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The international bottom trawl survey used stratification based on depth. There is evidence that in some areas, bottom sediment type makes a significant difference in fish populations, so characteristics of the seabed will be incorporated into future stratification designs. Stratification can become a confounding factor in samples of several different species where the species have different spatial distribution characteristics. Preliminary analysis is need to know how to stratify when surveying several species.
(this is where I got bored of reading most of the document, and it is 174 pages, so the rest is just a summary of a skim reading).
There is a detailed graphic on printed page 24 that describes how to chose what type of survey to use to be continued)get good population estimates.
Starting on printed page 39 the report talks about integrating trawl survey data and SONAR data.
Printed page 49 starts talking about estimating population parameters from survey data.
Recommendation
- The spatial distribution of the fish should be considered when designing and