| 5 | | 1. Predator-prey cycles and related multi-trophic level patterns; |
| 6 | | |
| 7 | | 1. System simplification (loss of biomass pools due to competition/predation effects); |
| 8 | | |
| 9 | | 1. Stock-recruitment instabilities (cyclic or erratic changes in recruitment and stock size for split pool groups); |
| 10 | | |
| 11 | | 1. Numerical ‘chatter’ in time solutions (mainly in Ecospace). |
| | 4 | 1. Predator-prey cycles and related multi-trophic level patterns;[[BR]] |
| | 5 | 1. System simplification (loss of biomass pools due to competition/predation effects);[[BR]] |
| | 6 | 1. Stock-recruitment instabilities (cyclic or erratic changes in recruitment and stock size for split pool groups);[[BR]] |
| | 7 | 1. Numerical ‘chatter’ in time solutions (mainly in Ecospace). |
| 19 | | 1. Risk-sensitive prey behaviours:Prey may spend only a small proportion of their time in foraging arenas where they are subject to predation risk, otherwise taking refuge in schools, deep water, littoral refuge sites, etc.; |
| 20 | | |
| 21 | | 1. Risk-sensitive predator behaviours (the ‘three to tango’ argument):Especially if the predator is a small fish, it may severely restrict its own range relative to the range occupied by the prey, so that only a small proportion of the prey move or are mixed into the habitats used by it per unit time; in other words, its predators may drive it to behave in ways that make its own prey less vulnerable to it; |
| 22 | | |
| 23 | | 1. Size-dependent graduation effects:Typically a prey pool represents an aggregate of different prey sizes, and a predator can take only some limited range of sizes, limited vulnerability can represent a process of prey graduation into and out of the vulnerable size range due to growth. Size effects may of course be associated with distribution (predator-prey spatial overlap) shifts as well; |
| 24 | | |
| 25 | | 1. Passive, differential spatial depletion effects:Even if neither prey or predator shows active behaviours that create foraging arena patches, any physical or behavioural processes that create spatial variation in encounters between ''i'' and ''j'' will lead to local depletion of'' i'' in high risk areas and concentrations of i in partial predation ‘refuges’ represented by low risk areas. ‘Flow’ between low and high risk areas (''v,,ij,,'') is then created by any processes that move organisms. |
| | 15 | 1. Risk-sensitive prey behaviours: Prey may spend only a small proportion of their time in foraging arenas where they are subject to predation risk, otherwise taking refuge in schools, deep water, littoral refuge sites, etc.;[[BR]] |
| | 16 | 1. Risk-sensitive predator behaviours (the ‘three to tango’ argument):Especially if the predator is a small fish, it may severely restrict its own range relative to the range occupied by the prey, so that only a small proportion of the prey move or are mixed into the habitats used by it per unit time; in other words, its predators may drive it to behave in ways that make its own prey less vulnerable to it;[[BR]] |
| | 17 | 1. Size-dependent graduation effects: Typically a prey pool represents an aggregate of different prey sizes, and a predator can take only some limited range of sizes, limited vulnerability can represent a process of prey graduation into and out of the vulnerable size range due to growth. Size effects may of course be associated with distribution (predator-prey spatial overlap) shifts as well;[[BR]] |
| | 18 | 1. Passive, differential spatial depletion effects: Even if neither prey or predator shows active behaviours that create foraging arena patches, any physical or behavioural processes that create spatial variation in encounters between ''i'' and ''j'' will lead to local depletion of'' i'' in high risk areas and concentrations of i in partial predation ‘refuges’ represented by low risk areas. ‘Flow’ between low and high risk areas (''v,,ij,,'') is then created by any processes that move organisms. |
| 31 | | Numerical instabilities (chatter, oscillations of growing amplitude) occur mainly in Ecospace. They are avoided in Ecosim by only doing time dynamic integration of change for pools that can change relatively slowly. In Ecospace, the only remedy for chatter is to reduce the prediction time step (from 12/year default value, sometimes very low values such as 0.05 year are required for stability). In extreme cases, it might be necessary to ‘fool’ Ecosim/Ecospace by implicitly moving to a shorter time step for all dynamics, which you can do by dividing every Ecopath input time rate (''P/B, Q/B'') with the same factor. |
| | 24 | Numerical instabilities (chatter, oscillations of growing amplitude) occur mainly in Ecospace. They are avoided in Ecosim by only doing time dynamic integration of change for pools that can change relatively slowly. In Ecospace, the only remedy for chatter is to reduce the prediction time step (from 12/year default value, sometimes very low values such as 0.05 year are required for stability). In extreme cases, it might be necessary to ‘fool’ Ecosim/Ecospace by implicitly moving to a shorter time step for all dynamics, which you can do by dividing every Ecopath input time rate (''P/B, Q/B'') with the same factor. |
