Browsing by Author "Ferretti, Francesco"

Now showing 1 - 12 of 12
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    Analysing detection gaps in acoustic telemetry data to infer differential movement patterns in fish
    Williamson, Michael J.; Tebbs, Emma J.; Dawson, Terence P.; Curnick, David J.; Ferretti, Francesco; Carlisle, Aaron B.; Chapple, Taylor K.; Schallert, Robert J.; Tickler, David M.; Harrison, Xavier A.; Block, Barbara A.; Jacoby, David M. P. (2021-03)
    A wide array of technologies are available for gaining insight into the movement of wild aquatic animals. Although acoustic telemetry can lack the fine-scale spatial resolution of some satellite tracking technologies, the substantially longer battery life can yield important long-term data on individual behavior and movement for low per-unit cost. Typically, however, receiver arrays are designed to maximize spatial coverage at the cost of positional accuracy leading to potentially longer detection gaps as individuals move out of range between monitored locations. This is particularly true when these technologies are deployed to monitor species in hard-to-access locations. Here, we develop a novel approach to analyzing acoustic telemetry data, using the timing and duration of gaps between animal detections to infer different behaviors. Using the durations between detections at the same and different receiver locations (i.e., detection gaps), we classify behaviors into "restricted" or potential wider "out-of-range" movements synonymous with longer distance dispersal. We apply this method to investigate spatial and temporal segregation of inferred movement patterns in two sympatric species of reef shark within a large, remote, marine protected area (MPA). Response variables were generated using network analysis, and drivers of these movements were identified using generalized linear mixed models and multimodel inference. Species, diel period, and season were significant predictors of "out-of-range" movements. Silvertip sharks were overall more likely to undertake "out-of-range" movements, compared with gray reef sharks, indicating spatial segregation, and corroborating previous stable isotope work between these two species. High individual variability in "out-of-range" movements in both species was also identified. We present a novel gap analysis of telemetry data to help infer differential movement and space use patterns where acoustic coverage is imperfect and other tracking methods are impractical at scale. In remote locations, inference may be the best available tool and this approach shows that acoustic telemetry gap analysis can be used for comparative studies in fish ecology, or combined with other research techniques to better understand functional mechanisms driving behavior.
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    Design and Model-based Approaches for Estimating Abundance of American Horseshoe Crab
    Wong, Chad Christopher (Virginia Tech, 2024-01-24)
    The American horseshoe crab (HSC), Limulus polyphemus, is one of four species of horseshoe crabs found throughout the world, and the only one found in North America. It is an economically and ecologically important species throughout its native range from Maine to the Yucatan Peninsula. Harvested for fertilizer and livestock feed in the 19th century, the species is now harvested as bait for whelk and eel fisheries, and for their blood by the biomedical industry. The Atlantic States Marine Fisheries Commission (ASMFC) started to formally manage HSC in 1998 with its Interstate Fisheries Management Plan (IFMP). Unique emphasis and harvest limits have been placed on the Delaware Bay stock, as it is commercially exploited and a critical food source for the threatened red knot, Calidris canutus rufa. Previously, estimates of relative and total abundance of HSC in the Delaware Bay area were based on a design-based approach using a stratified random sampling design. In Chapter 1 of this work, I developed hurdle models for each of the six HSC demographic groups to standardize catch-per-unit-effort (CPUE) and estimate relative abundance using a model-based approach. It was determined that while the two approaches resulted in mostly convergent estimates of relative abundance, external factors such as month, time-of-day, and average depth have major effects on the observed CPUE of all demographic groups. Chapter 2 involved the development of hurdle models for the three species of bycatch frequently caught in our trawls, channeled whelk (Busysotypus canaliculatus), knobbed whelk (Busycon carica), and summer flounder (Paralichthys dentatus). It was found that channeled whelk relative abundance has been at a historical low since 2016, while summer flounder has been at a consistent high. Recent estimates of knobbed whelk relative abundance have been less variable than previously seen, with estimates since 2016 being similar to those seen before 2012. These results provide the first estimates for whelk population trends in the mid-Atlantic region and add to the growing knowledge of summer flounder relative abundance in the area. In Chapter 3, I applied the hurdle models developed in Chapter 1 to estimate the total abundance of HSC in the Delaware Bay area. For this work, I developed two spatio-temporal variograms to estimate bottom temperature and bottom salinity at unmeasured cells per month in the time series. The results showed that night estimates of total abundance were consistently higher than daytime estimates, and estimates from September or November resulted in the highest estimated catch for all demographic groups. The results suggest that when comparing September model-based estimates at night to those of the design-based approach, nearly a third of all previous design-based estimates significantly underestimated the total abundance of HSC in the Delaware Bay area. This result suggests that the ASMFC can recommend increased harvest limits for mature individuals if that action aligns with the goals of their adaptive resource management (ARM) framework.
