Von Bertalanffy growth functions for smalltooth sawfish.

<p>A) Size at fractional age for smalltooth sawfish samples collected in south Florida and aged via analysis of vertebrae centra thin sections. Plotted line is a von Bertalanffy growth function (VBGF) fit to the data with the method of least squares. Parameter estimates for the function are 4.48 m for L_∞, 0.219 y⁻¹ for k, and −0.81 years for t₀. B) Comparison of VBGF function estimated in this study with those estimated by Simpfendorfer et al. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone.0047850-Simpfendorfer2" target="_blank">[11]</a> with length frequency data (ELEFAN seasonal; PROJMAT non-seasonal).</p

Thin sections of vertebrae from three sawfish.

<p>Digital images of thin sections of smalltooth sawfish vertebrae centra from carcasses opportunistically sampled in south Florida from 2003 through 2012. Vertebrae were from A) a 1.50 m TL male (fish 8 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone-0047850-t001" target="_blank">Table 1</a>), B) a 2.22 m TL female (fish 7), and C) a 4.35 m TL female (fish 13). Black circles indicate opaque zones, with the first opaque zone in each section being the natal mark following birth.</p

Association between Sr:Ca and estuarine nursery bottom salinity.

<p>Correspondence between Sr:Ca versus estimated date and bottom salinity versus date A) a 1.96 m female smalltooth sawfish (fish 10 in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone-0047850-t001" target="_blank">Table 1</a>) whose carcass was collected in the Caloosahatchee River. B) Continuous bottom salinity data in the Caloosahatchee River during the time period depicted in A. C) a 2.22 m female (fish 7) whose carcass was collected near the mouth of the Turner River in Chokoloskee Bay. D) Continuous bottom salinity data in the Turner River during the time period depicted in C. Sr:Ca data are presented from the natal mark to the edge of the vertebra section. Gray circles in each panel indicate individual measurements, red circles indicate opaque bands, and black lines indicate loess regression fits to the data.</p

Trends in calcium versus phosphorus count data.

<p>Trends in Ca and P count data (cps  =  counts per second) from laser ablation-inductively coupled plasma-mass spectrometry transects across vertebral sections of three smalltooth sawfish. Data were smoothed by computing 5-spot moving averages prior to plotting lines. Red circles indicate location of opaque bands. Panel labels correspond to fish sample numbers in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone-0047850-t001" target="_blank">Table 1</a>.</p

Collection and biological information for 15 sawfish carcasses opportunistically sampled in south Florida from 2003 to 2012.

<p>Maturity: M =  mature, I =  immature. Exact locations of collection are provided on <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone-0047850-g001" target="_blank">Figure 1</a>.</p

Trends in Sr:Ca across vertebrae sections.

<p>Trends in Sr:Ca across smalltooth sawfish vertebrae sections analyzed with laser ablation-inductively coupled plasma-mass spectrometry. Gray circles in each panel indicate individual measurements, while black lines indicate loess regression fits to the data. Red circles indicate location of subsequent opaque bands. Panel labels correspond to fish sample numbers in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0047850#pone-0047850-t001" target="_blank">Table 1</a>.</p

Seasonal Distribution and Historic Trends in Abundance of White Sharks, <i>Carcharodon carcharias</i>, in the Western North Atlantic Ocean

<div><p>Despite recent advances in field research on white sharks (<i>Carcharodon carcharias</i>) in several regions around the world, opportunistic capture and sighting records remain the primary source of information on this species in the northwest Atlantic Ocean (NWA). Previous studies using limited datasets have suggested a precipitous decline in the abundance of white sharks from this region, but considerable uncertainty in these studies warrants additional investigation. This study builds upon previously published data combined with recent unpublished records and presents a synthesis of 649 confirmed white shark records from the NWA compiled over a 210-year period (1800-2010), resulting in the largest white shark dataset yet compiled from this region. These comprehensive records were used to update our understanding of their seasonal distribution, relative abundance trends, habitat use, and fisheries interactions. All life stages were present in continental shelf waters year-round, but median latitude of white shark occurrence varied seasonally. White sharks primarily occurred between Massachusetts and New Jersey during summer and off Florida during winter, with broad distribution along the coast during spring and fall. The majority of fishing gear interactions occurred with rod and reel, longline, and gillnet gears. Historic abundance trends from multiple sources support a significant decline in white shark abundance in the 1970s and 1980s, but there have been apparent increases in abundance since the 1990s when a variety of conservation measures were implemented. Though the white shark's inherent vulnerability to exploitation warrants continued protections, our results suggest a more optimistic outlook for the recovery of this iconic predator in the Atlantic.</p></div

White shark seasonal distribution.

<p>Distribution of white shark presence records (white circles) in the NWA during (a) winter, (b) spring, (c) summer, and (d) fall. Positions are overlaid on seasonal average SST conditions (1985–2001). The 200 m bathymetric contour is displayed to delineate the edge of the continental shelf. CC  =  Cape Cod, NYB  =  New York Bight, CH  =  Cape Hatteras, FL  =  Florida, GOM  =  Gulf of Mexico, and CS  =  Caribbean Sea.</p

White shark relative abundance.

<p>White shark indices of abundance (index/mean) standardized using a zero-inflated Poisson model plotted by year for three time series: NEFSC LL  =  Northeast Fisheries Science Center fishery-independent longline surveys, TOURN  =  NEFSC tournament database, and OBS LL  =  observer program of the directed shark longline fishery. Trend lines are best fit regression models of the standardized data (second order polynomial for NEFSC LL and exponential for TOURN and OBS), using R² values and considering the biology of the white shark. The dashed red line indicates the year of the first fishery management plan (FMP) for Atlantic sharks in 1993 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0099240#pone.0099240-National2" target="_blank">[77]</a> and the solid red line indicates the year that white sharks were listed as a NMFS prohibited species in 1997 <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0099240#pone.0099240-National1" target="_blank">[21]</a>.</p

White shark relative abundance trend.

<p>Time series of white shark relative abundance in the NWA as estimated from hierarchical analysis. The continuous black line gives the posterior mean, and the shaded area represents a 95% credible interval about the time series. The red line is the estimated trend based on locally weighted polynomial regression using the LOWESS smoother.</p