Gary C. Matlock

A Method for Directly Estimating the Tag-Reporting Rate of Anglers

Abstract Tag-reporting rates for marine recreational boat anglers were estimated directly by surreptitiously implanting, during routine creel surveys, fish tags into fish that had already been caught during October 1976-September 1978. Twenty-nine percent (177) of the 600 implanted tags were returned. Ninety-five percent of all tags returned were received within 100 days after they had been implanted. Significant differences (P ≤ 0.05) were found among reporting rates by anglers from different fishing areas and for different species of fish. No significant differences were found for reporting rates by anglers among seasons or years. These results indicate that use of reward tags in other studies has not fully corrected for nonreporting of recovered tags and, consequently, fishing mortality estimates based on them have been underestimates. The vast majority of anglers (96%) correctly identified their fish to genus and they reported fish lengths that were within ±76 mm (SD) of those determined by agency sta...

Importance of Fish Consumption to Sport Fishermen

Abstract Retention and consumption of fish by sport fishermen are generally reported in the scientific literature to be less important than the recreational experience. On this basis, the Texas Parks and Wildlife Commission prohibited for 120 days the retention of red drum (Sciaenops ocellatus) and spotted seatrout (Cynoscion nebulosus) in a small bay after a massive coastwide fish kill in 1984. Simultaneously, the bag, possession, and size limits for these species were made more restrictive in all other Texas bays on the Gulf of Mexico. An attempt to adopt the rule prohibiting retention on a permanent basis was adamantly opposed by fishermen for the affected bay. This response was unexpected. Either the generalization that keeping fish is not very important is incorrect, or the fishermens reaction is a localized phenomenon and within the expected variation of the published generalizations. This study examines five possible explanations for the generalization being incorrect. Inadequacies in data gatheri...

A Bioeconomic Analysis of the Texas Shrimp Fishery and Its Optimal Management

Overfishing in the Texas shrimp fishing industry by time period and fishing area is investigated. An optimal harvesting pattern is determined using a multiperiod mathematical programming model where prices, fishing effort, catch, and resource dynamics are treated endogenously. These results are then compared with actual effort. The comparison indicates substantial excess effort in spring and early summer, especially in the bays and shallow offshore areas. The peak fishing season also occurs later in the fall in optimal harvest pattern than in practice. The results indicate both producers and consumers gain from reduced fishing effort because of improved size composition of the harvest.

Nonreporting of Recaptured Tagged Fish by Saltwater Recreational Boat Anglers in Texas

Abstract Internal abdominal tags were surreptitiously implanted in 301 fish caught by saltwater recreational boat anglers during creel survey interviews. Eighty-four of 301 anglers subsequently reported their tagged fish, yielding a reporting rate of 28%. Of 154 anglers later contacted, 73 had found the tag and only one knew that the tag had been secretly implanted during the interview. Five anglers suspected that the tag had been implanted. Failure to report tags was most often a result of failure to find the tag. This technique appears suitable for estimating the nonreporting of recaptured tagged fish, at least for week-end boat anglers.

Management Briefs: Short-Term Hooking Mortalities of Red Drums and Spotted Seatrout Caught on Single-Barb and Treble Hooks

Abstract Short-term (3-d) hooking mortalities of red drums Sciaenops ocellatus and spotted seatrout Cynoscion nehulosus caught with single-barb hooks were compared with hooking mortalities for those caught with treble hooks in Texas bays in the summers of 1989 and 1990. Natural baits (primarily penaeid shrimp) and artificial baits (spoons, worms, and fish-shaped lures) were used with both hook types. Overall mortality of 121 red drums was 4.1 % at the end of 3 d after capture, and there were no significant (P = 0.67) red drum mortality differences between hook types or bait types. Mortality of 124 spotted seatrout was 7.3% by 3 d after capture, and no significant (P = 0.27) differences between hook types or bait types were found. Restricting anglers to one hook type (either single-barb or treble hooks) would not reduce unintended fishing mortality for either species.

