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Determinants of anadromy and residency:


Notes:

Determinants of anadromy and residency in a sympatric population include the following. 1.) Degree of sympatry and interbreeding. This factor is directly related to the previously described overlap in the spatial and temporal distribution. It can also be influenced by the abundance and sex ratios of both ecotypes. 2- Genetic inheritance of predisposition. 3. Environmental factors directly affectiing size and growth rates. This introduces the possibility of environmental conditions favoring production of one ecotype over the other related to a watersheds hydrology, annual temperature profiles and food availabilty during critical growth windows. 4- Relative productivity specific to anadromous and resident ecotypes. For steelhead, this includes fecundity,progeny abundance, migrant survival rates to and from the ocean and ocean productivity. For resident trout, this includes fecundity, progeny abundance and survival in the freshwater environment. So, when attempting to model production of both life history types, how many pieces of the puzzle to we have and what are the constraints related to these 4 elements. I’ll be the first to tell you that the complexity and interactions related to elements 2 and 3 surpasses our ability to accurately model these elements at the finite resolution that would be required. So these two elements are condensed into explicit assumptions for both fidelity and hybrid mating crosses related to their proportions of progeny ecotype production. On the contrary, several experiments exist that looked at the relative production and or migrant survival of both ecotype progeny for all potential mating crosses. So from the literature, heuristic relationships can be established for our modeling purposes. The strength of this model lyes in emperical data that we have specific to the demographics both ecotypes and characterization of the productivity and capacity of the freshwater environment. This enables us to build a lifecycle model with interactions at multiple life stages between the two ecotypes.