Mississippi Alabama Sea Grant Consortium

Abstract Oyster reef living shorelines have been proposed as an effective alternative to traditional coastal defence structures (e.g. bulkheads, breakwaters), with the benefit that they may keep pace with sea‐level rise and provide co‐benefits, such as habitat provision. However, there remains uncertainty about the effectiveness of shoreline protection provided by oyster reefs, which limits their broader application. We draw evidence from studies along the east and gulf coasts of the United States, where much research and implementation of oyster reef restoration has occurred, to better define the existing gaps in our understanding of the use of restored oyster reefs for shoreline protection. We find potential disconnects between ecological and engineering functions of reefs. In response, we outline how engineering and ecological principles are used in the design of oyster reef living shorelines and highlight knowledge gaps where an integration of these disciplines will lead to their more effective application. Synthesis and applications . This work highlights the necessary steps to advance the application of oyster reef living shorelines. Importantly, future research should focus on appropriate designs and conditions needed for these structures to effectively protect our coasts from erosion, while supporting a sustainable oyster population, thereby providing actionable nature‐based alternatives for coastal defence to diverse end‐users.

One of the paramount goals of oyster reef living shorelines is to achieve sustained and adaptive coastal protection, which requires meeting ecological (i.e., develop a self-sustaining oyster population) and engineering (i.e., provide coastal defense) targets. In a large-scale comparison along the Atlantic and Gulf coasts of the United States, the efficacy of various designs of oyster reef living shorelines at providing wave attenuation was evaluated accounting for the ecological limitations of oysters with regard to inundation duration. A critical threshold for intertidal oyster reef establishment is 50% inundation duration. Living shorelines that spent less than one-half of the time (<50%) inundated were not considered suitable habitat for oysters, however, were effective at wave attenuation (68% reduction in wave height). Reefs that experienced >50% inundation were considered suitable habitat for oysters, but wave attenuation was similar to controls (no reef; ~5% reduction in wave height). Many of the oyster reef living shoreline approaches therefore failed to optimize the ecological and engineering goals. In both inundation regimes, wave transmission decreased with an increasing freeboard (difference between reef crest elevation and water level), supporting its importance in the wave attenuation capacity of oyster reef living shorelines. However, given that the reef crest elevation (and thus freeboard) should be determined by the inundation duration requirements of oysters, research needs to be refocused on understanding the implications of other reef parameters (e.g., width) for optimizing wave attenuation. A broader understanding of the reef characteristics and seascape contexts that result in effective coastal defense by oyster reefs is needed to inform appropriate design and implementation of oyster-based living shorelines globally.

Too often the public is provided with a bleak image of marine aquaculture facilities as industrial waste areas, depleting the natural environment and its biodiversity, and creating a desert from an ocean oasis. However, this image frequently has little rigorous scientific basis. Environmental problems have been found only in aquaculture settings with poor management plans, wasteful feeding strategies and where overproduction exceeds the carrying capacity of the natural environment causing the degradation of clean water - the very basis of a successful aquaculture venture. Cage aquaculture facilities provide habitats and nursery areas for juvenile and adult wild fish, and numerous invertebrate and algal species essential to sustaining healthy marine ecosystems and wild fish stocks. In addition, there is an unbalanced focus on marine animal husbandry causing a concomitant lack of appreciation for the positive environmental attributes of marine agronomy, a vital economic sector of global aquaculture. Indeed, tidal wetland, mangrove forest and seagrass restoration aquaculture - in addition to establishment and maintenance of oyster reefs - are important examples of aquaculture creating, enhancing and maintaining productive marine ecosystems, habitats and water quality in a long-term, sustainable manner. There is an urgent need for additional research to generate primary data on the positive and negative roles of marine aquaculture in the biogeochemical cycles, habitats and ecosystems of coastal oceans worldwide. The little research that has been done to date has documented numerous examples of marine aquaculture facilities that revitalize natural habitats, ecosystems and marine fisheries, as opposed to degrading the natural environment and competing with the wild fisheries sector. Without more comprehensive assessments and additional research, plans for the sustainable expansion of marine aquaculture will suffer from a lack of a scientific basis for rational planning and policy, and continue to be replaced by heresy, junk science and advocacy.

