scholarly journals Hunting tactics of the lemon shark, Negaprion brevirostris, in shallow waters of an oceanic insular area in the western equatorial Atlantic

2017 ◽  
Vol 15 (1) ◽  
Author(s):  
Ricardo C. Garla ◽  
Otto B. F. Gadig ◽  
José Garcia Junior ◽  
Leonardo B. Veras ◽  
Domingos Garrone-Neto
Keyword(s):  
Surf Zone ◽  
Sandy Beaches ◽  
Shallow Waters ◽  
Equatorial Atlantic ◽  
Lemon Shark ◽  
Negaprion Brevirostris ◽  
Total Length ◽  
Lemon Sharks ◽  
Fernando De Noronha ◽  
Hunting Tactics

ABSTRACT The hunting tactics of lemon sharks, Negaprion brevirostris, are described from underwater and cliff-top observations in the Fernando de Noronha Archipelago, western equatorial Atlantic, Brazil. Two main tactics were observed in the shallow waters of sandy beaches and reefs environments: (i) “substrate inspection” of crevices and holes over rocky and reef bottoms, and (ii) “sardine blitz”, which refer to striking schools of fishes (mainly sardines) in the surf zone. The first tactic was restricted to juveniles up to 2 m of total length, whereas subadult and adult sharks with total length larger than 2 m displayed the second. As lemon sharks use waters less than 5 m depth to hunt, perform social behaviours and predator avoidance, results highlight the importance of properly managing these habitats for their conservation, especially in areas where tourism has increased substantially.

scholarly journals Nursery area and size structure of the lemon shark population, Negaprion brevirostris (Poey, 1868), in Los Roques Archipelago National Park, Venezuela

2016 ◽  
Vol 21 (1) ◽  
pp. 33 ◽  
Author(s):  
Rafael Tavares ◽  
Jon Paul Rodriguez ◽  
Misael Morales
Keyword(s):  
Management Strategy ◽  
Size Structure ◽  
Size Composition ◽  
Nursery Area ◽  
Lemon Shark ◽  
Ecological Benefits ◽  
Time Activity ◽  
Negaprion Brevirostris ◽  
Lemon Sharks ◽  
Different Sources

The protection of the habitats used by juvenile sharks is a management strategy that has recently caught the attention of fishery biologists. In the present study, we evaluated the population of the lemon shark (<em>Negaprion brevirostris</em>) from Los Roques Archipelago in order to identify the nursery area, describe the size composition, and examine the variation in nocturnal activity of the juvenile individuals. The data analysed came from three different sources: commercial shark fishery, tag-recapture sampling, and visual records. A total of 375 lemon sharks with total lengths between 55 and 281 cm were recorded during the study period. Overall data showed that the area occupied by juvenile lemon sharks was clearly partitioned into primary and secondary nurseries. Additionally, nighttime activity seemed to change according to the size of sharks in the primary nursery, suggesting a reduction of time activity overlapping among juveniles of distinct size/age. Results suggest that the strategy of utilization of the primary nurseries by the lemon shark may lead to important ecological benefits by reducing the competition, predation and natural mortality.

scholarly journals Distribution and length composition of lemon sharks (Negaprion brevirostris) in a nursery ground in southern Cuba

2020 ◽  
Vol 103 (12) ◽  
pp. 1583-1594
Author(s):  
Alexei Ruiz-Abierno ◽  
J. Fernando Márquez-Farías ◽  
Robert E. Hueter ◽  
Lázaro Macías-Romero ◽  
J. Manuel Barros-García ◽  
...  
Keyword(s):  
Size Range ◽  
Nursery Area ◽  
Nursery Ground ◽  
Lemon Shark ◽  
Negaprion Brevirostris ◽  
Wildlife Refuge ◽  
Sandy Substrate ◽  
Lemon Sharks ◽  
Mean Size ◽  
User Groups

