FWRI Tackles Snook Migrations

Written by Ron Taylor | 06 January 2010

Ron Taylor breaks down the latest chunk of data on snook migrations throughout the year in the Charlotte Harbor Estuary.

Snook move to the rivers to escape the cold, right? Well, maybe not!

Snook are euryhaline and use the entire estuarine system- from far upriver seaward to the lower estuary and beyond.

The accepted paradigm that cold water temperatures cause snook to move to rivers in the wintertime may be true, however further study is needed to explain seasonal movement and abundance in their overall habitat.

This study reports seasonal sizes and abundance of snook from Charlotte harbor and its 3 main rivers.

Materials and Methods

• Snook were sampled in the 3 rivers every 3 months (seasonally- winter, spring, summer, and fall) using both random and fixed stations during 2004 through 2006.
• Transects consisted of 10 minutes of electro-fishing (pedal down, i.e., current applied to water).
• Snook were measured, stomachs lavaged, and released.
• The estuary was sampled monthly using a 600’ bag seine at random stations from 1997 up to now.
• Sizes and abundances were compared and tested statistically.

Shock boat used to collect snook for study

RIVERS

About 1,100 snook, that ranged from 4 inches to 43.5 inches, were captured in the 3 rivers

Abundances at fixed and random sites were the same during fall, spring, and summer; however, they were more abundant at fixed sites during the winter (the higher winter abundance in fixed sites suggests that biologists know where to find the most snook).

Common snook were most abundant in the Peace River, then the Myakka, and then the Caloosahatchee. This is somewhat surprising since the Myakka is the most pristine. However, the Peace is over 100 miles long and offers many diverse habitats that drain more watersheds, which in turn probably provide more food and primary production.

In all years, river snook were significantly more abundant in the fall. Abundances were greater in the winter than in the spring or summer.

Snook warming in shallow waters of the Peace River

ESTUARIES

About 7,700 snook were captured in the estuary with the seine that measured between 5.5” – 45.5”

Abundance was higher in the summer and lower in the winter.

The sizes of the snook were the same in each season.

Seasonal temperatures were the same in the river as in the estuary.

Ron Taylor, FWRI Snook Researcher, is hot on the trail of Snook's Secrets

Conclusion

Abundance of common snook in rivers was highest in the fall and winter and in the estuary during the spring and summer. Overall, they were most abundant in the rivers in the fall.

Sizes of common snook were not different by season in either the river or the estuary.

Snook do migrate from the estuary to the rivers during the fall and winter but it is not temperature driven. More snook move into the rivers during the fall prior to any cold front on the west coast of Florida.

The reason for this movement requires more study. Is it related to the end of the reproductive season, to food, to avoidance of predators while their metabolism is slower, or is it an innate characteristic of their life history and we may never find out? The answer is not clear yet, BUT I WILL LOOK!