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A new optimal foraging model predicts habitat use by drift‐feeding stream minnows
Author(s) -
Grossman G. D.,
Rincon P. A.,
Farr M. D.,
Ratajczak R. E.
Publication year - 2002
Publication title -
ecology of freshwater fish
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 55
eISSN - 1600-0633
pISSN - 0906-6691
DOI - 10.1034/j.1600-0633.2002.110102.x
Subject(s) - foraging , habitat , predation , optimal foraging theory , range (aeronautics) , environmental science , ecology , position (finance) , mathematics , biology , materials science , finance , economics , composite material
– There is substantial need for models that accurately predict habitat selection by fishes for purposes ranging from the elaboration of ecological theory to the preservation of biodiversity. We have developed a new and highly tractable optimal foraging model for drift‐feeding fishes that is based on the profitability of occupying varying focal‐point velocities in a stream. The basic model can be written as: I x = ( E x * P x ) = {( D * A * V ) * [1/(1 + e ( b + cV ) )]} − S x , where: (1) I x is the net energy intake at velocity x ; (2) E is prey encounter rate; (3) P is prey capture success rate which can be modelled as 1/(1 + e ( b + cV ) ) where b and c are fitting constants from the prey capture success curve; (4) D is the energy content of prey (J/m 3 ) in the drift; (5) A is the visual reactive area of the fish; (6) V is velocity (cm/s); and (7) S is the cost of maintaining position (J/s). Given that D , A and S can be considered constant over the range of velocities occupied by these fishes, the model reduces to e ( b + cV ) = 1/( cV − 1) which we solved iteratively to yield an optimal focal‐point velocity for species in each sample. We tested the model by comparing its predictions to the mean focal‐point velocities (i.e. microhabitats) occupied by four species of drift‐feeding minnows in two sites in a stream in North Carolina, USA. The model successfully predicted focal‐point velocities occupied by these species (11 out of 14 cases) in three seasonal samples collected over 2 years at two sites. The unsuccessful predictions still were within 2 cm/s of the 95% confidence intervals of mean velocities occupied by fishes, whereas the overall mean deviation between optimal velocities and mean fish velocities was small (range = 0.9 and 3.3 cm/s for the warpaint shiner and the Tennessee shiner, respectively). Available focal‐point velocities ranged from 0–76 to 0–128 cm/s depending on site and season. Our findings represent one of the more rigorous field tests of an optimal foraging/habitat selection model for aquatic organisms because they encompass multiple species and years, and for one species, multiple sites. Because of the ease of parameterization of our model, it should be readily testable in a range of lotic habitats. If validated in other systems, the model should provide critical habitat information that will aid in the management of riverine systems and improve the performance of a variety of currently used management models (e.g. instream flow incremental methodology (IFIM) and total maximum daily load calculations (TMDL)).