Aspects of the Biology of the Common Snook, Centropomus undecimalis (Bloch) of Southwest Florida

Volpe, Alfred

1. Competition between commercial and sport fishermen of the state of Florida for the common snook motivated the State Board of Conservation to request The Marine Laboratory of the University of Miami to study this fish. Marshall (1958) made a study of the snook fishery and some aspects of its biology. This paper deals with those aspects not studied in detail by Marshall, mainly migration, age and growth. 2. Migration was studied by means of a tagging program in which different types of tags and methods of capture were used. 3. A total of 2,068 snook were tagged in eighteen salt and brackish water areas of south Florida, and sixty-one, or 2.9 per cent, were recaptured within 333 days after they were released. 4. The beach seine pro;ed the most efficient gear for capturing large quantities. During the spawning season, and the Petersen disk tag was the most efficient of the three tags used, although it caused some tissue damage. 5. The use of sport fishermen as taggers proved unsatisfactory, due mostly to inconsistencies in measuring and recording lengths of snook. 6. The catch of tagged snook was about equally divided between sport and commercial fishermen. 7. A nonmigratory pattern of behavior was observed in fifty-seven fish whose tags were returned with sufficient data to determine migration. Of these 79 per cent were recaptured within five miles of the point of release 7 per cent wit?in ten miles, 5 per cent within fifteen miles, 4 per cent within twenty-five miles, and 2 per cent within forty miles of the point of release. 8. Distance migrated generally did not increase with the time the fish were free. 9. Short coastwise movements were made by four fish. Inshore movements were made by three fish during the winter, and offshore movements from a canal to the bay were made by two fish in the spring. 10. Age and growth was determined by counting and measuring the annuli of 590 otoliths. 11. Snook may reach the age of at least seven years. 12. Males Jive as long as the females, and were found in greater number in the fishery in all age groups except the VI and VII. In these age groups there were slightly more females. 13. Almost all snook are mature by their third year of life. 14. The commercial catch of Collier and Lee counties from September, 1956 to May, 1957 was composed principally of two-, three-, and fouryear- old snook. 15. The growth rate of the female snook was more rapid than the growth rate of the males in all age groups. Growth to the second year (both sexes) is rapid, then is fairly uniform to the fifth year, and slowly declines thereafter. 16. Field observations during June and early July indicated that snook spawn off the sandy beaches of passes and that the peak of spawning in 1956 was over after mid-July. 17. An egg count of a ripe 584 mm (23 inches) snook totaled 1,440,000. 18. The snook population of Florida is probably a small one fluctuating with changes in its ecology, but, being a relatively fast-growing early-maturing fish, it can probably maintain its abundance when conditions are normal.

Aspects of the Biology of the Common Snook, Centropomus undecimalis (Bloch) of Southwest Florida

Series