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    Detecting Mediterranean White Sharks with Environmental DNA
    Jenrette, Jeremy F.; Jenrette, Jennifer L.; Truelove, N. Kobun; Moro, Stefano; Dunn, Nick I.; Chapple, Taylor K.; Gallagher, Austin J.; Gambardella, Chiara; Schallert, Robert; Shea, Brendan D.; Curnick, David J.; Block, Barbara A.; Ferretti, Francesco (The Oceanography Society, 2023-01)
    The white shark (Carcharodon carcharias) is a globally distributed, ecologically important top predator whose biology and population dynamics are challenging to study. Basic biological parameters remain virtually unknown in the Mediterranean Sea due to its historically low population density, dwindling population size, and lack of substantial sightings. White sharks are considered Critically Endangered in the Mediterranean Sea, and recent analyses suggest that the population has declined by 52% to 96% from historical levels in different Mediterranean sectors (Moro et al., 2020). Thus, white shark sightings dating back to 1860 are being used to estimate population trajectories throughout the entire region. Though the population size is unknown, remaining individuals are thought to be primarily restricted to a handful of hotspots deemed important for their reproduction and foraging. One of these hypothesized hotspots is the Sicilian Channel, which accounts for 19% of total historical sightings.
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    Emergent research and priorities for shark and ray conservation
    Jorgensen, Salvador J.; Micheli, Fiorenza; White, Timothy D.; Van Houtan, Kyle S.; Alfaro-Shigueto, Joanna; Andrzejaczek, Samantha; Arnoldi, Natalie S.; Baum, Julia K.; Block, Barbara; Britten, Gregory L.; Butner, Cheryl; Caballero, Susana; Cardeñosa, Diego; Chapple, Taylor K.; Clarke, Shelley; Cortés, Enric; Dulvy, Nicholas K.; Fowler, Sarah; Gallagher, Austin J.; Gilman, Eric; Godley, Brendan J.; Graham, Rachel T.; Hammerschlag, Neil; Harry, Alastair V.; Heithaus, Michael R.; Hutchinson, Melanie; Huveneers, Charlie; Lowe, Chris G.; Lucifora, Luis O.; MacKeracher, Tracy; Mangel, Jeffrey C.; Barbosa Martins, Ana Paula; McCauley, Douglas J.; McClenachan, Loren; Mull, Christopher; Natanson, Lisa J.; Pauly, Daniel; Pazmiño, Diana A.; Pistevos, Jennifer C.A.; Queiroz, Nuno; Roff, George; Shea, Brendan D.; Simpfendorfer, Colin A.; Sims, David W.; Ward-Paige, Christine; Worm, Boris; Ferretti, Francesco (Inter-Research, 2022-02-28)
    Over the past 4 decades there has been a growing concern for the conservation status of elasmobranchs (sharks and rays). In 2002, the first elasmobranch species were added to Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). Less than 20 yr later, there were 39 species on Appendix II and 5 on Appendix I. Despite growing concern, effective conservation and management remain challenged by a lack of data on population status for many species, human−wildlife interactions, threats to population viability, and the efficacy of conservation approaches. We surveyed 100 of the most frequently published and cited experts on elasmobranchs and, based on ranked responses, prioritized 20 research questions on elasmobranch conservation. To address these questions, we then convened a group of 47 experts from 35 institutions and 12 countries. The 20 questions were organized into the following broad categories: (1) status and threats, (2) population and ecology, and (3) conservation and management. For each section, we sought to synthesize existing knowledge, describe consensus or diverging views, identify gaps, and suggest promising future directions and research priorities. The resulting synthesis aggregates an array of perspectives on emergent research and priority directions for elasmobranch conservation.
