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The model inputs from the various data sources were used as initial estimates but were adjusted in many cases to obtain a balanced model, that is, one in which the estimated inflows and outflows were equal for every functional group.

Adjustments included changes to input biomass estimates, diet composition and physiological rates to ensure that not only biomass balance but also various other model constraints were satisfied. The final, balanced model can be downloaded here.

A thorough examination of each ecopath model solution requires a variety of consistency checks, sensitivity tests and comparisons with model results from other similar or related ecosystems to establish an appropriate degree of confidence in model results. Although much work has been completed in this regard on the LAPE model, further examination is warranted before any quantitative model results are used to specify management decisions.

The details of the inputs, adjustments and testing of the LAPE Ecopath model are documented in LAPE Technical Document No. 2.

Click here to download Model


Sample model outputs


A 'map' of the trophic linkages in the LAPE Ecopath model shows the 31 functional groups joined by several types of interaction linkages. This example highlights the direct trophic linkages between flyingfish and all other functional groups, with consumption by flyingfish in red and predation on flyingfish in black. The remaining grey linkages do not involve flyingfish directly. Numeric values for each interaction can be included, in this example only the diet component imported from outside the LAPE is shown.

 

Flow diagrams represent the relative magnitude of each biomass flow in the balanced model by the thickness of the line, where consumption is coloured blue, predation is red and fisheries are green. Samples here include small coastal pelagics, dolphinfish and shallow-diving cetaceans.

Small Coastal Pelagics
Small Coastal Pelagics
Dolphin Fish
Dolphin Fish
Shallow-Diving Cetaceans
Shallow-Diving Cetaceans

 

Sources of mortality

The dominance of predation mortality in the system is evident from mortality estimates for regional large pelagic species. All these species are of commercial importance, however fishing mortality is greater for some groups, e.g., wahoo, blackfin tuna, mackerels, dolphinfish compared to others (fishing mortality is blue, predation mortality is magenta and other mortality is yellow).

 

Predation consumption of selected prey

Based on the diet composition information, the population size and the metabolic demands of a given species the Ecopath model provides estimates of the consumption rate of prey species by predators. Consumption rates, in units of metric tonnes, per year, per square kilometer, can be converted to total tonnes per year by multiplying by 610,000. Notable in the consumption estimates is the very high fraction of cannibalism in the dolphinfish diet.

 
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