Nekton Monitoring

The Approach

In partnership with NOAA, the Institute is currently supporting this effort by conducting targeted data collection and analysis to establish reference ranges and restoration targets for focal nekton associated with Louisiana’s estuarine and coastal habitats of Barataria and Terrebonne Basins. This effort is composed of three umbrella tasks:

1. Compile and analyze existing fish and invertebrate data for coastal Louisiana and development of fixed-area sampling protocol.
2. Collect new data through field work to characterize fish and invertebrate densities within coastal Louisiana restored and reference marshes using fixed-area sampling approaches.
3. Analyze Task 2 coastal Louisiana fixed-area fish and invertebrate density dataset to identify restoration targets and reference ranges for focal nekton species and/or guilds.

This project is implemented in close collaboration with NOAA’s Lower Trophic Level project (Diver Project #269) to align water quality and lower trophic level standing stock data with higher order nekton and fish species in the Barataria Basin.

Project Successes to Date

Task 1 Compile and analyze existing fish and invertebrate data for coastal Louisiana and development of fixed-area sampling protocol

Between 2023 and 2024, the Institute, alongside project partners at NOAA, the U.S. Geological Survey (USGS), the Louisiana Department and Wildlife and Fisheries (LDWF), Dynamic Solutions LLC, and Louisiana State University (LSU), collaboratively investigated whether potential effects of marsh habitat restoration in Barataria and Terrebonne Basins could be detected through analysis of existing long-term fisheries-independent monitoring program (FIMP) data. This effort identified focal species for analysis and developed a series of generalized additive models (GAMs) to investigate potential effects of restoration on relative abundance and diversity while accounting for sources of intra- and interannual natural variability (e.g., salinity, seasonality) and habitat characteristics (e.g., landscape configuration) which may affect the distribution and abundance of marsh-associated nekton.

Figure 1. Example of model outputs of the two restoration effect parameters included in the generalized additive models back-transformed to relate effects on catch-per-unit-effort (CPUE).

Task 1 culminated in identification of statistically significant potential effects of restoration (measured as time since restoration and average distance away from a completed restoration project), but further analyses are required to better understand the ecological significance of these effects and better understand the potential confounding/interacting variables. A peer-reviewed journal publication of this work is forthcoming. Future analyses will be conducted to establish FIMP-related reference ranges and restoration targets, as appropriate.

Finally, the project team worked closely with NOAA’s Southeast Fisheries Science Center (SEFSC) to develop a field-based monitoring plan necessary to implement fixed-area nekton monitoring techniques (also termed enclosure sampling) as part of Task 2 of the project (discussed below).

Project-Related Outputs:

• Kiskaddon et al., Effects of marsh habitat restoration and fragmentation on nekton abundances in coastal Louisiana – peer-reviewed journal article under review

• Marshall et al., 2024 Nekton Fixed-Area Gear Type Literature Review and Existing Data Summary for Barataria and Terrebonne Basins – tech memo

• Kiskaddon et al., 2023 Literature Review of Recent Analyses on Outputs from Louisiana Fisheries Independent Monitoring Program (FIMP) Data – tech memo

• Kiskaddon et al., 2024 Fixed-Area Monitoring Plan & Protocols for Barataria and Terrebonne Basins – report

Task 2 Collect new data through field work to characterize fish and invertebrate densities within coastal Louisiana restored and reference marshes using fixed-area sampling approaches

In partnership with SEFSC, the Institute will implement the field-based monitoring program outlined in Task 1 in Terrebonne and Barataria Basins. The following data types are expected to be collected over a period of three years 2025-2028:

• Nekton abundance, community composition, diversity, and density

• Environmental parameters such as water temperature, salinity, pH, dissolved oxygen, and water depth.

• Habitat characteristics such as marsh vegetation density and community composition and sediment quality.

Drop sampling, a type of fixed-area sampling method, is employed to collect nekton species in marsh edge or open water habitat. The drop sampler consists of a large fiberglass cylinder, resembling a tube, suspended from the bow of a specialized vessel. As the vessel approaches the marsh, the drop sampler is released and nekton captured within the enclosed space. Organisms are removed by hand using dip nets, and water is suctioned out to ensure all organisms are collected.

Project-Related Outputs:

• Ongoing implantation of nekton monitoring across Barataria and Terrebonne Basins in collaboration with the NOAA Southeast Fisheries Science Center (SEFSC). Data collection expected to occur seasonally between 2025 and 2028 with data made publically available via NOAA’s DIVER portal.

Activity Photos:

Figure 2. TWI Nekton field team, Erin Kiskaddon (left) and Maricel Burgos (right), collecting organisms from the drop sampler in saline marsh edge habitat in Barataria Basin.

Figure 3. TWI Nekton field team, Emelia Marshall (left) and Maricel Burgos (right), deploying the drop sampler in freshwater marsh edge habitat in Barataria Basin.

Figure 4 TWI Nekton field team, Maricel Burgos (left) and Emelia Marshall (right), collected water quality data from open water in Barataria Basin.

Figure 5. Nekton species collected from the drop sampler: (left) Goby, (middle) juvenile Croaker and Pinfish, (right) pipefish