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    The importance of migratory connectivity for global ocean policy
    Dunn, Daniel C.; Harrison, Autumn-Lynn; Curtice, Corrie; DeLand, Sarah; Donnelly, Ben; Fujioka, Ei; Heywood, Eleanor; Kot, Connie Y.; Poulin, Sarah; Whitten, Meredith; Akesson, Susanne; Alberini, Amalia; Appeltans, Ward; Manuel Arcos, Jos; Bailey, Helen; Ballance, Lisa T.; Block, Barbara A.; Blondin, Hannah; Boustany, Andre M.; Brenner, Jorge; Catry, Paulo; Cejudo, Daniel; Cleary, Jesse; Corkeron, Peter; Costa, Daniel P.; Coyne, Michael; Crespo, Guillermo Ortuno; Davies, Tammy E.; Dias, Maria P.; Douvere, Fanny; Ferretti, Francesco; Formia, Angela; Freestone, David; Friedlaender, Ari S.; Frisch-Nwakanma, Heidrun; Frojan, Christopher Barrio; Gjerde, Kristina M.; Glowka, Lyle; Godley, Brendan J.; Gonzalez-Solis, Jacob; Granadeiro, Jose Pedro; Gunn, Vikki; Hashimoto, Yuriko; Hawkes, Lucy M.; Hays, Graeme C.; Hazin, Carolina; Jimenez, Jorge; Johnson, David E.; Luschi, Paolo; Maxwell, Sara M.; McClellan, Catherine; Modest, Michelle; di Sciara, Giuseppe Notarbartolo; Palacio, Alejandro Herrero; Palacios, Daniel M.; Pauly, Andrea; Rayner, Matt; Rees, Alan F.; Salazar, Erick Ross; Secor, David; Sequeira, Ana MM M.; Spalding, Mark; Spina, Fernando; Van Parijs, Sofie; Wallace, Bryan; Varo-Cruz, Nuria; Virtue, Melanie; Weimerskirch, Henri; Wilson, Laurie; Woodward, Bill; Halpin, Patrick N. (Royal Society, 2019-09-18)
    The distributions of migratory species in the ocean span local, national and international jurisdictions. Across these ecologically interconnected regions, migratory marine species interact with anthropogenic stressors throughout their lives. Migratory connectivity, the geographical linking of individuals and populations throughout their migratory cycles, influences how spatial and temporal dynamics of stressors affect migratory animals and scale up to influence population abundance, distribution and species persistence. Population declines of many migratory marine species have led to calls for connectivity knowledge, especially insights from animal tracking studies, to be more systematically and synthetically incorporated into decision-making. Inclusion of migratory connectivity in the design of conservation and management measures is critical to ensure they are appropriate for the level of risk associated with various degrees of connectivity. Three mechanisms exist to incorporate migratory connectivity into international marine policy which guides conservation implementation: site-selection criteria, network design criteria and policy recommendations. Here, we review the concept of migratory connectivity and its use in international policy, and describe the Migratory Connectivity in the Ocean system, a migratory connectivity evidence-base for the ocean. We propose that without such collaboration focused on migratory connectivity, efforts to effectively conserve these critical species across jurisdictions will have limited effect.
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    Interactions Between a Large Marine Protected Area, Pelagic Tuna and Associated Fisheries
    Curnick, David J.; Collen, Ben; Koldewey, Heather J.; Jones, Kate E.; Kemp, Kirsty M.; Ferretti, Francesco (2020-05-14)
    The efficacy of large marine protected areas (MPA) for the conservation of mobile pelagic species is widely debated. Here, we quantified spatial and temporal trends in standardized catch per unit effort (CPUE) of two target pelagic species, yellowfin (Thunnus albacares) and bigeye tuna (Thunnus obesus) in the Indian Ocean to analyze the impact of the British Indian Ocean Territory (BIOT) MPA's creation in 2010. We applied generalized additive mixed effects models to historical BIOT longline fishery logbooks and official catch and effort statistics from the Indian Ocean Tuna Commission (IOTC) to standardize CPUEs and to evaluate long-term trends and distribution patterns across the equatorial Indian Ocean. We find that trends in population indices from within BIOT prior to the MPA's establishment mirror those of the wider Indian Ocean. We also suggest that there may be behavioral plasticity within the yellowfin tuna stock, with some individuals possibly undertaking alternative migration patterns or exhibiting residency behavior within BIOT. Yet, we find no direct evidence of any improvement in standardized CPUE indices of either species in the area surrounding the BIOT MPA, nearly 8 years after its establishment. The average size of yellowfin and bigeye tunas caught both increased after the MPA's establishment. These patterns were also evident across the equatorial Indian Ocean, suggesting that any MPA effect is in combination with other regional drivers, such as behavioral changes in the fishing fleets in response to the threat of Somali Piracy. We therefore conclude that BIOT MPA may be providing local conservation value to tunas, but it is not significant enough to halt the overall regional decline in yellowfin tuna stocks. Thus, we emphasize that large MPAs should be considered in conjunction with other fishery management regulations and wider regional processes, rather than as a silver bullet, in order to provide the conservation and management benefits needed for mobile species like tunas.
