Discard Mortality of Red Snapper Released with Descender Devices in the U.S. South Atlantic

Abstract.—Red snapper Lutjanus campechanus were sampled from commercial landings from the Gulf of Mexico (GOM) off Louisiana from October 2001 to May 2004. Fork length (FL), eviscerated weight, otoliths (both sagittae), and sex determinations were taken from 2,900 specimens; FL was subsequently converted to total length (TL) with the equation TL = 1.073 (FL) + 3.56. Red snapper ages (N = 2,867) estimated from counts of opaque annuli in otoliths ranged from 1 to 14 years; however, the vast majority (97.7%) of these were ages 2 to 6 years and the modal age was 3 years. Total lengths among 2,897 specimens ranged from 278 to 940 mm, modal TL was 400 mm, and 98% of all specimens were less than 600 mm TL. We also investigated the fate of red snapper regulatory discards (individuals <381 mm [15 in] TL) during 16 trips on working commercial vessels; over two-thirds of 4,839 red snapper assigned among four discard fate categories (ranging from alive and vigorous to dead) were returned to the water either in moribund or dead condition. Among 399 potential discards retained for age and length analyses, 86% were between 12 and 15 in (305–381 mm) TL and 85% were 2 years of age. The minimum size regulation appears to do little to protect juvenile red snapper from commercial fishing mortality. Heavy red snapper mortality, which begins as bycatch mortality in shrimp trawls, continues as discard mortality at sub-legal lengths when they first recruit to the offshore fishing grounds, and persists as harvest mortality among the youngest legal year- and size-classes. If the minimum size limit is intended to provide a respite from such mortality, a reconsideration of the utility of the minimum length regulation in the commercial harvest of red snapper may be warranted.

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico ◽

10.47886/9781888569971.ch1 ◽

2007 ◽

Keyword(s):

Gulf Of Mexico ◽

Red Snapper ◽

The U.S

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico ◽

10.47886/9781888569971.ch3 ◽

2007 ◽

Keyword(s):

Gulf Of Mexico ◽

Red Snapper ◽

Lutjanus Campechanus ◽

Nursery Areas ◽

Side Scan Sonar ◽

Bathymetric Data ◽

Habitat Effect ◽

Inner Continental Shelf ◽

The U.S ◽

Trawl Surveys

Abstract.—Trawl surveys were conducted to measure patterns of habitat use by newly settled red snapper Lutjanus campechanus at three natural banks on the inner continental shelf of Texas. Digital side-scan sonar and multibeam bathymetric data were used to define inshore (mud), ridge (shell), and offshore (mud) habitats for Freeport Rocks, Heald Bank, and Sabine Bank. Otter trawls were conducted July through September in 2003 (Heald Bank, Sabine Bank) and in 2004 (Freeport Rocks) during the settlement period of red snapper. Freeport Rocks had markedly higher densities of red snapper (91 ha⁻1) in 2004 than Heald Bank (6 ha⁻1) or Sabine Bank (<1 ha⁻1) in 2003. A significant habitat effect was observed at Heald Bank and densities were higher at offshore mud habitats; no habitat effect was detected for Freeport Rocks or Sabine Bank. Growth rates varied from 0.86 mm‧d⁻1 at Sabine Bank up to 1.12 mm‧d⁻1 at Freeport Rocks, and rates were higher on inshore and offshore mud than ridge habitats. Otolith-based estimates of age indicated that settlers were first detected at 22–28 d and the majority of individuals were 30–60 d. Hatch dates peaked from early June to early July in both 2003 and 2004. Results from this study indicate that both shell and inshore and offshore mud habitats associated with these natural banks serve as settlement habitat of red snapper, and all three habitats have the potential to function as nursery areas of this species.

Inferences regarding initiation of oceanic crust formation from the U.S. East Coast margin and conjugate South Atlantic margins

Atlantic Rifts and Continental Margins - Geophysical Monograph Series ◽

10.1029/gm115p0211 ◽

2000 ◽

pp. 211-233 ◽

Cited By ~ 31

Author(s):

Manik Talwani ◽

Vitor Abreu

Keyword(s):

Oceanic Crust ◽

East Coast ◽

South Atlantic ◽

Crust Formation ◽

The U.S

Air-sea CO2fluxes on the U.S. South Atlantic Bight: Spatial and seasonal variability

Journal of Geophysical Research Atmospheres ◽

10.1029/2007jc004366 ◽

2008 ◽

Vol 113 (C7) ◽

Cited By ~ 88

Author(s):

Li-Qing Jiang ◽

Wei-Jun Cai ◽

Rik Wanninkhof ◽

Yongchen Wang ◽

Heike Lüger

Keyword(s):

Seasonal Variability ◽

South Atlantic ◽

South Atlantic Bight ◽

The U.S

Benthic community structure on the U.S. South Atlantic slope off the Carolinas: Spatial heterogeneity in a current-dominated system

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/0967-0645(94)90051-5 ◽

1994 ◽

Vol 41 (4-6) ◽

pp. 835-874 ◽

Cited By ~ 51

Author(s):

James A. Blake ◽

J. Frederick Grassle

Keyword(s):

Community Structure ◽

Spatial Heterogeneity ◽

Benthic Community ◽

South Atlantic ◽

Benthic Community Structure ◽

A Current ◽

The U.S

Modeling Discards in Stock Assessments: Red Grouper Epinephelus morio in the U.S. Gulf of Mexico

