Defining survey objectives
The first step is to clearly define survey objectives (e.g., Pollock et al. 2002). For fisheries acoustic surveys, the objective is most often to estimate the relative or total fish abundance. Both of these objectives involve defining the area from which the samples will be taken so that the population will be fully and fairly represented.
In addition to the objective of estimating abundance, the researcher may also be interested in:
monitoring fish behavior;
measuring movement from one area to another, or;
contrasting density of fish in one habitat vs. another
Different objectives may require some subtle, and some not so subtle, changes to the survey design. These design components may compete with one another for survey and analysis time and may ultimately influence statistical confidence in the estimate.