Abstract Climate change is altering species’ range limits and transforming ecosystems. For example, warming temperatures are leading to the range expansion of tropical, cold-sensitive species at the expense of their cold-tolerant counterparts. In some temperate and subtropical coastal wetlands, warming winters are enabling mangrove forest encroachment into salt marsh, which is a major regime shift that has significant ecological and societal ramifications. Here, we synthesized existing data and expert knowledge to assess the distribution of mangroves near rapidly changing range limits in the southeastern USA. We used expert elicitation to identify data limitations and highlight knowledge gaps for advancing understanding of past, current, and future range dynamics. Mangroves near poleward range limits are often shorter, wider, and more shrublike compared to their tropical counterparts that grow as tall forests in freeze-free, resource-rich environments. The northern range limits of mangroves in the southeastern USA are particularly dynamic and climate sensitive due to abundance of suitable coastal wetland habitat and the exposure of mangroves to winter temperature extremes that are much colder than comparable range limits on other continents. Thus, there is need for methodological refinements and improved spatiotemporal data regarding changes in mangrove structure and abundance near northern range limits in the southeastern USA. Advancing understanding of rapidly changing range limits is critical for foundation plant species such as mangroves, as it provides a basis for anticipating and preparing for the cascading effects of climate-induced species redistribution on ecosystems and the human communities that depend on their ecosystem services.

Abstract Coastal vegetated ecosystems are acknowledged for their capacity to sequester organic carbon (OC), known as blue C. Yet, blue C global accounting is incomplete, with major gaps in southern hemisphere data. It also shows a large variability suggesting that the interaction between environmental and biological drivers is important at the local scale. In southwest Atlantic salt marshes, to account for the space occupied by crab burrows, it is key to avoid overestimates. Here we found that southern southwest Atlantic salt marshes store on average 42.43 (SE = 27.56) Mg OC·ha −1 (40.74 (SE = 2.7) in belowground) and bury in average 47.62 g OC·m −2 ·yr −1 (ranging from 7.38 to 204.21). Accretion rates, granulometry, plant species and burrowing crabs were identified as the main factors in determining belowground OC stocks. These data lead to an updated global estimation for stocks in salt marshes of 185.89 Mg OC·ha −1 ( n = 743; SE = 4.92) and a C burial rate of 199.61 g OC·m −2 ·yr −1 ( n = 193; SE = 16.04), which are lower than previous estimates.

) faces varying levels of exploitation around the world due to its coastal distribution. Information regarding population connectivity is crucial to evaluate its conservation status and local fishing impacts. In this study, we sampled 922 putative Bull Sharks from 19 locations in the first global assessment of population structure of this cosmopolitan species. Using a recently developed DNA-capture approach (DArTcap), samples were genotyped for 3400 nuclear markers. Additionally, full mitochondrial genomes of 384 Indo-Pacific samples were sequenced. Reproductive isolation was found between and across ocean basins (eastern Pacific, western Atlantic, eastern Atlantic, Indo-West Pacific) with distinct island populations in Japan and Fiji. Bull Sharks appear to maintain gene flow using shallow coastal waters as dispersal corridors, whereas large oceanic distances and historical land-bridges act as barriers. Females tend to return to the same area for reproduction, making them more susceptible to local threats and an important focus for management actions. Given these behaviors, the exploitation of Bull Sharks from insular populations, such as Japan and Fiji, may instigate local decline that cannot readily be replenished by immigration, which can in turn affect ecosystem dynamics and functions. These data also supported the development of a genetic panel to ascertain the population of origin, which will be useful in monitoring the trade of fisheries products and assessing population-level impacts of this harvest.

In this mixed-methods study, we replicate a national Nature Conservancy survey on a regional scale to understand what local audiences know and believe about ecosystem services and conservation science. After the Deepwater Horizon oil spill in 2010, the Gulf Coast Ecosystem Restoration Council was created and charged with administering a large portion of the $13.7 billion in penalties (via the Gulf Coast Restoration Fund) for ecosystem restoration research and implementation programs. Almost as quickly as oil gushed into the Gulf, conservation organizations (local, state, federal and NGO) along the coast drafted proposals and requests for a piece of the funding. In December 2014, the State of Alabama submitted five proposed restoration projects with an estimated total cost of $54.2 million. Many of the projects use the language of ecosystem science, restoration and services to promote efforts to restore the ecosystem and economy of the Gulf Coast region. These phrases, once disciplinary jargon, are now heard in soundbites on the evening news and seen in the headlines of popular news sources (e.g. AL.com, Gulf Coast News Today, WKRG-Mobile and WPMI-Mobile). As this phraseology becomes more pervasive in this region, our specific goal is to investigate what the public knows and believes about one of the key concepts, ecosystem services, and identify who they trust to inform them about ecosystem services. This study confirms previous evidence that the public trusts scientists, but they do not always understand the language of science.

