fish in hand

Expansion of Juvenile Snook Sampling in Tampa Bay, Charlotte Harbor and the Indian River Lagoon

by Brent Winner, Tim MacDonald and Dave Blewett

men and woman in water holding net
Photo: Chris Johnson (volunteer), Brittany Hall, Ryan Jones, and Brad Lenhart. FIM scientists gather the catch into the bag of the seine. The fish are then transferred to the boat where they are identified, counted, and measured for length.

Snook are one of Florida’s most popular sportfish. In 2013, the Stock Assessment group at the Florida Fish and Wildlife Conservation Commission’s (FWC) Fish and Wildlife Research Institute (FWRI) evaluated available juvenile snook data sources to determine the feasibility of incorporating age-1 juvenile snook information into the snook stock assessment. These data were found to be insufficient and FWRI’s Fisheries Independent Monitoring (FIM) program was tasked to develop a sampling program to improve estimates of abundance and size-at-age for age-1 snook.

In July of 2013, a “Snook Team” consisting of FIM staff from the Tampa Bay, Charlotte Harbor, and Indian River field labs was formed.  Team members looked at historical datasets to define the size range of age-1 snook, to examine temporal and spatial trends of age-1 snook, and to determine how mesh and gear size related to selectivity.  Preliminary gear testing and reconnaissance trips were conducted to establish gear specifications, sampling universes, and sampling design.  Methods were developed for site selection, gear deployment and retrieval, sample work-up and culling of specimens for age determination.  In July 2014, gear testing in Tampa Bay, Charlotte Harbor, and the Indian River Lagoon began with two sizes of center-bag seines (21.3-m with 3.2-mm mesh and 40-m seine with 25.4-mm mesh) being deployed by boat at each randomly selected site. A total of 1,872 seine hauls were conducted during the 12-month gear testing period, yielding 2,315 snook; of these, 1,285 were young-of-the-year (< 99 mm SL) and 714 were presumed age-1 (100-300 mm SL).

man's hands holding fish
Scientist measures a snook prior to release. Based upon its size this individual is approximately 1 year old.

To adequately assess potential habitats used by juvenile snook, the gear testing study design included habitats and geographic areas (i.e., backwater and tidal creek habitats; small seines sampling in the southern IRL) that had not been included in previous FIM program sampling.  This sampling also provided data on a wide variety of other estuarine fish and invertebrate species. In Tampa Bay 278,763 specimens were collected representing 108 taxa.  Charlotte Harbor collected 59,013 specimens (73 taxa) and Indian River Lagoon caught 183,225 specimens (162 taxa).

fish in net
Seine sample collected in the lower Manatee River by FIM scientists. Catches often include many species of fishes, crabs, and shrimp. Notice the young of the year snook in the lower center of the picture by the ruler.

The gear testing data were analyzed to determine habitat selectivity, spatial and temporal distributions, and catch rates of snook by gear.  The 21.3-m seine provided the most consistent assessment of all sizes of juvenile snook as well as other fishes and macroinvertebrates in the habitats where juvenile snook were prevalent.  Based on this information, the FIM program added a standardized sampling design for juvenile snook using the 21.3-m seine into its monitoring program in January 2016.  This sampling design included several rivers and many tidal creeks previously not sampled with this gear in Tampa Bay, Charlotte Harbor, and the Indian River Lagoon.  These data have already been used in the 2016 snook stock assessment.

On January 13, 2016 the most recent snook stock assessment and some ongoing snook research studies being conducted at FWRI were presented at the FWC hosted Snook VI Symposium in Orlando, Fl.  The objective of this meeting was to initiate a discussion and process that could result in new management goals for snook.  The symposium was attended by several hundred fishermen, industry stakeholders, and members of the academic and scientific community from throughout the state.  Following updates on research and the status of the stocks, the public was offered an opportunity to share their opinions and concerns on the status of snook in Florida.  One of the top concerns of the attending stakeholders was the lack of information on juvenile snook habitats. They were also concerned about and the vulnerability of juvenile habitat to anthropogenic alteration.  Many of these habitats are directly addressed by the new juvenile snook sampling design initiated by the FIM program.  This new data stream will continue to be valuable for the management of snook, and many other species, in future years.

For more information on the Snook VI Symposium, visit the FWC website  (MyFWC.com/Snook2016).