These pages are still under construction |
| Indicator | Attribute | Purpose | If restricted to taxa, list which ones | Ecosystem applicability | Identified capability | Biological classification level | Response variable | Drivers | Robustness |
|---|---|---|---|---|---|---|---|---|---|
| Ratios of tropic or habitat group - eg, biomass ratios of infauna/epifauna or pelagic/demersal or piscivore/planktivore | Trophic structure | Fisheries | Mostly temperate shelf to coastal inshore | Demonstrable | Ecosystem | Species-based, Trophodynamics | Anthropogenic, Trophodynamics | Potentially medium to high |
| Indicator examples | Current status and trends | Management objective/direction | Stakeholder/Public acceptability |
|---|---|---|---|
| Examples of how the indicator is used. | Pick one of the following:
| Pick one of the following:
| Pick one of the following:
|
| meta-study of pelagic:demersal (P:D) biomass ratios from 270 coastal marine systems around the world (mostly from North America, Europe and Australasia) | |||
The following is from Fulton et al 2004a -
In the past in those fields dealing with ecosystem health, indices focused on particular species or system components have been the primary tool used. While they do have some utility if the indicator species are chosen sensibly they can be found to be restrictive or lacking with regard to conveying the state of the system as a whole. It is obvious however, that extending a thorough species based analysis to a majority of the species in a system is unfeasible and an alternative method must be used. The ratios of different large-scale system-level components (e.g. phytoplankton vs zooplankton in general rather than specific species of phytoplankton or zooplankton) have been used effectively in water quality monitoring to capture higher-level ecosystem attributes such as structure and function (Xu et al. 2001a). In this way, the ratio of pelagic (planktivorous) fish species to demersal (or piscivorous) fish is a useful potential indicator of fished vs. unfished communities and is an indicator of mean trophic level and community structure. At this stage it is best established for temperate and tropical shelf to inshore coastal regions, but it requires further testing for tropical sand flats and deepwater slope regions (Caddy and Garibaldi 2000, Fulton unpub). The biological basis for the indicator is that unfished systems are generally more strongly dominated in terms of biomass by large bodied (usually demersal or piscivorous) species, which tend to have smaller planktivorous species as a component of their diet. Fishing typically targets larger species and with overfishing there is a fish-down of predators, creating a prey-release effect that allows small pelagics to increase in biomass and maintain their abundance by suppressing larval recruitment of the predatory species. The advantages associated with this type of trophic indicator is that they are conceptually simple and only require knowledge of the basic biology of the species used rather than diet data (Rochet and Trenkel 2003), which can be expensive and impractical to collect.
Infauna/epifauna (Inf:Epi) ratio
Research into pollution monitoring has found that the ratio of the biomasses of infauna and epifauna can be a strong indicator of disturbance (Shaw et al. 1983, Mendez 2002). As demersal fishing gear often disturbs or destroys epifauna, stirs the sediment and changes the detritus balance a shift from epifauna to infauna is anticipated. As a result the change in the biomass of these two ecosystem components may be a good indicator of the effects of fishing. Moreover, as epifauna is often the major habitat forming benthic group, this ratio may be a good habitat classification index too.
Pelagic/demersal (P:D) ratio
Whilst size-spectra analysis will also pick up changes in the ratio of pelagic:demersal abundance, because fishing typically alters the size structure of a community (Bianchi et al. 2000), the P:D ratio is a potentially simpler way of looking at the impacts of fishing at the trophic level.
...
It is noteworthy that pressures on the system other than fishing can affect the indicator. The ratio can also respond to changes (increase or decreases) in nutrient levels. Increases in nutrient levels can result from pollution or impacts of bottom fishing gear (which can mobilise nutrients from benthic sediments) and declines can be due to changed hydrodynamics or from impact mitigation schemes. An increase in nutrients will generally result in an increase of planktivores, whilst a decrease will result in a decline. As an example of both effects, when the Aswan dam was constructed in the Nile (Egypt), nutrient inputs into the Mediterranean declined causing an initial significant decline in sardines (pelagics) and a subsequent change in the P:D ratio. The ratio increased again when enriched drainage water reached the system many years later. (Caddy 2000). Both effects are illustrated in Figure 1.
Figure 1: The ratio of pelagic to demersal landings off the Nile Delta prior to and after the construction of the Aswan Dam. The rise in pelagics appears to be linked to enriched drainage water from the Delta (after Caddy 2000). (Figure provided by Fulton et al 2004a).