• Overview of the current state of algal bloom forecasting. • Algal bloom research relies on remote sensing data and products detecting blooms. • Data-driven approaches are the most used models in algal bloom forecast research. • Temperature, nutrients, wind, and bloom information are important input variables. • Literature is limited, being concentrated in specific regions and water bodies. Algal blooms are often major drivers of environmental and economic challenges. As these blooms increase in frequency and size, there is an increasing need for forecasting models to accurately predict their occurrence and progression. Such algal bloom forecast systems can provide early warnings to mitigate the harmful impacts on ecosystems and public health. This study presents an overview of the current progress for algal bloom forecasting (i.e., predicting the future occurrence, distribution, frequency, and intensity of algal blooms in water bodies) and emphasizes the need for research initiatives and future directions on this topic. Remote sensing, particularly ocean-color products, has emerged as a foundation for algal bloom monitoring and forecasting, providing critical spatial–temporal data to address the limitations of in situ measurements. Machine learning and deep learning models dominate recent developments, demonstrating their capabilities in capturing non-linear and complex dynamics and enhancing accuracy in forecasting. Forecast intervals used vary, ranging from daily forecasts to weeks, monthly, seasonal, and annual predictions. A relevant aspect of algal bloom forecasting is the input variables, and we identified the key inputs, including surface temperature, nitrogen and phosphorus concentrations, wind patterns, and previous/current bloom information. However, most studies are geographically concentrated in the Northern Hemisphere, specifically North America, Europe, and Asia, focusing on lakes and coastal waters, leaving tropical regions, rivers, reservoirs, and open oceans underexplored. Despite the advancement in this field, operational algal bloom forecasting systems are still scarce, particularly when compared to other environmental fields, such as meteorology and air quality forecasting. With new hyperspectral capabilities being developed, integrating these emerging technologies offers unprecedented opportunities to refine predictions, particularly for phytoplankton community composition and functional types. This study emphasizes the need to expand forecasting research to underrepresented regions and water body types, such as reservoirs and estuaries. Under current climate change scenarios, algal blooms may become more frequent and intense, and it is crucial to continuously develop and advance algal bloom research to support coastal and inland water management.

The expansion of black mangrove Avicennia germinans into historically smooth cordgrass Spartina alterniflora-dominated marshes with warming temperatures heralds the migration of the marsh-mangrove ecotone northward in the northern Gulf of Mexico. With this shift, A. germinans is expected to outcompete S. alterniflora where it is able to establish, offering another prevalent food source to first order consumers. In this study, we find A. germinans leaves to be preferable to chewing herbivores, but simultaneously, chewing herbivores cause more damage to S. alterniflora leaves. Despite higher nitrogen content, A. germinans leaves decomposed slower than S. alterniflora leaves, perhaps due to other leaf constituents or a different microbial community. Other studies have found the opposite in decomposition rates of the two species' leaf tissue. This study provides insights into basic trophic process, herbivory and decomposition, at the initial stages of black mangrove colonization into S. alterniflora salt marsh.

The Gulf of Mexico (GoM) region is prone to disasters, including recurrent oil spills, hurricanes, floods, industrial accidents, harmful algal blooms, and the current COVID-19 pandemic. The GoM and other regions of the U.S. lack sufficient baseline health information to identify, attribute, mitigate, and facilitate prevention of major health effects of disasters. Developing capacity to assess adverse human health consequences of future disasters requires establishment of a comprehensive, sustained community health observing system, similar to the extensive and well-established environmental observing systems. We propose a system that combines six levels of health data domains, beginning with three existing, national surveys and studies plus three new nested, longitudinal cohort studies. The latter are the unique and most important parts of the system and are focused on the coastal regions of the five GoM States. A statistically representative sample of participants is proposed for the new cohort studies, stratified to ensure proportional inclusion of urban and rural populations and with additional recruitment as necessary to enroll participants from particularly vulnerable or under-represented groups. Secondary data sources such as syndromic surveillance systems, electronic health records, national community surveys, environmental exposure databases, social media, and remote sensing will inform and augment the collection of primary data. Primary data sources will include participant-provided information via questionnaires, clinical measures of mental and physical health, acquisition of biological specimens, and wearable health monitoring devices. A suite of biomarkers may be derived from biological specimens for use in health assessments, including calculation of allostatic load, a measure of cumulative stress. The framework also addresses data management and sharing, participant retention, and system governance. The observing system is designed to continue indefinitely to ensure that essential pre-, during-, and post-disaster health data are collected and maintained. It could also provide a model/vehicle for effective health observation related to infectious disease pandemics such as COVID-19. To our knowledge, there is no comprehensive, disaster-focused health observing system such as the one proposed here currently in existence or planned elsewhere. Significant strengths of the GoM Community Health Observing System (CHOS) are its longitudinal cohorts and ability to adapt rapidly as needs arise and new technologies develop.