Burrow utilization by yellowedge grouper, Epinephelus flavolimbatus, in the northwestern Gulf of Mexico

SynopsisSubmersible dives were made on a site in the Gulf of Mexico 160 km southeast of Galveston, Texas in September 1984. Both yellowedge, Epinephelus flavolimbatus, and snowy grouper, E. niveatus, were observed utilizing shelter around rock ridge habitats. The yellowedge grouper also sought shelter within three types of burrows cut into soft sediment. Many of these burrows were significant excavations consisting of large trenches 7–8 m long, 2–3 m wide, and 1–1.5 m deep. Burrows were found in depths from 265 to 290 m. Tilefish, Lopholatilus chamaeleonticeps, also occur at this site, usually inhabiting the characteristic vertical burrows already described for this species. In four daytime submersible transects covering a linear distance of over 13000 m, we observed a total of 66 yellowedge groupers. Twenty-five were in burrows, 39 among rocks, and two over open bottom. It is suggested that this species may have an advantage over congeners that utilize only rocky habitat for cover. It may also compete for shelter with tilefish at depths where the two species overlap.

Temporal Stability of Nuclear Gene (Allozyme) and Mitochondrial DNA Genotypes among Red Drums from the Gulf of Mexico

Abstract Allelic variation in nine polymorphic nuclear genes and restriction-site variation in mitochondrial DNA (mtDNA) were assayed among 194 adult red drums Sciaenops ocellatus from the northern Gulf of Mexico, Data were combined with those of previous studies in order to examine patterns of temporal genetic variation among four year-classes (1984–1987) and individuals spawned prior to 1984, Tests of heterogeneity among year-classes in both nuclear gene allele frequencies and mtDNA haplotype frequencies were nonsignificant, and estimated fixation (F ST) values were 0.009 (nuclear genes) and 0.002 (mtDNA). Estimates of Neis unbiased genetic distance (nuclear genes) and nucleotide sequence divergence (mtDNA) among year-classes also indicated the absence of temporal genetic differentiation, Estimates of average heterozygosity (nuclear genes) and nucleon and nucleotide sequence diversities (mtDNA) indicated that levels of genome-wide variation within and among year-classes of red drum are equivalent to (o...

Zooplankton Abundance in Unstocked Mariculture Ponds at Three Salinities

Abstract Zooplankton abundance in unstocked saltwater fish culture ponds was studied over 4 weeks in southern Texas. Paired 0.2-hectare ponds were filled with bay and well water to yield salinities of 10, 15, and 20‰ and were fertilized with 568 kg cottonseed meal per hectare. Dominant zooplankton groups were compared to determine which salinity produced the best forage base for culture of euryhaline marine fish. Peak total zooplankton densities occurred at day 9 in 10‰ salinity ponds, and day 23 in the 15 and 20‰ salinity ponds. Further, peak total zooplankton densities were approximately five times greater in the 10‰ salinity ponds than in the 15 and 20‰ salinity ponds. Acartia tonsa densities were unaffected by the salinities tested. Oithona sp. densities were significantly greater at 15‰. Densities of mixed rotifers, copepod nauplii, and polychaete larvae were significantly greater at 10‰. Accordingly, pond salinities of 10‰ appeared to provide the best zooplankton forage base for culture of euryhalin...

Evaluation of the Accuracy and Precision of Volunteered Size Data from Tagged Red Drum Returns

Abstract The accuracy and precision of total lengths and weights from recaptured tagged red drum (Sciaenops ocellatus) reported by Texas Parks and Wildlife Department (TPWD) biologists, anglers, and commercial fishermen were compared. No differences were found in the total length-weight regressions of data reported by sport and commercial fishermen, but there were significant differences found between data reported by fishermen and data collected by TPWD biologists (F, = 6.312; P < 0.05). Fish lengths reported by fishermen were not biased but they were more variable than lengths reported by TPWD due to rounding to the nearest whole or partial English unit. Weights reported by fishermen were more variable than weights reported by TPWD biologists. A significant difference between regression coefficients was found and a comparison of confidence limits of the regression lines showed that fishermen overestimated the weight of small fish; therefore, growth estimates calculated from red drum weights provided by ...

Sampling nearshore estuarine fishes with rotenone

Abstract Sampling with rotenone is an effective method for providing abundance estimates of estuarine fishes at nearshore locations. However, the determination of recovery rates for individual species is critical for estimating abundance by this technique. Recovery rates in this study varied greatly among species, but did not vary among station types (cove or shoreline) or sample years (1976 or 1977). Tagged fishes, used to establish recovery rates, did not change in weight due to the sampling procedures from time of introduction to time of collection. Total adjusted abundance estimates ranged from 157 to 18,300 fishes/hectare and from 36 to 4,080 kg/hectare for fishes greater than 124 mm in Texas estuaries. Mean number and weight of fishes per hectare were generally greater at cove stations than at shoreline stations. Timing for the application of rote-none in estuaries is important to avoid extensive bird predation.