CATCH-AND-RELEASE MORTALITY OF SPOTTED SEATROUT IN TEXAS

Coastal Conservation Association (CCA-Texas) has graciously funded the Fisheries Ecology lab to conduct two studies (Phase I and Phase II) examining catch and release mortality of spotted seatrout in Texas . Below are summaries of these studies.  Please see the publications page for details resulting from these studies. 

Catch and release is becoming more common as a management tool in marine recreational fisheries.  Clearly, a critical factor in determining different management scenarios using this strategy is post-capture survival.  The purpose of these studies was to investigate the mortality associated with catch and release in the spotted seatrout Cynoscion nebulosus fishery in south Texas . 

 Phase I Summary: 

  This study investigated the mortality for hook-and-line-captured spotted seatrout as a function of bait type, hook type, angler skill level, and fish size.  We captured 448 spotted seatrout ranging from 250-760 mm total length (TL) using a variety of angling techniques and assessed mortality using replicate field enclosures.  A relatively low overall short-term mortality for all treatments was observed with the majority of fish surviving.  The exception was with angler skill level, where novices had a significantly higher mortality rate than skilled anglers; however, mortality averaged only 18% even with inexperienced anglers.  To evaluate long-term mortality spotted seatrout were held in a laboratory facility for 30 d.  Spotted seatrout showed no signs of long-term mortality. In an attempt to increase the abundance of "trophy" spotted seatrout, new slot limit regulations in Texas allow only one fish per person per day over 635 mm.  We targeted larger (635-736 mm TL) fish to assess the mortality associated with this size group.  Regression analysis showed no size-related mortality.  The location of hook-related injuries may be the most important factor in determining catch-and-release mortality. Anatomical hooking location was not a factor in the analyses but treated as a component of experimental treatment level; however we observed that mortality was typically associated with hooking location rather than angling method or bait type.  These data suggest that management options involving the release of spotted seatrout, including release of fish > 635 mm TL (25 inches), are viable management tools.

Figure 2.  Mean percent catch-and-release mortality (± SE) of spotted seatrout captured using different bait types (soft plastic, live shrimp, and surface topwater plugs).  The p-value is from ANOVA, and N = 10 replicates for each treatment. 

Figure 3.  Mean percent catch-and-release mortality (± SE) of spotted seatrout captured using different hook types (offset shank Kahle, straight shank “j-shaped,” and treble).  The p-value is from ANOVA, and number at the base of the bar is the number of replicates for each treatment. 

Figure 4.  Relationship between fish size (TL mm) and percent catch-and-release mortality of spotted seatrout.  The p-value is from simple linear regression.  Spotted seatrout were assigned to 15 different size cohorts from 388 total fish.  At least five fish are represented in each cohort.

 Phase II Summary: 

  The purpose of this study was to estimate catch-and-release mortality associated with hook-and-line captured spotted seatrout by recreational anglers as a function of anatomical hooking location, season, and competitive sportfishing tournaments that have continued to increase in popularity over the last thirty years.  Additionally, a tagging study was conducted to assess post-tournament movement patterns of spotted seatrout.  From July 2004 to June 2005, a total of 479 spotted seatrout ranging from 220-555 mm total length (TL) were captured by hook-and-line in Aransas and Corpus Christi Bays and maintained in replicated 3.5-m³ field enclosures for 72 h.  Hooking location was assigned to four body regions: mouth, gills, esophagus, and external.  Overall mortality for the experimental study was 19%.  Study results suggest anatomical hooking location is a major factor influencing mortality; however, under normal fishing practices only approximately 12% of fish are hooked in locations that routinely caused mortality.  Fish hooked in the esophagus and gills had mortality rates of 95 and 75%, respectively, whereas fish hooked in the mouth and external had mortality rates of 10 and 8%, respectively.  Mortality was assessed from ten live-release fishing tournaments held from February 2004 – April 2006.  Combined overall mean percent mortality was 22.9% with combined initial and delayed mean percent mortality rates of 10.4 and 14.1%, respectively.  Delayed long-term (14 d) mortality of tournament caught spotted seatrout was 1.9%.  From July 2004 to June 2005, a total of 364 spotted seatrout ranging from 220 – 539 mm total length (TL) were captured by hook-and-line in Aransas and Corpus Christi Bays and maintained in replicated 3.5-m³ field enclosures for 72 h.  Overall mortality for the seasonal study was 6%.  A significant relationship was found between season and catch-and-release mortality of spotted seatrout with higher mortality rates in spring and summer months than fall and winter.  Three hundred fifty-one spotted seatrout were tagged with eight recaptures, tag recovery rate 2.3%.  Days at-large and distance traveled by recaptured fish were 7 – 63 d and 3 – 48 km, respectively.  Results from this study suggest spotted seatrout mortality during live-release tournaments is slightly higher than mortality observed under normal catch-and-release fishing practices and post-tournament delayed mortality is very low.  Results from this study suggest current catch-and-release management regulations for spotted seatrout are a viable management strategy.  These data also suggest tournament organizers should avoid holding events during late spring and summer when seasonal mortalities are the highest and consider multiple post-tournament release sites to disperse fish over a larger area.

Table 1.  Overall percent catch and mortality of spotted seatrout at designated anatomical hooking location.  The number of spotted seatrout caught on hook-and-line and released after 72-h observation period (total fish captured = 479; total fish released = 387; combined mortality rate = 19%).

Table 2.  Tag recovery data of spotted seatrout tagged from five live-release tournament events.  Days at-large were calculated from the release date to the recapture date.  Distance traveled was calculated from the release site to recapture site.

Figure 5.  Overall mean percent mortality (±SE) of spotted seatrout recorded at ten live-release fishing tournaments held from February 2004 – April 2006. Tournaments are designated by bay system (ABS = Aransas, GBS = Galveston , MBS = Matagorda, and ULM = Upper Laguna Madre), month (Feb, Mar, Apr, May, and Jun) and year (2004, 2005, and 2006) each event was held.

Figure 6.  Combined mean percent mortality (±SE) of spotted seatrout recorded during each observation period at ten live-release fishing tournaments held from February 2004 – April 2006.  Number of fish during each observation period indicated at base of bar.  Initial = percentage of dead fish from overall number of fish brought to weigh-in.  Delayed = percentage of fish that died in tournament holding tanks from original number of live fish placed in tanks.  Overall = percentage of all dead fish, initial and delayed, from overall number of fish brought to weigh-in.

Figure 7.  Monthly mean percent mortality (± SE) of hook-and-line caught spotted seatrout.  Number of replicates per month are indicated at base of bar.