas Analysis of trawl catch and effort data showed that fishing was unevenly distributed (low, moderate and high) and concentrated in 5 main areas (Lord Howe Rise, Challenger Plateau, West Norfolk Ridge, Three Kings Ridge, Louisville Seamount Chain)

16 Fishing footprint Penney et al (2009)

17 SPRFMO Adopted an interim measure in 2007 to: limit bottom fishing to areas where such fishing is currently occurring; and where VMEs known or likely to occur implement measures to prevent significant adverse impacts on VMEs To do this they needed to: map the bottom trawl footprint, design a move-on rule based on at-sea identification of VME indicator taxa, and identify closed areas Analysis of trawl catch and effort data showed that fishing was unevenly distributed (low, moderate and high) and concentrated in 5 main areas (Lord Howe Rise, Challenger Plateau, West Norfolk Ridge, Three Kings Ridge, Louisville Seamount Chain) Encounters with a possible VME can be detected when taxa that are indicators of a VME are caught in fishing trawls as part of the catch (i.e. satisfy the VME criteria, but are also identifiable by fisheries bycatch observers). A threshold weight was determined by using the median weight of historical catches for VME indicator taxa, and a scoring process developed to trigger the move-on rule.

18 Detecting VMEs and the move-on rule Parker et al. (2009)

19 SPRFMO Adopted an interim measure in 2007 to: limit bottom fishing to areas where such fishing is currently occurring; and where VMEs known or likely to occur implement measures to prevent significant adverse impacts on VMEs To do this they needed to: map the bottom trawl footprint, design a move-on rule based on at-sea identification of VME indicator taxa, and identify closed areas Analysis of trawl catch and effort data showed that fishing was unevenly distributed (light, moderate and heavy) and concentrated in 5 main areas (Lord Howe Rise, Challenger Plateau, West Norfolk Ridge, Three Kings Ridge, Louisville Seamount Chain) Encounters with a possible VME can be detected when taxa that are indicators of a VME are caught in fishing trawls as part of the catch (i.e. satisfy the VME criteria, but are also identifiable by fisheries bycatch observers). A threshold weight was determined using the median weight of historical catches for VME indicator taxa, and a scoring process developed to trigger the move-on rule. A three-tiered management approach was implemented that closed areas which were lightly fished, used the move-on rule in moderately fished areas, and allowed fishing in already heavily fished areas

20 Closures and 3-tier management measure Penney et al. (2009)

21 How well have mitigation measures worked? Penney & Guinotte (2013) undertook a cost:benefit analysis and an optimisation evaluation of the SPRFMO interim closures

22 How well have mitigation measures worked? Penney & Guinotte (2013) undertook a cost:benefit analysis and an optimisation evaluation of the SPRFMO interim closures Used fishing catch data for measuring industry interest in an area (cost), habitat suitability models to predict the likely occurrence of a VME indicator coral (adjusted for fishing in area) (benefit), and a 40% target for closure of areas in each fishing region that protected the highest average habitat suitability as a starting scenario (as per the target for the interim closures) before sequentially opening closed areas with the highest historical catch, and closing the block with the next highest habitat suitability until all areas in the fishing region were accounted for

23 What is a habitat suitability model?

24 Penney & Guinotte (2013)

25 How well are mitigation measures working? Penney & Guinotte (2013) undertook a cost:benefit analysis and an optimisation evaluation of the SPRFMO interim closures Used fishing catch data for measuring industry interest in an area (cost), habitat suitability models to predict the likely occurrence of a VME indicator coral (adjusted for fishing in area) (benefit), and a 40% target for closure of areas in each fishing region that protected the highest average habitat suitability is used as a starting scenario (as per the overall target for the interim closures) before sequentially opening closed areas with the highest historical catch, and closing the area with the next highest habitat suitability until all areas in the fishing region are accounted for This analysis generates reciprocal increasing cost and declining benefit curves, on which the cost (% retained catch) and benefit (% VME suitable habitat) of current closures can be plotted, and optimal scenarios identified

26 Average (adjusted) habitat suitability % Retained Catch Cost:benefit analysis of closures Optimisation step Penney & Guinotte (2013)

27 Optimisation of closures Penney & Guinotte (2013)

28 What is being done to improve mitigation? Use of presence-background habitat suitability models to predict likely occurrence of VMEs powerful addition to tools available to design protection measures. Vierod et al (2013) review recent advances and remaining issues.

29 Habitat suitability models Lophelia pertusa 1 ENFA ENFA km MaxEnt m MaxEnt 2013 Vierod et al (2013)

30 What is being done to improve mitigation? Use of presence-background habitat suitability models to predict likely occurrence of VMEs powerful addition to tools available to design protection measures. Vierod et al (2013) review recent advances and remaining issues. Among remaining issues are mismatch between predictions for the distribution of VME indicator taxa versus the distribution of the VME itself. Howell et al (2011) provide an example, and evidence for the future need for smaller-scale abundance based models that use data gathered by image and multibeam acoustic surveys.

31 VME-specific habitat suitability models Lophelia pertusa and Lophelia reef Howell et al (2011)

32 What is being done to improve mitigation? Use of presence-background habitat suitability models to predict likely occurrence of VMEs powerful addition to tools available to design protection measures. Vierod et al (2013) review recent advances and remaining issues. Among remaining issues are mismatch between predictions for the distribution of VME indicator taxa versus the distribution of the VME itself. Howell et al (2011) provide an example, and evidence for the future need for smaller-scale abundance based models that use data gathered by image and multibeam acoustic surveys. Continued questioning of the validity and criteria for the move-on rule still concerns about spreading the impact, and if used, the trigger thresholds which are based on unsubstantiated assumptions about what weight of bycatch indicates the presence of a VME. Auster et al (2011) suggest studies need to establish relationship between catch, catch efficiency and biomass of VME indicator taxa. Until then thresholds should be drastically reduced.

33 Gear efficiency and threshold weights 600 kg and % 6000 kg and 80,000 1% Auster et al (2011)

34 What is being done to improve mitigation? Use of presence-background habitat suitability models to predict likely occurrence of VMEs powerful addition to tools available to design protection measures. Vierod et al (2013) review recent advances and remaining issues. Among remaining issues are mismatch between predictions for the distribution of VME indicator taxa versus the distribution of the VME itself. Howell et al (2011) provide an example, and evidence for the future need for smaller-scale abundance based models that use data gathered by image and multibeam acoustic surveys. Continued questioning of the validity and criteria for the move-on rule still concerns about spreading the impact, and if used, the trigger thresholds which are based on unsubstantiated assumptions about what weight of bycatch indicates the presence of a VME. Auster et al (2011) suggest studies need to establish relationship between catch, catch efficiency and biomass of VME indicator taxa. Until then thresholds should be drastically reduced. Development of frameworks for a systematic approach to identifying and protecting VMEs these (e.g. Ardron et al in press) have resulted from concern about the approaches taken by different RFMO/As, and the perceived lack of progress in implementing effective and widespread protection for VMEs.

35 Systematic approaches 1. Comparatively assess potential VME indicator taxa and habitats in a region 2. Determine VME thresholds 3. Consider areas already known for their ecological importance 4. Compile information on the distributions of likely VME indicator species and habitats, with related environmental data 5. Develop predictive distribution models for VME indicator taxa and habitats 6. Compile known or likely fishing impacts 7. Produce a predicted VME naturalness distribution (areas of low cumulative impacts) 8. Identify areas of higher value to user groups 9. Conduct management strategy evaluations to produce trade-off scenarios 10. Review and re-iterate Ardron et al (in press)

36 What is the likely future fate of VMEs?