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| 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 | Tropic Trophic structure | fisheriesFisheries | Mostly temperate shelf to coastal inshore | Demonstrable | Ecosystem | trophodynamics | trophodynamicsSpecies-based, Trophodynamics | Anthropogenic, Trophodynamics | Potentially medium to high |
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| 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:
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| meta-study of pelagic:demersal (P:D) biomass ratios from 270 coastal marine systems around the world (mostly from North America, Europe and Australasia) | |||
Definition and/or background
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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 51.5.
Figure 5.51: 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). need to add figure 5.5(Figure provided by Fulton et al 2004a).
Piscivore/planktivore (PS/ZP) ratio
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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).
Identified capability
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.
Biological classification level
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Response variable
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Drivers
Is there any additional information that would be of interest in regards to ecological drivers?
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Robustness
The following is from Fulton et al 2004a -
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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.
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