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    Long-term change in a meso-predator community in response to prolonged and heterogeneous human impact
    Ferretti, Francesco; Osio, G. C.; Jenkins, C. J.; Rosenberg, A. A.; Lotze, H. K. (Springer Nature, 2013-01-28)
    Sharks and rays' abundance can decline considerably with fishing. Community changes, however, are more complex because of species interactions, and variable vulnerability and exposure to fishing. We evaluated long-term changes in the elasmobranch community of the Adriatic Sea, a heavily exploited Mediterranean basin where top-predators have been strongly depleted historically, and fishing developed unevenly between the western and eastern side. Combining and standardizing catch data from five trawl surveys from 1948-2005, we estimated abundance trends and explained community changes using life histories, fish-market and effort data, and historical information. We identified a highly depleted elasmobranch community. Since 1948, catch rates have declined by >94% and 11 species ceased to be detected. The exploitation history and spatial gradients in fishing pressure explained most patterns in abundance and diversity, including the absence of strong compensatory increases. Ecological corridors and large-scale protected areas emerged as potential management options for elasmobranch conservation.
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    Opportunities from citizen science for shark conservation, with a focus on the Mediterranean Sea
    Bargnesi, F.; Lucrezi, S.; Ferretti, Francesco (2020-01-01)
    The Mediterranean Sea is a hotspot for shark conservation. A decline in large pelagic shark populations has been observed in this vast region over the last 50 years and a lack of data on the local population status of various species has been pointed out. Throughout history, the relation between people and sharks has been revolving around a mixture of mystery, fear, and attraction. Recently, however, a remunerative ecotourism industry has been growing in areas of shark aggregation globally. This growth has been accompanied by the establishment of a citizen science (CS) movement aimed to engage and recruit ecotourists in data collection for shark research. Several CS projects have generated interesting results in terms of scientific findings and public engagement. In the Mediterranean Sea, shark aggregations are not as relevant to support locally-focused CS actions on shark diving sites as in other parts of the world. However, a series of other initiatives are taking place and CS could offer an excellent opportunity for shark conservation in the Mediterranean Sea. The dramatic decline of shark populations shown in the region calls for alternative ways to collect data on species distributions and abundance. Obtaining such data to set proper conservation and management plans for sharks in the Mediterranean Sea will be possible if existing CS initiatives collaborate and coordinate, and CS is widely acknowledged and deployed as a valuable tool for public education, engagement, and scientific discovery. After providing an overview of multiple facets of the relationship between humans and sharks, we focus on the possibility of exploiting new technologies and attitudes toward sharks among some groups of ocean users to boost participatory research. CS is a great opportunity for shark science, especially for areas such as the Mediterranean Sea and for large pelagic sharks whose populations are highly impacted.
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    Quantifying longline bycatch mortality for pelagic sharks in western Pacific shark sanctuaries
    Shea, Brendan D.; Gallagher, Austin J.; Bomgardner, Lindsay K.; Ferretti, Francesco (American Association for the Advancement of Science, 2023-08)
    Marine protected areas are increasingly touted for their role in conserving large marine predators such as sharks, but their efficacy is debated. Seventeen “shark sanctuaries” have been established globally, but longline fishing continues within many such jurisdictions, leading to unknown levels of bycatch mortality levels. Using public data from Global Fishing Watch and Regional Fisheries Management Organizations, we quantified longline fishing within eight shark sanctuaries and estimated pelagic shark catch and mortality for seven pelagic shark species. Sanctuary mortality ranged from 600 individuals (Samoa) to 36,256 individuals (Federated States of Micronesia), equivalent to ~5% of hypothesized sustainable levels for blue sharks to ~40% for silky sharks, with high mortality levels in the Federated States of Micronesia, Palau, and the Marshall Islands. Unsustainable mortality rates were exceeded for silky sharks in two sanctuaries, highlighting a need for additional stock assessments and implementation of bycatch reduction measures. Big data integration workflows represent a transformative tool in fisheries management, particularly for data-poor species.