Biotelemetry applications have advanced our understanding of many highly migratory species, but present a challenge for species that suffer high capture and/or post-release stress. Failing to accurately characterize post-release fate can obfuscate our understanding of animal movement patterns and complicate the development of effective conservation and management plans. The great hammerhead (Sphyrna mokarran) is a long-lived, highly migratory shark listed by the International Union for the Conservation of Nature as Endangered. Accordingly, we used a combination of tags designed to report horizontal position estimates and verify post-release fate, to examine movements of great hammerheads in the northern Gulf of Mexico. Between May and September 2016, three individuals (one male and two females) were equipped with both fin-mounted smart position and temperature transmitting (SPOT) tags and survivorship pop-off archival tags (sPAT) to provide information on post-release fate. Tagged sharks measured 187 (F), 203 (M), and 250 (M) cm total length. All three sharks surfaced daily, yet individuals showed variability in vertical habitat use, with maximum daily depths ranging from 5 to 98 m. A single fin-mounted SPOT tag, attached to the smallest of the three sharks, reported position estimates over an 81-day period and moved a straight-line distance of approximately 400 km; however, the other two fin-mounted SPOT tags failed to generate position estimates. All three sPAT tags indicated post-release survival. Final positions of the sPAT tags from the two largest sharks suggested restricted horizontal movements (< 35 km). Despite their demonstrated utility on other shark species that frequent the surface, fin-mounted SPOT tags may not be the best option for tracking great hammerheads. In addition, our findings illustrate the value of double-tagging animals under certain conditions; notably, over the short monitoring period of this study, one of the three sharks tagged may have been incorrectly presumed dead had only a fin-mounted SPOT tag been used.

Abstract Sea Grant programs, both separately and in collaboration, have supported growth of the off‐bottom oyster industry in all five U.S. states in the Gulf of Mexico. Here, we review the history of the Mississippi‐Alabama Sea Grant Consortium (MASGC) investments in research and extension to support the growth of this industry (particularly in Alabama and Mississippi). Notably, the integration of applied research with strategic extension efforts was essential to the success of this industry. The MASGC enabled the establishment of commercial off‐bottom oyster aquaculture in Alabama and Mississippi using a series of strategic, outcomes‐focused investments in applied research and extension efforts through an array of partnerships. In Alabama, the first commercial off‐bottom oyster farm was established in 2009. The industry grew to 22 farms by 2020 with a farmgate value of nearly $1.5 million, employing over 30 full time equivalents (FTE). Over 12 farms have been established in Mississippi in the last two years. The MASGC also leveraged additional support from other funding agencies that has multiplied the outcomes and impacts.

Seasonal variability in environmental conditions is a strong determinant of animal migrations, but warming temperatures associated with climate change are anticipated to alter this phenomenon with unknown consequences. We used a 40-year fishery-independent survey to assess how a changing climate has altered the migration timing, duration and first-year survival of juvenile bull sharks (Carcharhinus leucas). From 1982 to 2021, estuaries in the western Gulf of Mexico (Texas) experienced a mean increase of 1.55°C in autumn water temperatures, and delays in autumn cold fronts by ca. 0.5 days per year. Bull shark migrations in more northern estuaries concomitantly changed, with departures 25-36 days later in 2021 than in 1982. Later, migrations resulted in reduced overwintering durations by up to 81 days, and the relative abundance of post-overwintering age 0-1 sharks increased by >50% during the 40-year study period. Yet, reductions in prey availability were the most influential factor delaying migrations. Juvenile sharks remained in natal estuaries longer when prey were less abundant. Long-term declines in prey reportedly occurred due to reduced spawning success associated with climate change based on published reports. Consequently, warming waters likely enabled and indirectly caused the observed changes in shark migratory behaviour. As water temperatures continue to rise, bull sharks in the north-western Gulf of Mexico could forgo their winter migrations in the next 50-100 years based on current trends and physiological limits, thereby altering their ecological roles in estuarine ecosystems and recruitment into the adult population. It is unclear if estuarine food webs will be able to support changing residency patterns as climate change affects the spawning success of forage species. We expect these trends are not unique to the western Gulf of Mexico or bull sharks, and migratory patterns of predators in subtropical latitudes are similarly changing at a global scale.

