I have 4 independent variables (types of enrichment, types of tanks, mating pairs, strain of zebrafish) (nominal scale) with 1 dependent variable (fecundity of zebrafish/embryos laid) (scale data). what type of statistical test should i use?
I would use a mixed-factors analysis of variance if all your independent variables are nominal. If mating pair is your unit of variance (number of replicates = X number of mating pairs), I include mating pair as a covariate rather than a typical independent variable, since differences between matings would be a quality control issue rather than a specific hypothesis to test.