AbstractCharacterization of essential habitat for sharks is a key requirement for effective conservation of shark populations. In Cuba, shark essential habitat is largely undocumented. Here we present the first study of a shark nursery area in Cuban waters, for the lemon shark. Nursery areas for lemon sharks are typically surrounded by mangroves and contain sandy substrate where the young can feed, grow, move, and eventually disperse from the area. We conducted our study in Cuba’s La Salina Wildlife Refuge during 2015–2019, to understand the role this refuge might play as a lemon shark nursery area, by documenting the distribution and length structure of juveniles. Our results indicate that juvenile lemon sharks are present throughout much of the refuge with no clear pattern of aggregation by size. The size range of all juveniles captured was 39.8–108.0 cm precaudal length (PCL) with a mode in length-class 70.0–75.0 cm PCL. The mean size and weight of all individuals during the study period was 75.8 cm PCL and 5.5 kg, respectively. We infrequently observed neonates in May, June, and September with size range 39.8–55.5 cm PCL. Enforcement of management regulations, difficult access to the refuge for fishers and other user groups, and isolation from human settlements are factors that help maintain nearly pristine conditions in La Salina Wildlife Refuge. The size/age structure of lemon sharks likely represents a population unaltered by human influence. We recommend our study be expanded to contribute to shark conservation and management as outlined in Cuba’s National Plan of Action for sharks.

scholarly journals Modeling the population dynamics of lemon sharks

2014 ◽  
Author(s):  
Easton R White ◽  
John D Nagy ◽  
Samuel H Gruber
Keyword(s):  
Time Series ◽  
Population Dynamics ◽  
Age Structure ◽  
Population Fluctuations ◽  
Lemon Shark ◽  
Demographic Stochasticity ◽  
Negaprion Brevirostris ◽  
Lemon Sharks ◽  
Long Time ◽  
Structure Density

Long-lived marine megavertebrates (e.g. sharks, turtles, mammals, and seabirds) are inherently vulnerable to anthropogenic mortality. Although some mathematical models have been applied successfully to manage these animals, more detailed treatments are often needed to assess potential drivers of population dynamics. In particular, factors such as age-structure, density-dependent feedbacks on reproduction, and demographic stochasticity are important for understanding population trends, but are often difficult to assess. Lemon sharks (Negaprion brevirostris) have a pelagic adult phase that makes them logistically difficult to study. However, juveniles use coastal nursery areas where their densities can be high. Thus, we use a stage-structured, Markov-chain stochastic model to describe lemon shark population dynamics from a 17-year longitudinal dataset at a coastal nursery area at Bimini, Bahamas. We found that the interaction between delayed breeding and demographic stochasticity accounts for 33 to 49% of the variance. Demographic stochasticity contributed all random effects in this model, suggesting that the existence of unmodeled environmental factors may be driving the majority of interannual population fluctuations. In addition, we are able to use our model to estimate the natural mortality rate of older age classes of lemon sharks that are difficult to study. Further, we use our model to examine what effect the length of a time series plays on deciphering ecological patterns. We find that — even with a relatively long time series — our sampling still misses important rare events. Our approach can be used more broadly to infer population dynamics of other large vertebrates in which age structure and demographic stochasticity are important.

scholarly journals Modeling the population dynamics of lemon sharks

2014 ◽  
Author(s):  
Easton R White ◽  
John D Nagy ◽  
Samuel H Gruber
Keyword(s):  
Time Series ◽  
Population Dynamics ◽  
Age Structure ◽  
Population Fluctuations ◽  
Lemon Shark ◽  
Demographic Stochasticity ◽  
Negaprion Brevirostris ◽  
Lemon Sharks ◽  
Long Time ◽  
Structure Density