This indicator is very similar to the P:D ratio, except that it records the ratio of the biomass (or harvests) of piscivores to that of zooplanktivores, rather than planktivores to demersals. As with the P:D ratio, trends in this indicator are more useful than strict values and it is also susceptible to changes in market demand, capture technology (particularly if based on landings data rather than fishery independent data) and changes in environmental conditions (e.g. nutrient levels) (Caddy and Garibaldi 2000).
tropic structure
fisheries
The following is from Fulton et al 2004a -
The following is from Fulton et al 2004a -
Investigated for mostly temperate shelf to coastal inshore regions and some tropical reefs in Northern and Southern hemispheres (Fulton unpub, Caddy 2000). Not as established for tropical lagoonal systems or deepwater slope regions, though some work based on FAO data has incorporated deepwater sites (Caddy and Garibaldi 2000).
Is there any additional information that would be of interest in regards to the identified capability?
Otherwise can leave this section blank and just fill in the table instead.
Is there any additional information that would be of interest in regards to the biological classification?
Otherwise can leave this section blank and just fill in the table instead.
Is there any additional information that would be of interest in regards to the response variable?
Otherwise can leave this section blank and just fill in the table instead.
Is there any additional information that would be of interest in regards to ecological drivers?
If not can leave this section blank and just fill in the table instead.
The following is from Fulton et al 2004a -
Potentially medium to high: If the ratio is based on catch statistics alone, P:D and PS/ZP can be confounded by changes in targeting. Moreover, changes in productivity (which are often due to changes in nutrient levels) can also affect the system and these indicators. However, if based on fisheries independent data then they are potentially useful indicators of the overall trophic structure of the system.
The following is from Fulton et al 2004a -
In a meta-study of pelagic:demersal (P:D) biomass ratios from 270 coastal marine systems around the world (mostly from North America, Europe and Australasia) the P:D ratio for the entire system, not just the harvested components, was found to be consistently around the 0.15 – 0.3 level (Fulton unpub). Similarly, in a study concentrating on Port Phillip Bay, Victoria, the P:D ratio was 0.26 (Fulton unpub). These studies potentially provide some reference points for using the P:D indicator. If the ratio of small pelagics begins to increase beyond these sorts of levels, then ecosystem impacts are indicated. However, if the indicator is based on landings rather than fisheries independent biomass data the ratio may be much higher even in “healthy” systems. Thus, trends in the ratio are more informative than strict values.
define a standard set of management objectives?? ie from Indiseas
has it been used in a management strategy? if so how?
relationship to management strategies/ objectives
Acceptability with stakeholders
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:
Bianchi, G., H. Gislason, K. Graham, L. Hill, X. Jin, K. Koranteng, S. Manickchand-Heileman, I. Paya, K. J. Sainsbury, F. Sanchez, and K. Zwanenburg. 2000. Impact of fishing on size composition and diversity of demersal fish communities. ICES Journal of Marine Science 57: pp 558-71.
Caddy, J. F. 2000. Marine catchment basin effects versus impacts of fisheries on semi-enclosed seas. ICES Journal of Marine Science 57: pp 628-40.
Caddy, J. F., and L. Garibaldi. 2000. Apparent changes in the trophic composition of world marine harvests: the perspective from the FAO capture database. Ocean & Coastal Management 43: pp 615-55.
Mendez , N. 2002. Annelid assemblages in soft bottoms subjected to human impacts in the Urias estuary (Sinaloa, Mexico). Oceanologica Acta 25: 139-147
Rochet, M.-J., and V. M. Trenkel. 2003. Which community indicators can measure the impact of fishing? a review and proposals. Canadian Journal of Fisheries and Aquatic Science 60: pp 86-99.
Shaw, K.M., P.J.D. Lambshead, and H.M. Platt. 1983. Detection of pollution-induced disturbance in marine benthic assemblages with special reference to nematodes. Marine Ecology Progress Series 11: 195-202.
Xu, F.L., R.W. Dawson, S. Tao, J. Cao, and B.G. Li. 2001. A method for lake ecosystem health assessment: an Ecological Modeling Method (EMM) and its application. Hydrobiologia 443: 159-175.
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.
Please cite this page as:
<>
Page created by:
Last modified on:
Versions:
The macro included in this section of the template will automatically generate a list of reviewers who have viewed this page, and made comments.
Additional notes may include: personal communication, email feedback
Comment(s) made by: (see comments below)