Long-term monitoring provides insight into estuarine top predator (Carcharhinus leucas) resilience following an extreme weather event

2020 ◽  
Vol 639 ◽  
pp. 169-183
Author(s):  
P Matich ◽  
BA Strickland ◽  
MR Heithaus
Keyword(s):  
Habitat Use ◽  
Acoustic Telemetry ◽  
South Florida ◽  
Behavioral Variability ◽  
Catch Per Unit Effort ◽  
Ontogenetic Shifts ◽  
Carcharhinus Leucas ◽  
Acute Disturbance ◽  
Cold Snap

Chronic environmental change threatens biodiversity, but acute disturbance events present more rapid and immediate threats. In 2010, a cold snap across south Florida had wide-ranging impacts, including negative effects on recreational fisheries, agriculture, and ecological communities. Here, we use acoustic telemetry and historical longline monitoring to assess the long-term implications of this event on juvenile bull sharks Carcharhinus leucas in the Florida Everglades. Despite the loss of virtually all individuals (ca. 90%) within the Shark River Estuary during the cold snap, the catch per unit effort (CPUE) of age 0 sharks on longlines recovered through recruitment within 6-8 mo of the event. Acoustic telemetry revealed that habitat use patterns of age 0-2 sharks reached an equilibrium in 4-6 yr. In contrast, the CPUE and habitat use of age 3 sharks required 5-7 yr to resemble pre-cold snap patterns. Environmental conditions and predation risk returned to previous levels within 1 yr of the cold snap, but abundances of some prey species remained depressed for several years. Reduced prey availability may have altered the profitability of some microhabitats after the cold snap, leading to more rapid ontogenetic shifts to marine waters among sharks for several years. Accelerated ontogenetic shifts coupled with inter-individual behavioral variability of bull sharks likely led to a slower recovery rate than predicted based on overall shark CPUE. While intrinsic variation driven by stochasticity in dynamic ecosystems may increase the resistance of species to chronic and acute disturbance, it may also increase recovery time in filling the diversity of niches occupied prior to disturbance if resistive capacity is exceeded.

A multi-faceted approach for quantifying the estuarine - nearshore transition in the life cycle of the bull shark, Carcharhinus leucas

2011 ◽  
Vol 62 (12) ◽  
pp. 1421 ◽  
Author(s):  
J. M. Werry ◽  
S. Y. Lee ◽  
N. M. Otway ◽  
Y. Hu ◽  
W. Sumpton
Keyword(s):  
Habitat Use ◽  
Acoustic Telemetry ◽  
Inductively Coupled Plasma ◽  
Stomach Contents ◽  
Inductively Coupled ◽  
Carcharhinus Leucas ◽  
Bull Shark ◽  
Plasma Mass Spectrometry ◽  
Shark Attacks ◽  
Δ15n And Δ13c

Understanding the ontogenetic habitat linkages of sharks is important for conservation and managing human interactions. We used acoustic telemetry, catch data, elemental and stable isotope signatures and dietary analyses to investigate ontogenetic habitat use in south-east Queensland, Australia, by the bull shark Carcharhinus leucas, a IUCN ‘near-threatened’ species that is implicated in many shark attacks on humans in urban estuaries. Sequential analyses for δ15N and δ13C of vertebrae from five adult C. leucas and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) for elemental composition from 23 C. leucas, including a pregnant female, were also used to trace ontogenetic habitat dependence. Acoustic telemetry indicated large juvenile and subadult C. leucas remained in estuarine habitats. δ15N values across shark vertebrae showed an ontogenetic shift in diet with total length (TL), confirmed by stomach contents. LA-ICPMS data reflected the ontogenetic movements of C. leucas from natal habitats. Differences among adults were gender related. Shifts in habitat use by subadults were correlated with a sigmoidal δ13C relationship with TL. C. leucas have a multipartite, stage-specific dependency in their transition between habitats along the freshwater–estuarine–marine continuum, making them particularly susceptible to the habitat alteration that is occurring globally.

