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Indicator summary

Summary of indicator structure and function

IndicatorAttributePurposeIf restricted to taxa, list which onesEcosystem applicabilityIdentified capabilityBiological classification levelResponse variableDriversRobustness
Rates of anatomical damageHabitat structure and conditionFisheriesBenthic communitiesBenthic northern hemisphere boreal, temperate shelf and slope systems.DemonstrableCommunity

Trophodynamics, Environmental

AnthropogenicLow to high

Examples of how the indicators is used for ecosystem management and ecosystem status and trends

Indicator examplesCurrent status and trendsManagement objective/directionStakeholder/Public acceptability
arm loss or damage in seastars   
damaged annual growth rings in some mollusc species   
severe sediment displacement, with up to a 75% reduction in density of individuals of Anthoza and Malacostraca recorded in a meta study of trawl impacts on benthos   

Definition and/or background

The following is from Fulton et al 2004a -

A number of potential indicators of the effects of fishing have been identified from among benthic groups and communities. The types of indicators include:

  • percent of damaged individuals with trawl effort;
  • mean proportion (%) of a population with damage after trawling;
  • rate of loss (i.e. arm loss for seastars);
  • relative incidence of shell scars after trawling; and
  • relative damage.

Some of these are more useful as indicators of relative levels of F rather than impacts of fishing, but they are still useful as they allow for the estimation of relatively local fishing pressure (even when available data is on a much broader scale) (Rogers et al. 2001).

Benthic studies on the effects of fishing have shown that certain taxa are susceptible to damage by mobile bottom fishing gear, due to factors such as life history traits, habitat niche or mobility (Bergman and Hup 1992; Jennings and Kaiser 1998, Prena et al.1999, Eleftheriou 2000, Collie et al. 2000, Ramsay et al. 2001, Stobutzki et al. 2001). Damage has been shown to be significantly higher for these indicator organisms in trawled vs untrawled areas. ...

Some groups sustain measurable non-fatal anatomical damage, which may be useful surrogates for determining the intensity of benthic habitat disturbance cause by mobile fishing gear. Examples of measurable damage are arm loss or damage in seastars (Bergman and Hup 1992, Jennings and Kaiser 1998, Prena et al. 1999, Rogers et al. 2001); damaged annual growth rings in some mollusc species (Witbaard and Klein 1994 in Jennings and Kaiser 1998, Jennings et al. 2001). Other experiments and surveys show correlations between trends in density and abundance with mechanical habitat disturbance such as severe sediment displacement, with up to a 75% reduction in density of individuals of Anthoza and Malacostraca recorded in a meta study of trawl impacts on benthos (Auster and Langton 1999, Collie et al. 2000). 


Habitat structure and condition


Benthic groups and communities, Fisheries

Data required

The following is from Fulton et al 2004a -

  • Direct counts of damaged individuals from trawl catch/trawl effort
  • Habitat classification for each taxa
  • Counts of damaged surrogate species in stomach samples of fish after trawling
  • Baseline data on incidence of damage pre-trawling
  • Counts of growth rings in susceptible species
  • Identification of species vulnerable to trawl damage
  • Fishing effort (temporal; spatial)

For seastar damage:

  • Counts of damaged seastar arms at time of catch and between 2-8 days following
  • Counts of damaged seastar arms prior to trawling (baseline)
  • Fishing effort (i.e. tow duration and number, and/or area swept)

Ecosystem applicability

The following is from Fulton et al 2004a -

Rates of damage have been demonstrated primarily in studies of benthic northern hemisphere boreal, temperate shelf and slope systems, particularly for stable sediments. However, it should be more widely applicable across marine systems.


The following is from Fulton et al 2004a -

Low to high, depending on species chosen: Has potential, providing the right species are selected and reference area data on natural rate of damage is collected. The indicators have proven robust at least for the study of Arctica islandica, where three different methods of investigation of trawl impacts in the same area (rates of damage to direct catch, rates of damaged growth rings, counts of damaged A. islandica in stomach contents of cod immediately after trawling) independently tested the correlation of damage with trawling damage to habitats. The results indicated the potential for using rate of damage in sensitive species especially in stable substrates as indicators of anthropogenic damage to benthic habitat. An advantage of using bivalve molluscs is that long-lived species provide a disturbance history of a particular area over a number of decades (Jennings et al. 2001).  However, the use of such indicators will probably be time consuming, costly and require baseline information on natural rates of damage to surrogates. Moreover, studies indicate that the use of infaunal indicators are more likely to be quantified in stable sediments (e.g. coarse gravel/sand not usually subject to natural disturbance) than mobile sediments (Jennings and Kaiser 1998), and impacts are also more likely to be detected in areas previously unexposed or only recently exposed to fishing. There is more potential for the use of starfish, as they are globally distributed and so they are potential indicator species of damage to benthic habitats in a wide range of marine ecosystems. It would be useful to investigate this indicator in deep-water trawl fisheries. A variety of other sensitive benthic taxa have been identified as potential indicators in other marine systems including tropical, southern temperate, boreal, northern temperate (Sainsbury 1987, Auster et al. 1996, Jennings and Kaiser 1998, Collie et al. 1997, Collie et al. 2000, Stobutzski 2001) and similar investigations to relate rates of damage/mortality to fishing effort could be undertaken. For all of these indicators however, most authors have raised the need for reference areas to provide baseline and monitoring reference points. Overall, the main limitations to using this approach are that the method is time consuming, though relatively simple, and requires baseline data on rates of natural damage preferably from reference areas. In addition, this indicator is not a final indicator of the effects of fishing on a system, but is only an indicator that assists in identifying the magnitude of fishing pressure on the system.

