| 29 April 2009
From 1997 to 2007, Nate released over 50,000 tagged, hatchery-raised snook in several controlled release experiments.
The population of mature common snook in both the Atlantic and Gulf coasts has been studied and measured in a variety of methods. However, relatively little is known about the life of juvenile snook. Dr.Nate Brennan has made this his pursuit over the last 10 years. Nate is a scientist in the Center for Fisheries Enhancement at Mote Marine Laboratory. He has been involved in stock-enhancement research for 17 years.
Nate has focused his work on the influence of habitat on the overall health of juvenile common snook populations. He uses hatchery raised snook as his sample group to measure survival, dispersal and recruitment to the native snook population in several creeks and barrier-island passes. His pre-release work went something like this: habitats were studied to determine salinity, oxygen content, slope, composition of sediment and other features.
Hatchery raised snook were studied to see how they survived once they joined native snook populations.
Between 1998 and 2005 Nate collected 18,344 Snook (some hatchery, mostly wild) from beaches, passes, barrier island habitats and release sites. Hatchery raised snook were identified by the presence of tiny coded wire tags.
Nate was looking at how various release habitats affect growth, survival rate and recruitment into wild snook stocks.
Of Snook released in 1998 and 1999 at upstream and midstream creek locations and along island shorelines, 174 hatchery snook were recaptured after being at sea for over 1 year. Most long term recaptures were found at their release sites but 42 were considered dispersed and were captured along beaches, passes and barrier island habitats.
The largest recaptured hatchery snook so far has been 34 inches total length and weighed 12.1 pounds (she made it through the slot gauntlet!) The longest time at liberty was 6.57 years.
Young snook seek refuge in areas where they can avoid predators yet sneak an occasional meal. Due to never ending coastal development, such refuges for growing snook are at a premium.
In Sarasota, North Creek consistently produced more juveniles per unit area than other habitat studies in Sarasota Bay, and thus represents a primary nursery habitat for snook in Sarasota. This creek is the least developed of the creeks studied and has many characteristics correlated with high juvenile survival (high organic content in the sediment, low salinity, hypoxic conditions in summer), as well as shallow depths and abundance of mangrove shoreline.
Why this is important to snook enthusiasts
In Nate's study, tidal creeks with the highest growth rates had the lowest survival; these habitats were also highly altered through seawalls, canalization and creeks routinely dredged. In other words, the fish were bigger in developed areas, but not as many lived to maturity.
Base level research like this is desperately needed to quantify the ongoing battle to identify and save “essential” fish habitat.
With qualified, data-driven researchers working on quantifiable data such as this, we will be better armed when we take the fight to our neighbors and community leaders throughout Florida. Thanks, Nate!