Long-term trends of bull shark (Carcharhinus leucas) in estuarine waters of Texas, USA

2013 ◽  
Vol 70 (1) ◽  
pp. 13-21 ◽  
Author(s):  
John T. Froeschke ◽  
Bridgette F. Froeschke ◽  
Charlotte M. Stinson
Keyword(s):  
Catch Per Unit Effort ◽  
Ecosystem Effects ◽  
Carcharhinus Leucas ◽  
Bull Shark ◽  
Mean Size ◽  
Long Term Trends ◽  
Monitoring Survey ◽  
Standardized Index ◽  
Federal Management

Increases in standardized catch per unit effort (CPUE) and mean length of bull shark (Carcharhinus leucas) were observed in coastal estuaries over a 35-year period (1976–2010). Trends in abundance and size were examined using fisheries-independent data from a long-term monitoring survey in Texas, USA. Catch, effort, and environmental covariates that affect bull shark distribution were used to create a standardized index of abundance. Increases in abundance and mean length were detected, potentially due to the initiation of federal management and restrictions on the use of gill nets in nearby Louisiana, USA, waters in 1995. This study provides a long-term perspective of two important demographic indicators (abundance and mean size) of bull shark and provides an encouraging signal in the Gulf of Mexico for a species whose stock status is unknown yet considered near threatened on the International Union for Conservation of Nature red list. Continuing research is needed to gauge effects of management and environmental impacts on shark resources as well as investigations into ecosystem effects of increasing predatory density in coastal waters.

Using long-term citizen science data to understand distribution and habitat use of an irruptive species

2021 ◽  
pp. 101377
Author(s):  
Anant Deshwal ◽  
Pooja Panwar ◽  
Joseph C. Neal ◽  
Matthew A. Young
Keyword(s):  
Habitat Use ◽  
Citizen Science ◽  
Science Data

Long-term Water Quality Trends after Implementing Best Management Practices in South Florida

2009 ◽  
Vol 38 (4) ◽  
pp. 1683-1693 ◽  
Author(s):  
Samira H. Daroub ◽  
Timothy A. Lang ◽  
Orlando A. Diaz ◽  
Sabine Grunwald
Keyword(s):  
Water Quality ◽  
Best Management Practices ◽  
Management Practices ◽  
South Florida ◽  
Best Management ◽  
Water Quality Trends

scholarly journals Stingray Habitat Use Is Dynamically Influenced by Temperature and Tides

2022 ◽  
Vol 8 ◽  
Author(s):  
Chantel Elston ◽  
Paul D. Cowley ◽  
Rainer G. von Brandis ◽  
James Lea
Keyword(s):  
Habitat Use ◽  
Acoustic Telemetry ◽  
Monsoon Season ◽  
Abiotic Factors ◽  
Environmental Drivers ◽  
Shallow Waters ◽  
Shallow Marine ◽  
Tidal Cycles ◽  
Management Plans ◽  
Passive Acoustic

Abiotic factors often have a large influence on the habitat use of animals in shallow marine environments. Specifically, tides may alter the physical and biological characteristics of an ecosystem while changes in temperature can cause ectothermic species to behaviorally thermoregulate. Understanding the contextual and relative influences of these abiotic factors is important in prioritizing management plans, particularly for vulnerable faunal groups like stingrays. Passive acoustic telemetry was used to track the movements of 60 stingrays at a remote and environmentally heterogeneous atoll in Seychelles. This was to determine if habitat use varied over daily, diel and tidal cycles and to investigate the environmental drivers behind these potential temporal patterns. Individuals were detected in the atoll year-round, but the extent of their movement and use of multiple habitats increased in the warmer NW-monsoon season. Habitat use varied over the diel cycle, but was inconsistent between individuals. Temperature was also found to influence stingray movements, with individuals preferring the deeper and more thermally stable lagoon habitat when extreme (hot or cold) temperature events were observed on the flats. Habitat use also varied over the tidal cycle with stingrays spending a higher proportion of time in the lagoon during the lowest tides, when movement on the flats were constrained due to shallow waters. The interplay of tides and temperature, and how these varied across diel and daily scales, dynamically influenced stingray habitat use consistently between three species in an offshore atoll.

