Great book on lots of fisheries "how to and what it means" questions. \:\) Check it out here

http://www.fisheries.org/html/publications/catbooks/x55029.shtml

B. R. Murphy and D. W. Willis, editors

Summary
A comprehensive reference volume of modern sampling and data collection methods
in fisheries science for students and professionals. This new edition includes two
new chapters: one on statistical considerations in fisheries sampling and the other
on sampling of invertebrate organisms. All other chapters have been thoroughly rewritten
to include innovations of the last decade. Each chapter provides a description of various
approaches and techniques, with a review of applications, advantages and limitations.
A comprehensive glossary of terms has been added.