Swimbladder Allometry of Selected Midwater Fish Species

: The study examines the relationship of fish standard length to swimbladder length, width, and volume. The intra- and inter-specific variation is studied in over 1600 selected mesopelagic fish specimens belonging to 55 species from 9 families. These species are believed to account for most of the volume reverberation occurring throughout a large part of the Sargasso Sea. Regression equations presented in the report allow calculation of swimbladder volumes directly from measurements of fish standard length for 55 species of midwater fish. Additional equations allow the calculation of swimbladder length and width from measurements of the standard lengths of these same species. It is shown that for 40 species, bladder volume increases with increasing standard length. Slopes of the regression lines for 14 species are shown to be insignificant from zero. For one species, bladder volume decreases slightly with increasing standard length. Results of the study demonstrate that equations currently in use overestimate the volumes of the swimbladders and thus acoustic cross sections of many midwater fish species.