Fishing for the Facts

Zechariah Turk | Aransas Bay Ecosystem | TPWD Coastal Fisheries Division
Fishing for the Facts
Gill nets are much less selective than anglers for sampling adult and sub-adult populations.

Texas Parks and Wildlife Department’s mission statement is “To manage and conserve the natural and cultural resources of Texas and to provide hunting, fishing, and outdoor recreation opportunities for the use and enjoyment of present and future generations.” To achieve this goal, the Coastal Fisheries Division makes fisheries management decisions informed by a variety of survey methods. Some of the necessary data is collected directly from anglers and commercial fishers during boat ramp surveys, but to fully understand the state of our estuarine communities, we must also go out and collect samples from the wild to estimate species abundance from data that aren’t limited by angler habits and preferences. Gill nets are one of the most important and effective gears that fisheries biologists use to collect these data.

The TPWD gill net monitoring program has been a source of contention for decades. For some, the words “gill net” conjure thoughts that the Texas coastline is covered in miles of fishing nets, similar to times before commercial gill netting was banned in 1980. Gill nets are clearly an efficient and effective method to catch and quantify fish, which is ultimately the reason that commercial gill netting was banned several decades ago. Due to a number of misconceptions and misunderstandings, many anglers have voiced their concerns to our biologists about this program. Since the gill net gear can provide such important information about coastal resources, it is important to know exactly how TPWD uses this sampling gear, and more importantly, why it is still necessary. 

A gill net is a large monofilament net designed to entangle passing fishes. Each TPWD gill net consists of four 150 ft panels of varying mesh sizes (3” to 6” across). Nets are set perpendicular to the shoreline with the smallest mesh sizes on the shoreward side. Nets are set just before sunset, and retrieval begins as soon as possible after sunrise to reduce interference with anglers. Only 45 nets are used for sampling each spring and fall in each of the eight major bays along the Texas coast. Within a given bay, no more than five nets are set each week, and no more than three are set at a single time. It has often been thought that TPWD will set nets in fishing hot spots, however, TPWD staff do not select the gill net sampling sites. The location of where each net will be set is predetermined by a computer that randomly selects an area of shoreline habitat from a database of all areas that can be sampled within a bay; this random approach of choosing where a net is set ensures that the data collected are spatially unbiased. If only fishing hot spots were sampled by gill nets, this could inflate catch estimates and lead to the population appearing larger than it actually is.

Gill nets are ideal for sampling adult and sub-adult fish that are otherwise difficult to assess, because some species and age classes are more likely to avoid or escape other sampling gears used in TPWD’s Resource Monitoring Program; other techniques commonly used in freshwater fishery sampling (e.g. electrofishing) are simply not practical or possible in marine environments. Compared to data collected at angler surveys, gill nets also provide a less biased snapshot of catch. The nets are much less selective than anglers for targeting only a small subset of species, and the landings are not as constrained by size or bag limits. While there is some mortality associated with fish captured in nets, many don’t realize that the amount of fish impacted by TPWD gill nets is negligible when compared to those harvested by recreational fishing. For example, coastwide, TPWD catches an average of 6,768 spotted seatrout each year, many of which are released alive. Those landings in TPWD gill nets account for only 0.7 % of the 913,660 estimated trout harvested each year by recreational anglers in Texas [not counting those caught and released by anglers].

TPWD Biologists are also trained to properly handle fish to maximize survival of those landed in gill nets. Live fish are measured and released as quickly as possible, and a live basket is kept onboard the sampling vessel to allow captured fish to recuperate. Survival rates vary by species, and it is heavily determined by how much time has lapsed since capture and if environmental parameters, like dissolved oxygen and temperature, are in an optimal range. Fish that do succumb to the stress of being captured are certainly not wasted. TPWD collect additional data from these specimens to provide more in-depth information that is critical to managing the fishery. For example, reproductive structures can be evaluated to assess sex ratios, otoliths (the inner ear stones of fish) can be extracted to examine age and growth, and various tissues can be collected to conduct genetic and diet studies. Once all of the scientifically valuable information has been collected, any fish that do not survive and are deemed edible are donated to charitable organizations that feed the local community.

TPWD Coastal Fisheries has one of the largest and most continuous marine resource databases in the world. Our data continues to prove to be fundamental for successfully managing this great State’s marine resources. The data that TPWD collects by sampling with gill nets is one piece of the puzzle that is used in combination with data collected through angler surveys and other fisheries sampling gear (i.e., shoreline bag seines and trawls) to make informed resource management decisions. TPWD continues to explore new sampling methods and incorporates new gears into the monitoring program once it shows it can provide the same or better information than our current sampling methods. Ultimately, TPWD will continue best practices to achieve the goals outlined in its Mission Statement.

If you have any questions or concerns, feel free to contact your local Coastal Fisheries Field Office (https://tpwd.texas.gov/about/administration-divisions/coastal-fisheries/field-offices).
 
Premium content for TSF Insiders.

To continue reading, Login or become a Subscriber!