The Northwest (NW) Atlantic porbeagle Lamna nasus is overfished and captured as bycatch in fisheries within the region. A comprehensive understanding of the population’s life history (e.g., reproduction) and habitat use, and the impact of capture with different gear types (e.g., post-release mortality) is needed to ensure effective fisheries management plans, develop bycatch mitigation strategies, and support stock recovery. This research used satellite tagging technologies to address gaps in knowledge needed to support management and conservation decisions for the NW Atlantic porbeagle. I provided the first estimate of post-release survival and recovery periods for immature porbeagles captured with rod-and-reel. Although survival was high (100%), juvenile porbeagles exhibited a recovery period in surface waters that may make them vulnerable to further fishing interactions. Next, I described the vertical habitat use of young porbeagles to recommend possible fishing modifications to reduce risk of capture. Young porbeagles spent more time in surface waters during summer compared to fall and during the night compared to day, suggesting that risk of capture may be reduced by setting gear deeper during summer and at night when this life stage’s behavior is reduced to the upper water column. Then, I provided an analysis of the seasonal and life stage-based habitat use of porbeagles. Space use was concentrated in continental shelf waters around Cape Cod, Massachusetts regardless of season and life stage. Given the relatively small and static high occupancy area overlaps with a high concentration of fishing activity, this region could be considered for spatial management of the NW Atlantic porbeagle. Finally, I used ultrasonography and satellite tagging to describe the three-dimensional habitat use of gravid porbeagles for the first time. Gravid porbeagles demonstrated seasonal differences in horizontal and vertical habitat use but spent most of the pupping season in waters southeast of Cape Cod or on Georges Bank, suggesting this region may be serving as a pupping ground for at least a portion of this population. Conservation efforts should focus on these important habitats to protect the next generation of porbeagles.

Porbeagles (Lamna nasus) are a highly commercially important shark species that is threatened with extinction due to overfishing. Mitochondrial DNA (mtDNA) displacement loop (D-loop) sequence data from 18 Northwest (NW) Atlantic and 30 Southwest (SW) Pacific porbeagles reveal that these regional populations have been genetically separated between 1.39 and 1.25 million years ago (MYA), a time frame which correlates with the end of the earth’s last cooling period. There is far greater genetic differentiation (FST = 0.835) between the NW and SW populations than among sharks within each population supporting a very high level of divergence. A lack of gene flow probably stemming from their limited distribution to cold water temperatures (-1oC to 15oC) has led to their genetic divergence. The NW Atlantic population exhibited fewer haplotypes than the SW Pacific population (2 vs 4). The mean nucleotide diversity value of the NW Atlantic population was also 50% lower (0.00143 vs. 0.00228). Male and female NW Atlantic individuals reflected virtually identical mean population diversity values (0.00393 vs 0.00399); however, females were prevalent near shorelines while the males were more often found in open waters. Of the three age groups within the NW Atlantic population, the immature individuals exhibited the greatest mean nucleotide diversity (0.00452), followed by the sub-adult group (0.00293) and the mature group (0.00288), suggesting that dispersion starts earlier in their life cycle and reduces as they get older. The porbeagle population biology, as revealed by D-loop sequence information, may have significant implications for the conservation efforts of this species. As differences in age-based and sex-based dispersion exist, it is important to understand the relative contributions of gene flow by adults of both sexes in order to implement more effective conservation strategies.

In my undergraduate honors thesis, I strive to convey my idea that dance is more than just movement, it’s one of the many artistic tools used to express emotions; which therefore has the power to storytell without words. It is my hope to create a captivating form of art that you not only view, but can interact and interpret.

The bull shark, Carcharhinus leucas, is a large species that it is commonly distributed worldwide in tropical and subtropical waters. Despite the bull sharks global distribution, little is known about its life history. In particular, the limited reproductive information suggests the bull shark is placental viviparous, assumed to have a biennial cycle, and that newborn pup nurseries are near the coast. In order to conserve and protect any species, an understanding of the habitats where reproductive events occur is needed. In order to better understand the habitat use in Biscayne bay, Fla, and whether certain areas are critical during the reproductive cycle of bull sharks, I will evaluate circulating levels of the hormones progesterone, estradiol, and testosterone using radioimmunoassay. These samples were collected by the University of Miami opportunistically between 2012-2020 shipped to Arizona State University, where they were analyzed. For my study a total of 73 mature samples, 27 females and 46 males, were collected over the sampling period. The results indicated that Biscayne bay is an important gestation area for bull sharks. The hormonal trends for males and females demonstrated an interesting reproductive cycle, which were further supported through other placental viviparous reproductive patterns. Females had a low level of estradiol throughout most of the year, besides in the summer where there were no sharks in the bay due to movement to estuaries. During their return to the bay, there was a peak in progesterone indicating early pregnancy. Male testosterone levels indicated that there was a production in sperm right before females speculated peak in estradiol.

This thesis utilizes GIS mapping to analyze the severity of four threats: ocean acidification, sea surface temperature, artisanal fishing, and destructive fishing, in conjunction with coral species distribution. This project produced maps that depicts each of these threats and shows the distribution of its severity. Compiling this data we can see that ocean acidification is the most pressing threat in the Caribbean to coral and that neither type of fishing really has a large effect. A species named Madracis carmabi is also flagged to be of particular concern as it is severely threatened by both ocean acidification and sea surface temperature.