Current status and trends

The following is from Fulton et al 2004a -

For example, in an experimental study of trawl impacts on the benthos of Grand Banks in Newfoundland, Prena et al. (1999) analysed the effect of trawling on individual species and found that there were statistically significant effects of both trawling and year on rates of damage. It was also found that percent damage was significant for individual echinoderms: sand dollars (Echinarachinius parma) at 8-23% (p < 0.0001 ), a sea urchin, (Strongylocentrotus pallidus) at 1-5% (p < 0.0001 ) and a brittle star (Ophiura sarsi) (p < 0.0001).

Relative damage

An attempt to relate levels of damage with levels of fishing intensity has been made using seastar arm loss data from the United Kingdom for Asteria rubens (Ramsay et al. 2001) and some crude reference points emerge from this particular study:

EffortArea sweptDamage
Light effort10% area swept  0.26-1.8% arm loss
Heavy effort

5 times/yr   

13-93% arm loss

Such reference points may be useful for ascertaining fishing effort at small spatial scales.


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.

References that Fulton et al uses for this indicator:

Auster, P. J., and R. W. Langton. 1999. The effects of fishing on fish habitat. American Fisheries Society Symposium  22: pp 150-187.

Auster, P. J., R. J. Malatesta, R. W. Langton, L. Watling, P. C. Valentine, C. Lee, S. Donaldson, E. W. Langton, A. N. Shepard, and I. G. Babb. 1996. The impacts of mobile fishing gear on seafloor habitats in the Gulf of Maine (Northwest Atlantic); implications for conservation of fish populations. Reviews in Fisheries Science 4, no. 2: pp 185-202.

Bergman, M. J. N., and M. Hup. 1992. Direct effects of beamtrawling on macrofauna in a sandy sediment in the southern North Sea. ICES Journal of Marine Science 49: pp 5-11.

Collie, J. S., G. A. Escanero, and P. C. Valentine. 1997. Effects of bottom fishing on the benthic megafauna of Georges Bank. Marine Ecology Progress Series 155: pp 159-72.

Collie, J. S., S. J. Hall, M. J. Kaiser, and I. R. Poiner. 2000. A quantitative analysis of fishing impacts on shelf-sea benthos. Journal of Animal Ecology 69: pp 785-98.

Eleftheriou, A. 2000. Marine benthos dynamics: environmental and fisheries impacts: introduction and overview. ICES Journal of Marine Science 57: pp 1299-302.

Jennings, S., and M.J. Kaiser. 1998. The effects of fishing on marine ecosystems. Advances in Marine Biology 34: pp 201-351.

Jennings, S., M.J. Kaiser, and J.D. Reynolds. 2001.  Marine fisheries ecology.,. 417 p . London: Blackwell Science .

Prena, J., P. Schwinghamer, T. W. Rowell, D. C. Jr. Gordon, K. D. Gilkinson, W. P. Vass, and D. L. McKeown. 1999. Experimental otter trawling on a sandy bottom ecosystem of the Grand Banks of Newfoundland: analysis of trawl bycatch and effects on epifauna. Marine Ecology Progress Series 181: pp 107-24.

Ramsay, K., M. Bergmann, L. O. Veale, C. A. Richardson, M. J. Kaiser, S. J. Vize, and S. W. Feist. 2001. Damage, autotomy and arm regeneration in starfish caught by towed demersal fishing gears. Marine Biology 138: pp 527-36.

Rogers, S. I., D. Maxwell, A. D. Rijnsdorp, U. Damm, and W. Vanhee. 1999. Fishing effects in northeast Atlantic shelf seas: patterns in fishing effort, diversity and community structure. IV. Can comparisons of species diversity be used to assess human impacts on demersal fish faunas?  Fisheries Research 40: pp 135-52.

Sainsbury, K. J. 1987. Assessment and management of the demersal fishery on the continental shelf of northwestern Australia. In: Tropical snappers and groupers: biology and fisheries management. Editors J. J. Polovina, and S. Ralston, Chapter 10-465-502. Ocean Resources and Marine Policy Series. Boulder, Colorado: Westview Press.

Stobutzki, I., M. Miller, and D. Brewer. 2001. Sustainability of fishery bycatch: a process for assessing highly diverse and numerous bycatch. Environmental Conservation 28, no. 2: pp 1-15.

Witbaard, R., and R. Klein. 1994. Long-term trends on the effects of the southern North Sea beamtrawl fishery on the bivalve mollusc Arctica islandica L. (Mollusca, bivalvia). ICES Journal of Marine Science 51: pp 99-105.

Background reading

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.



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