Understanding how interactions among microevolutionary forces generate genetic population structure of exploited species is vital to the implementation of management policies that facilitate persistence. Philopatry displayed by many coastal shark species can impact gene flow and facilitate selection, and has direct implications for the spatial scales of management. Here, genetic structure of the blacktip shark (Carcharhinus limbatus) was examined using a mixed-marker approach employing mitochondrial control region sequences and 4339 SNP-containing loci generated using ddRAD-Seq. Genetic variation was assessed among young-of-the-year sampled in 11 sites in waters of the United States in the western North Atlantic Ocean, including the Gulf of Mexico. Spatial and environmental analyses detected 68 nuclear loci putatively under selection, enabling separate assessments of neutral and adaptive genetic structure. Both mitochondrial and neutral SNP data indicated three genetically distinct units-the Atlantic, eastern Gulf, and western Gulf-that align with regional stocks and suggest regional philopatry by males and females. Heterogeneity at loci putatively under selection, associated with temperature and salinity, was observed among sites within Gulf units, suggesting local adaptation. Furthermore, five pairs of siblings were identified in the same site across timescales corresponding with female reproductive cycles. This indicates that females re-used a site for parturition, which has the potential to facilitate the sorting of adaptive variation among neighbouring sites. The results demonstrate differential impacts of microevolutionary forces at varying spatial scales and highlight the importance of conserving essential habitats to maintain sources of adaptive variation that may buffer species against environmental change.

Abstract The current COVID‐19 pandemic has forced the global higher education community to rapidly adapt to partially or fully online course offerings. For field‐ or laboratory‐based courses in ecological curricula, this presents unique challenges. Fortunately, a diverse set of active learning techniques exists, and these techniques translate well to online settings. However, limited guidance and resources exist for developing, implementing, and evaluating active learning assignments that fulfill specific objectives of ecology‐focused courses. To address these informational gaps, we (a) identify broad learning objectives across a variety of ecology‐focused courses, (b) provide examples, based on our collective online teaching experience, of active learning activities that are relevant to the identified ecological learning objectives, and (c) provide guidelines for successful implementation of active learning assignments in online courses. Using The Wildlife Society's list of online higher education ecology‐focused courses as a guide, we obtained syllabi from 45 ecology‐focused courses, comprising a total of 321 course‐specific learning objectives. We classified all course‐specific learning objectives into at least one of five categories: (a) Identification, (b) Application of Concepts/Hypotheses/Theories, (c) Management of Natural Resources, (d) Development of Professional Skills, or (e) Evaluation of Concepts/Practices. We then provided two examples of active learning activities for each of the five categories, along with guidance on their implementation in online settings. We suggest that, when based on sound pedagogy, active learning techniques can enhance the online student's experience by activating ecological knowledge.

Emerging diseases (ED) can have devastating effects on agriculture. Consequently, agricultural insurance for ED can develop if basic insurability criteria are met, including the capability to estimate the severity of ED outbreaks with associated uncertainty. The U.S. farm-raised channel catfish (Ictalurus punctatus) industry was used to evaluate the feasibility of using a disease spread simulation modeling framework to estimate the potential losses from new ED for agricultural insurance purposes. Two stochastic models were used to simulate the spread of ED between and within channel catfish ponds in Mississippi (MS) under high, medium, and low disease impact scenarios. The mean (95% prediction interval (PI)) proportion of ponds infected within disease-impacted farms was 7.6% (3.8%, 22.8%), 24.5% (3.8%, 72.0%), and 45.6% (4.0%, 92.3%), and the mean (95% PI) proportion of fish mortalities in ponds affected by the disease was 9.8% (1.4%, 26.7%), 49.2% (4.7%, 60.7%), and 88.3% (85.9%, 90.5%) for the low, medium, and high impact scenarios, respectively. The farm-level mortality losses from an ED were up to 40.3% of the total farm inventory and can be used for insurance premium rate development. Disease spread modeling provides a systematic way to organize the current knowledge on the ED perils and, ultimately, use this information to help develop actuarially sound agricultural insurance policies and premiums. However, the estimates obtained will include a large amount of uncertainty driven by the stochastic nature of disease outbreaks, by the uncertainty in the frequency of future ED occurrences, and by the often sparse data available from past outbreaks.

