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Indicator summary
Summary of indicator structure and function
Indicator | Attribute | Purpose | If restricted to taxa, list which ones | Ecosystem applicability | Identified capability | Biological classification level | Response variable | Drivers | Robustness |
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Abundance | Community structure, trophic Trophic structure, habitat Habitat structure and condition | All species |
| Should be applicable for al ecosystems | DemonstrableAspirational | Community, Ecosystem | Species-based | Trophodynamics?Anthropogenic | Medium to high |
Examples of how the indicators is used for ecosystem management and ecosystem status and trends
Indicator examples | Current status and trends | Management objective/direction | Stakeholder/Public acceptability |
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Examples of how the indicator is used. | Pick one of the following: | Pick one of the following: | Pick one of the following: |
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Definition and/or background
The following is from Fulton et al 2004a -
Changes to habitat can be reflected by changes to the communities, which inhabit them. For example, changes to species composition have been demonstrated to be a useful measure of fishing impact on habitats (Sainsbury 1987, Bianchi et al. 2000, Jennings and Kaiser 1998, Jennings et al. 2001). For example, studies in the southern North Sea revealed that increased abundance of small invertebrates indicated re-suspension of infaunal benthic organisms due to pressure waves from beam trawling (Bergman and Hup 1992, Gilkinson et al. 1998).
Attribute
Community structure, trophic structure, habitat structure and condition
Taxa
All taxa
Data required
The following is from Fulton et al 2004a -
Long time-series of (or data from fished and unfished areas on):
- Abundance
- Biomass
- Length-frequency data
- Habitat characteristics (optional)
- Diet composition (optional)
Ecosystem applicability
The following is from Fulton et al 2004a -
Should be applicable to all ecosystems.
Robustness
The following is from Fulton et al 2004a -
Medium to high: Utility and robustness depends on the quality of the data available and the methodology used. There are some limitations in that the relative abundance (e.g. taxa in fished and unfished sites) may not reveal consistent directional changes due to disturbance. To overcome this some authors have applied Wilcoxon’s paired sign test for clarification (Kaiser and Spencer 1996). If using long-term time-series the degree of change may be underestimated if the time-series does not begin until there have already been substantial changes in the area being monitored. In addition, other environmental or anthropogenic pressures on a system (e.g. ENSO or eutrophication) could also affect abundance.
Current status and trends
The following is from Fulton et al 2004a -
Decreased abundance
In experimental studies of trawling on stable sediments at depths of between 27- 40m in the Irish Sea, Kaiser and Spencer (1996) recorded that the number of species and individuals was reduced by two and threefold respectively (Jennings and Kaiser 1998). Elsewhere, scallop dredging in the Clyde Sea area (Scotland) led to a 70% reduction in abundance (by number) of counts of live maerl (coralline algae) thalli with no sign of recovery after 4 years (Hall-Spencer and Moore 2000). Maerl beds form extremely long-lived complex sediments and create areas of high biodiversity, so their loss can have significant community-level impacts. In Australia it was found that the abundance of fish and small invertebrates increased in closed areas and decreased in fished areas of the North West shelf (Sainsbury et al. 1997). The fish community changed over an 11 yr period from larger ambush predators (Lutjanus and Lethrinus), which inhabit structurally complex habitats dominated by large epibenthic fauna such as sponges, to smaller fish typical of open habitats (Saurida and Nemipterus). A model relating the fish species abundance to habitat structure showed that this change was most likely due to destruction of large epibenthic sponges, alcyonarians and gorgonians by trawl gear that provided cover, shelter and food for the displaced species. (Sainsbury et al. 1997). Another study considering fish community was carried out on the Georges Banks, North Atlantic. It was found that the fish community structure changed from gadoids and flounders to small elasmobranchs (dogfish and skates) (Fogarty and Murawski 1998). This change was an indirect effect of reduction of the abundance of gadoids and flounders by fishing, which in turn reduced competition for the replacement species. The second order consequence may be an impact on foraging seabirds and mammals which utilised the gadoid and flounder as prey.
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If time-series are used to detect vulnerable species, rather than comparisons with unfished areas, then long time-series data are required. An example of this approach is from the North Sea. In an extended study on a data series to describe diversity changes between 1925-1996 in Scottish North Sea using Hill’s indices and k-dominance curves (Greenstreet et al., 1999), it was found that species diversity declined in areas of high fishing intensity. It was also found that fishing effects caused the largest decrease in abundance in skates and rays, which are K-selected species that are highly vulnerable to exploitation (Greenstreet et al., 1999). Studies of trawling impacts in the Dutch sector of the North Sea showed that overall, trawling resulted in lower densities of vulnerable species and a greater abundance in opportunistic species (Eleftheriou 2000). For fish, a study aimed at ranking 411 tropical bycatch species of 99 families in the Australian Northern Prawn Fishery with respect to their vulnerability to trawling (Stobutzki et al. 2001) found that the most vulnerable species (high susceptibility to capture and mortality) were mainly benthic or demersal, closely associated with the sea floor, from primarily soft or muddy sediments, and with a diet that includes prawns. Mortality or injury rates of vulnerable fish species may be potential measures of trawl impacts on these species, but it needs further testing. Vulnerability rankings have been determined for bycatch fish and catch thresholds for the vulnerable fish could be determined using the q jeopardy model (Pope et al), which could provide an index of catch limits for the species or aggregate of species.
Attribute
Community structure, trophic structure, habitat structure and condition
Purpose
Taxa
All taxa
Data required
The following is from Fulton et al 2004a -
Long time-series of (or data from fished and unfished areas on):
- Abundance
- Biomass
- Length-frequency data
- Habitat characteristics (optional)
- Diet composition (optional)
Ecosystem applicability
The following is from Fulton et al 2004a -
Should be applicable to all ecosystems.
Identified capability
...
Biological classification level
...
Response variable
...
Drivers
...
Robustness
The following is from Fulton et al 2004a -
Medium to high: Utility and robustness depends on the quality of the data available and the methodology used. There are some limitations in that the relative abundance (e.g. taxa in fished and unfished sites) may not reveal consistent directional changes due to disturbance. To overcome this some authors have applied Wilcoxon’s paired sign test for clarification (Kaiser and Spencer 1996). If using long-term time-series the degree of change may be underestimated if the time-series does not begin until there have already been substantial changes in the area being monitored. In addition, other environmental or anthropogenic pressures on a system (e.g. ENSO or eutrophication) could also affect abundance.
Current status and trends
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Management objective/direction
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Stakeholder?Public acceptability
Acceptability with stakeholders?
* by all stakeholder
* by the public
* understandable to the stakeholders
References
Fulton, E.A., Smith, A.D.M., Webb, H., and Slater, J. (2004a) Ecological indicators for the impacts of fishing on non-target species, communities and ecosystems: Review of potential indicators. AFMA Final Research Report, report Number R99/1546.
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Fulton, E.A., Fuller,M., Smith, A.D.M., and Punt, A. (2004) Ecological indicators of the ecosystem effects of fishing: Final report. AFMA Final Research Report, report Number R99/1546.
Other references that can be used to update this page
Other references that SD has found that would be useful to update the indicator referred to on this page.
Citation
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Reviewers
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Fogarty, M. J., and S. A. Murawski. 1998. Large-scale disturbance and the structure of marine systems: fishery impacts on Georges Bank. Ecological Applications 8, no. 1, Supplement: pp S6-S22.