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    Shark detection and classification with machine learning
    Jenrette, Jeremy; Liu, Zac; Chimote, Pranav; Hastie, Trevor; Fox, Edward; Ferretti, Francesco (Elsevier, 2022-07-01)
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    Shark fin trade bans and sustainable shark fisheries
    Ferretti, Francesco; Jacoby, David M. P.; Pfleger, Mariah O.; White, Timothy D.; Dent, Felix; Micheli, Fiorenza; Rosenberg, Andrew A.; Crowder, Larry B.; Block, Barbara A. (2020)
    The U.S. Congress is currently discussing the Shark Fin Sales Elimination Act to eliminate shark fin trade at the federal level. This bill was introduced in 2017 and has been proceeding very slowly in Congress because of mixed reviews from the scientific community. Debate exists on whether shark conservation and management are effectively addressed with tightened trade controls for imported shark products or blanket bans that outright end U.S. participation in the shark fin trade. Here we contribute to this debate with a review and analysis of economic, nutritional, ethical, and legal arguments, as well as of the shark fisheries status and shark fin trade. We show that the United States has a limited commercial interest in shark fisheries and contributes to the shark fin trade mainly as a facilitator. A fin trade ban has few tangible economic drawbacks but would have a considerable conservation impact. While making all shark fisheries sustainable is the ultimate goal, in practice this objective is far from achievable everywhere in the world. Conversely, banning shark fin trade is an interim measure that nations like the United States can take with negligible cost and can truly impact the biggest driver of shark exploitation globally.
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    Shark movement strategies influence poaching risk and can guide enforcement decisions in a large, remote marine protected area
    Jacoby, David M. P.; Ferretti, Francesco; Freeman, Robin; Carlisle, Aaron B.; Chapple, Taylor K.; Curnick, David J.; Dale, Jonathan J.; Schallert, Robert J.; Tickler, David; Block, Barbara A. (British Ecological Society, 2020-05-12)
    Large, remote marine protected areas (MPAs) containing both reef and pelagic habitats, have been shown to offer considerable refuge to populations of reef‐associated sharks. Many large MPAs are, however, impacted by illegal fishing activity conducted by unlicensed vessels. While enforcement of these reserves is often expensive, it would likely benefit from the integration of ecological data on the mobile animals they are designed to protect. Consequently, shark populations in some protected areas continue to decline, as they remain a prime target for illegal fishers. To understand shark movements and their vulnerability to illegal fishing, 3 years of acoustic tracking data, from 101 reef‐associated sharks, were analysed as movement networks to explore the predictability of movement patterns and identify key movement corridors within the British Indian Ocean Territory (BIOT) MPA. We examined how space use and connectivity overlap with spatially explicit risk of illegal fishing, through data obtained from the management consultancy enforcing the MPA. Using individual‐based models, the movement networks of two sympatric shark species were efficiently predicted with distance‐decay functions (>95% movements accurately predicted). Model outliers were used to highlight the locations with unexpectedly high movement rates where MPA enforcement patrols might most efficiently mitigate predator removal. Activity space estimates and network metrics illustrate that silvertip sharks were more dynamic, less resident and link larger components of the MPA than grey reef sharks. However, we show that this behaviour potentially enhances their exposure to illegal fishing activity. Synthesis and applications. Marine protected area (MPA) enforcement strategies are often limited by resources. The British Indian Ocean Territory MPA, one of the world's largest ‘no take’ MPAs, has a single patrol vessel to enforce 640,000 km2 of open ocean, atoll and reef ecosystems. We argue that to optimize the patrol vessel search strategy and thus enhance their protective capacity, ecological data on the space use and movements of desirable species, such as large‐bodied reef predators, must be incorporated into management plans. Here, we use electronic tracking data to evaluate how shark movement dynamics influence species mortality trajectories in exploited reef ecosystems. In doing so we discuss how network analyses of such data might be applied for protected area enforcement.