scholarly journals Companions and Casual Acquaintances: The Nature of Associations Among Bull Sharks at a Shark Feeding Site in Fiji

2021 ◽  
Vol 8 ◽  
Author(s):  
Thibaut Bouveroux ◽  
Nicolas Loiseau ◽  
Adam Barnett ◽  
Natasha D. Marosi ◽  
Juerg M. Brunnschweiler
Keyword(s):  
Marine Reserve ◽  
Temporal Association ◽  
Feeding Site ◽  
Carcharhinus Leucas ◽  
Best Fitting ◽  
Social Associations ◽  
Simple Ratio ◽  
A Site ◽  
Predictor Factors

Provisioning activities in wildlife tourism often lead to short-term animal aggregations during the feeding events. However, the presence of groups does not necessarily mean that individuals interact among each other and form social networks. At the Shark Reef Marine Reserve in Fiji, several dozen bull sharks (Carcharhinus leucas) regularly visit a site, where direct feeding is conducted during tourism driven shark dives. On 3,063 shark feeding dives between 2003 and 2016, we visually confirmed the presence of 91 individual bull sharks based on external and long-lasting identification markings. We measured the intensity of associations between pairs of individuals by calculating the Simple Ratio Index (SRI) and calculated Generalized Affiliation Indices (GAIs) to distinguish true associations between dyads from structural predictor factors. Although the resulting mean SRIs were low, ranging from 0.01 to 0.12 (SRImean = 0.06; mean SRImax = 0.21), preferred long-term companionships were observed between individuals. Avoidances were also observed within pairs of individuals during the second half of the study. The best fitting model describing the temporal association patterns of bull sharks revealed a social structure which is characterized by preferred companionships and casual acquaintances. Our results suggest that the aggregation resulting from direct feeding has served to facilitate the development of social associations.

scholarly journals Evaluating deepwater fisheries management strategies using a mixed-fisheries and spatially explicit modelling framework

2013 ◽  
Vol 70 (4) ◽  
pp. 768-781 ◽  
Author(s):  
Paul Marchal ◽  
Youen Vermard
Keyword(s):  
Fisheries Management ◽  
Management Strategies ◽  
Spatially Explicit ◽  
Catch Per Unit Effort ◽  
Modelling Framework ◽  
Control Rules ◽  
Bioeconomic Modelling ◽  
Stock Assessments ◽  
Fleet Dynamics

Abstract Marchal, P., and Vermard, Y. 2013. Evaluating deepwater fisheries management strategies using a mixed-fisheries and spatially explicit modelling framework. – ICES Journal of Marine Science, 70: 768–781. We have used in this study a spatially explicit bioeconomic modelling framework to evaluate management strategies, building in both data-rich and data-limited harvest control rules (HCRs), for a mix of deepwater fleets and species, on which information is variable. The main focus was on blue ling (Molva dypterygia). For that species, both data-rich and data-limited HCRs were tested, while catch per unit effort (CPUE) was used either to tune stock assessments, or to directly trigger management action. There were only limited differences between the performances of both HCRs when blue ling biomass was initialized at the current level, but blue ling recovered more quickly with the data-rich HCR when its initial biomass was severely depleted. Both types of HCR lead, on average, to a long-term recovery of both blue ling and saithe (Pollachius virens) stocks, and some increase in overall profit. However, that improvement is not sufficient to guarantee sustainable exploitation with a high probability. Blue ling CPUE did not always adequately reflect trends in biomass, which mainly resulted from fleet dynamics, possibly in combination with density-dependence. The stock dynamics of roundnose grenadier (Coryphaenoides rupestris), black scabbardfish (Aphanopus carbo) and deepwater sharks (Centrophorus squamosus and Centroscymnus coelolepis) were little affected by the type of HCR chosen to manage blue ling.

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