Plastic food service packaging represents a large source of plastic waste and marine debris. Currently, most food service business operators are resistant to changing to environmentally friendly alternatives due to perceived cost and loss of business due to passing these costs onto the consumer. To address these issues, we assessed the willingness of consumers to pay for plastic alternatives in both dine-in and takeout scenarios at restaurants in relation to levels of environmental concern, environmental identity, and demographics through a survey. Data were analyzed using a combination of descriptive statistics, regressions, and exploratory factor analyses. Of the 1371 survey responses, nearly 66% of respondents indicated they would be willing to pay 40 cents or more per person per meal at a restaurant for plastic alternatives and that this preference did not vary between dine-in and takeout scenarios. Additionally, education level and level of caring for the environment were the two most significant factors that increased willingness to pay for plastic alternatives.

Abstract Management of Gulf of Mexico Red Snapper Lutjanus campechanus has been a topic of much scientific debate and intensive public scrutiny. In response to political, public, and management desires for more robust data on Red Snapper populations, a gulfwide initiative commonly referred to as the “Great Red Snapper Count” (GRSC) was funded to estimate the absolute abundance of Red Snapper in the U.S. Gulf of Mexico. Here, we describe the results of an online survey designed to (1) characterize the social dimensions of Red Snapper anglers, (2) measure satisfaction with current Red Snapper populations and regulations, (3) assess overall patterns of awareness of the GRSC, and (4) evaluate the potential benefits of GRSC stakeholder engagement videos. A key finding of our survey was that awareness of the GRSC was associated with up to three times higher satisfaction with fisheries management. Through an in-survey experiment, we found that anglers that were presented a video on specific GRSC project components reported slightly higher management satisfaction than those presented an overview video or no video. Collectively, our results indicate that angler awareness, when underpinned by effective engagement and outreach activities, can enhance angler satisfaction.

Abstract Coastal ecosystems are highly vulnerable to the impacts of climate change and other stressors, including urbanization and overfishing. Consequently, distributions of coastal fish have begun to change, particularly in response to increasing temperatures linked to climate change. However, few studies have evaluated how natural and anthropogenic disturbances can alter species distributions in conjunction with geophysical habitat alterations, such as changes to land use and land cover (LU/LC). Here, we examine the spatiotemporal changes in the distribution of juvenile bull sharks ( Carcharhinus leucas ) using a multi-decadal fishery-independent survey of coastal Alabama. Using a boosted regression tree (BRT) modeling framework, we assess the covariance of environmental conditions (sea surface temperature, depth, salinity, dissolved oxygen, riverine discharge, Chl-a) as well as historic changes to LU/LC to the distribution of bull sharks. Species distribution models resultant from BRTs for early (2003–2005) and recent (2018–2020) monitoring periods indicated a mean increase in habitat suitability (i.e., probability of capture) for juvenile bull sharks from 0.028 to 0.082, concomitant with substantial increases in mean annual temperature (0.058°C/yr), Chl-a (2.32 mg/m 3 ), and urbanization (increased LU/LC) since 2000. These results align with observed five-fold increases in the relative abundance of juvenile bull sharks across the study period and demonstrate the impacts of changing environmental conditions on their distribution and relative abundance. As climate change persists, coastal communities will continue to change, altering the structure of ecological communities and the success of nearshore fisheries.

Understanding dispersal in large marine fauna is necessary for conservation, but movement patterns often vary widely by sex and life stage. In sharks, genetic studies have shown evidence of widespread male-biased dispersal, though tagging and tracking studies on the same populations show both sexes using site fidelity, including philopatry, and moving similar distances. We used a suite of microsatellite loci and DNA samples from 362 previously-tagged tiger sharks (Galeocerdo cuvier) in the northwestern Atlantic, including a large number of residential juveniles, to evaluate reproductive dispersal in light of demographic and published tracking data. We found that lumping size classes together resulted in genetic panmixia across sites, but systematic removal of large individuals showed significant population-level differentiation and three separate population clusters among juveniles less than 260 cm total length. Tests for relatedness found that 8.9% of our sample set was composed of first-order related pairs (N = 16), including several full siblings from different litters, a sign of multi-cycle genetic monogamy which carries implications for effective population size. By mapping genetic assignments of juveniles, we identified a signature of fine-scale genetic structure suggesting broad biparental site fidelity to reproductive habitat in the northeast Gulf of Mexico, which is concordant with both genetic and tracking data. Taken together, these findings demonstrate how lumping individuals from different life stages in genetic studies may obscure fine-scale genetic structure, confounding future conservation efforts.