Temporal progressions of Gulf red snapper stock biomass (million tons) and spawning stock biomass (SSB) from the 1880’s to 2015.

<p>Landings are indicated east and west of the Mississippi River. Figure obtained from SEDAR 31 Assessment Update [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172360#pone.0172360.ref016" target="_blank">16</a>].</p

Histological image of the ‘immature’ reproductive phase in the red snapper ovary.

<p>Primary growth (PG) oocytes are distributed throughout the ovary with no other oocyte development stage present.</p

Spawning frequency (SF) estimates for female red snapper (<i>Lutjanus campechanus</i>) sampled from the Gulf of Mexico off Alabama (eastern Gulf) and Louisiana (western Gulf) in 1999, 2000, 2001, 2009 and 2010.

<p>Spawning frequency (SF) estimates for female red snapper (<i>Lutjanus campechanus</i>) sampled from the Gulf of Mexico off Alabama (eastern Gulf) and Louisiana (western Gulf) in 1999, 2000, 2001, 2009 and 2010.</p

Chi-Square test p-values for spawning frequency estimates compared among female red snapper (<i>Lutjanus campechanus</i>) sampled from Gulf of Mexico off Alabama (eastern Gulf) and Louisiana (western Gulf) in 1999, 2000, 2001, 2009 and 2010.

<p>Spawning frequency was estimated using the hydrated oocyte method, the post-ovulatory follicle method, and the time-calibrated method.</p

Mean batch fecundity estimates for female red snapper (<i>Lutjanus campechanus</i>) sampled from the Gulf of Mexico off Alabama (eastern Gulf) and Louisiana (western Gulf) in 1999, 2000, 2001, 2009 and 2010.

<p>Mean batch fecundity estimates for female red snapper (<i>Lutjanus campechanus</i>) sampled from the Gulf of Mexico off Alabama (eastern Gulf) and Louisiana (western Gulf) in 1999, 2000, 2001, 2009 and 2010.</p

Map of study sites.

<p>Sampling occurred east (off Alabama) and west (off Louisiana) of the Mississippi River. Map made using QGIS (2016). Mississippi River layer courtesy of USGS Watershed Boundary Dataset, available at <a href="http://nhd.usgs.gov/wbd.html" target="_blank">nhd.usgs.gov/wbd.html</a>.</p

Mean age (years), fork length (millimeters) and total wet weight (kilograms) of female red snapper (<i>Lutjanus campechanus</i>) sampled from the northern Gulf of Mexico (Gulf) in 1999, 2000, 2001, 2009 and 2010.

<p>Mean age (years), fork length (millimeters) and total wet weight (kilograms) of female red snapper (<i>Lutjanus campechanus</i>) sampled from the northern Gulf of Mexico (Gulf) in 1999, 2000, 2001, 2009 and 2010.</p

Analysis of covariance (ANCOVA) results testing for equality of batch fecundity regression slopes and y-intercepts among four sample groups of female red snapper (<i>Lutjanus campechanus</i>) collected from the Gulf of Mexico off Alabama (eastern Gulf) and Louisiana (western Gulf) in 1999, 2000, 2001 and 2009: EG1, eastern Gulf 1999–2001; EG2, eastern Gulf 2009; WG1, western Gulf 1999–2001; and WG2, western Gulf 2009.

<p>Regressions tested natural log-transformed batch fecundity against natural-log transformed fork length (millimeters), eviscerated body weight (grams) and age (years).</p

Annual fecundity estimates for female red snapper (<i>Lutjanus campechanus</i>) sampled from the Gulf of Mexico off Alabama (eastern Gulf) and Louisiana (western Gulf) in 1999, 2000, 2001, 2009 and 2010.

<p>Annual fecundity estimates for female red snapper (<i>Lutjanus campechanus</i>) sampled from the Gulf of Mexico off Alabama (eastern Gulf) and Louisiana (western Gulf) in 1999, 2000, 2001, 2009 and 2010.</p