Appendix A. A description of the input parameters needed to create an ECOPATH mass balance, their units, and empirical relations necessary to calculate them, following the ECOPATH user guide (Christensen et al. 2005).
TABLE A1. Input parameters needed to create an ECOPATH mass-balance.
|Biomass (B)||Average biomass per unit area in the habitat area where the group occurs||t/km2|
biomass ratio (P / B)
|Equivalent to the instantaneous rate of total mortality (Z)||y-1|
biomass (Q / B)
|Rate of intake of food by a group over time||y-1|
|Fraction of production that is further used in the system||†|
consumption (P / Q)
Ratio between production and consumption,
corresponds to gross food conversion efficiency
|Fecal fraction, part of consumption that returns to detritus||†|
|Detritus import||Rate of entry of detritus into the system||t/km2/y|
|Fishing landings||Represent the non-discarded part of the catch, expressed as flows||t/km2/y|
|Diets||Expressed as the fraction each prey contributes to the overall diet of a group||†|
TABLE A2. Empirical equations used to calculate productivity and consumption (Christensen et al. 2005), as well as quantifying Caridina nilotica* stocks (Goudswaard et al. 2006).
P / B = Z = M + F
P / B = K × (L∞ - L) / (L - L')
|Consumption||Q / B = 10C1 - W∞-C2 × 10-C3 × 10A × C4|
|Natural mortality||M = KC5 × L∞-C6 × C7|
|Fishing mortality||F = Y / B|
|Length||L∞ = Lt / (1 - e(t - t0))|
|Weight-length||W = a × Lb|
|FW = LC8 × e-C9 / C10|
TABLE A3. Parameters needed for the empirical equations.
|Z||Total mortality rate||y-1|
|M||Natural mortality rate||y-1|
|F||Fishing mortality rate||y-1|
von Bertalanffy growth function parameter expressing
rate at which asymptotic length is approached
|Lí||Length at entrance into fishery||cm|
|A||Tail aspect ratio parameter||†|
|Lt||Length at age t||Cm|
von Bertalanffy growth function parameter
expressing hypothetical age of a fish of length 0
|a||Scaling factor in W-L relationship||†|
|b||Exponent in W-L relationship||†|
TABLE A4. Constants used in empirical relations (Christensen et al. 2005).
|C1= 7.964||C6= 0.279|
|C2= 0.204||C7= 4.439|
|C3= 6.583||C8= 2.7|
|C4= 0.083||C9= 4.876|
Christensen, V., C. Walters, and D. Pauly. 2005. ECOPATH with ECOSIM: a user's guide. Fisheries Centre, University of British Columbia, Vancouver.
Goudswaard, K. P. C., F. Witte, and J. H. Wanink. 2006. The shrimp Caridina nilotica in Lake Victoria (East africa), before and after the Nile perch increase. Hydrobiologia 563:31–44.