Fishes ◽

10.3390/fishes7010007 ◽

2021 ◽

Vol 7 (1) ◽

pp. 7

Author(s):

Kyle W. Shertzer ◽

Erik H. Williams ◽

Skyler R. Sagarese

Keyword(s):

Gulf Of Mexico ◽

Stock Assessment ◽

Time Varying ◽

Discard Mortality ◽

Stock Assessments ◽

Epinephelus Morio ◽

Red Grouper ◽

Management Advice ◽

The U.S

To be as accurate as possible, stock assessments should account for discard mortality in fisheries if it occurs. Three common approaches to modeling discards in assessments are to lump dead discards with landings, treat dead discards as their own fleet, or link them conversely with landings through use of a retention function. The first approach (lumping) implicitly assumes that the selectivity of landings applies also to discards. In many cases, that assumption is false, for example, if discards comprise smaller fish than do landings. The latter two approaches avoid the assumption by modeling discards explicitly with their own selectivity pattern. Here, we examine these approaches to modeling discards. Using a simulation study, we demonstrate that the two approaches to modeling discards explicitly can provide identical results under both static and time-varying conditions. Then, using a stock assessment case study of red grouper Epinephelus morio in the U.S. Gulf of Mexico, we demonstrate that in practice the approaches to modeling discards can provide different outcomes, with implications for the resultant management advice. We conclude by comparing and contrasting the different approaches, calling for more research to elucidate which approach is most suitable under various sources of error typically encountered in discard data.

Application of three-dimensional acoustic telemetry to assess the effects of rapid recompression on reef fish discard mortality

ICES Journal of Marine Science ◽

10.1093/icesjms/fsz202 ◽

2019 ◽

Vol 77 (1) ◽

pp. 83-96 ◽

Cited By ~ 2

Author(s):

Erin Collings Bohaboy ◽

Tristan L Guttridge ◽

Neil Hammerschlag ◽

Maurits P M Van Zinnicq Bergmann ◽

William F Patterson

Keyword(s):

Acoustic Telemetry ◽

Proportional Hazards ◽

Three Dimensional ◽

Reef Fishes ◽

Cox Proportional Hazards ◽

Red Snapper ◽

Large Area ◽

Discard Mortality ◽

Study Sites ◽

Gray Triggerfish

Abstract Geopositioning underwater acoustic telemetry was used to test whether rapid recompression with weighted return-to-depth (descender) devices reduced discard mortality of red snapper (n = 141) and gray triggerfish (n = 26) captured and released at 30–60 m depths at two 15 km2 study sites in the northern Gulf of Mexico. Cox proportional hazards modelling indicated red snapper released with descender devices had significantly lower discard mortality within the first 2 d (95% CI = 18.8–41.8% for descender-released vs. 44.0–72.4% for surface-released, unvented fish), while there was no significant effect of descender devices on discard mortality of gray triggerfish. Predation by large pelagic predators was estimated to account 83% of red snapper and 100% of gray triggerfish discard mortality. Discard mortality due to predation has likely been overlooked in previous mark-recapture, laboratory, and enclosure studies, suggesting cryptic population losses due to predation on discards may be underestimated for red snapper and gray triggerfish. Large-area three-dimensional positioning acoustic telemetry arrays combined with collaboration and data sharing among acoustic telemetry researchers have the potential to advance our knowledge of the processes affecting discard mortality in reef fishes and other taxa.

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico

Red Snapper: Ecology and Fisheries in the U.S. Gulf of Mexico ◽

10.47886/9781888569971.ch2 ◽

2007 ◽

Keyword(s):

Time Series ◽

Gulf Of Mexico ◽

Mississippi River ◽

Red Snapper ◽

Survey Area ◽

Lutjanus Campechanus ◽

Data Set ◽

Stock Size ◽

Central Texas ◽

The U.S

Abstract.—Eleven taxa of snappers were found among the 20,301 snapper larvae examined from over 14,000 bongo and neuston samples collected during SEAMAP surveys, 1982 to 2003. During that time series, a total of 639 red snapper Lutjanus campechanus larvae were identified in bongo samples and 1053 larvae in neuston samples. Red snapper larvae first appeared in May and were present as late as November. Months of highest occurrence and abundance were July and September when larvae were taken in 12.7% and 11.0% of bongo samples, and in 7.6% and 8.4% of neuston samples. Mean abundance in those months was 1.18 and 0.82 larvae under 10 m2 of sea surface for bongo samples and 0.36 larvae per 10 min for neuston samples. By November, percent occurrence was less than or equal to 0.2% and mean abundance was less than 0.01 larvae in samples from either gear. Larvae identifiable as red snapper ranged in body length from 2.4 to 19.2 mm (mean = 5.12, median = 4.60) in bongo net samples; and 2.7–24.0 mm (mean = 4.37, median = 4.00) in neuston net samples. Over 95% of larvae in bongo samples were less than or equal to 8.3 mm and in neuston samples were less than or equal to 5.6 mm. Larvae were captured throughout the survey area but were consistently observed in greatest abundance at stations on the mid-continental shelf west of the Mississippi River, especially off western Louisiana and central Texas. This time series of observations is the data set from which annual estimates of larval red snapper abundance were derived for use as a fishery independent index of adult stock size.