Long-lived marine megavertebrates (e.g. sharks, turtles, mammals, and seabirds) are inherently vulnerable to anthropogenic mortality. Although some mathematical models have been applied successfully to manage these animals, more detailed treatments are often needed to assess potential drivers of population dynamics. In particular, factors such as age-structure, density-dependent feedbacks on reproduction, and demographic stochasticity are important for understanding population trends, but are often difficult to assess. Lemon sharks (Negaprion brevirostris) have a pelagic adult phase that makes them logistically difficult to study. However, juveniles use coastal nursery areas where their densities can be high. Thus, we use a stage-structured, Markov-chain stochastic model to describe lemon shark population dynamics from a 17-year longitudinal dataset at a coastal nursery area at Bimini, Bahamas. We found that the interaction between delayed breeding and demographic stochasticity accounts for 33 to 49% of the variance. Demographic stochasticity contributed all random effects in this model, suggesting that the existence of unmodeled environmental factors may be driving the majority of interannual population fluctuations. In addition, we are able to use our model to estimate the natural mortality rate of older age classes of lemon sharks that are difficult to study. Further, we use our model to examine what effect the length of a time series plays on deciphering ecological patterns. We find that — even with a relatively long time series — our sampling still misses important rare events. Our approach can be used more broadly to infer population dynamics of other large vertebrates in which age structure and demographic stochasticity are important.

scholarly journals Emergence and Migration of a Nearshore Bar: Sediment Flux and Morphological Change on a Multi-Barred Beach in the Great Lakes

2007 ◽  
Vol 60 (1) ◽  
pp. 31-47 ◽  
Author(s):  
Brian Greenwood ◽  
Allana Permanand-Schwartz ◽  
Christopher A. Houser
Keyword(s):  
Great Lakes ◽  
Suspended Sediment ◽  
Surf Zone ◽  
Sandy Beaches ◽  
Sediment Flux ◽  
Accommodation Space ◽  
Longshore Transport ◽  
Sediment Balance ◽  
And Migration ◽  
Equilibrium Morphology

Abstract Burley Beach (southeastern Lake Huron) exhibits a multi-barred shoreface, the long-term equilibrium morphology characteristic of many low angle, sandy beaches in the Canadian Great Lakes. During a single major storm, a new bar emerged 50-60 m offshore as an irregular trough-crest form, through differential erosion of an existing shore terrace. Emergence, bar growth and offshore migration were associated with: (a) an overall negative sediment balance in the inner surf zone initially (‑2.30 m3>/m beach width), but with a large positive sediment balance (+5.10 m3/m) subsequent to the storm peak and during the storm decay; (b) progradation of the beach step to produce a new shore terrace; and (c) offshore migration of the two outer bars to provide the accommodation space necessary for the new bar. The primary transport mechanisms accounting for emergence of the new bar, its growth and migration were: (a) the mean cross-shore currents (undertow), which always transported suspended sediment offshore; and (b) the onshore transport of suspended sediment by incident gravity wave frequencies early in the storm and subsequently by infragravity waves (at the storm peak and the decay period). The longshore transport of sediment was significant in terms of the gross transport, although the net result was only a small transport to the south-west (historic littoral transport direction). It did not cause bar initiation, but it may have supplied some of the sediment for bar growth. The primary mechanism for bar initiation and growth was the cross-shore displacement of sediment by wave-driven (oscillatory) transport and cross-shore mean currents (undertow).

Homing ability of young lemon sharks, Negaprion brevirostris

2005 ◽  
Vol 72 (3) ◽  
pp. 267-281 ◽  
Author(s):  
Susi Manuela Clermont Edr�n ◽  
Samuel H. Gruber
Keyword(s):  
Negaprion Brevirostris ◽  
Lemon Sharks

scholarly journals MASSIVE USE OF BERM RELOCATION AND SURFWASHING DURING THE 2006 JYEH OIL SPILL (LEBANON): THE ACCURATE RESPONSE FOR BEACHES CLEANUP

2008 ◽  
Vol 2008 (1) ◽  
pp. 331-338 ◽  
Author(s):  
Bernard Fichaut ◽  
Bahr Loubnan
Keyword(s):  
Surf Zone ◽  
Weather Conditions ◽  
Fuel Oil ◽  
Shallow Waters ◽  
Power Station ◽  
Heavy Fuel Oil ◽  
Sediment Removal ◽  
Calm Weather ◽  
Oily Waste

ABSTRACT Following the bombardment of the Jyeh power station in Lebanon on July 16 2006, about 10 to 15000 tons of heavy fuel oil drifted 150 km northward all the way to the Syrian border. Because of the continuing war, the cleanup operations could not start until early September. The response consisted of conceptually dividing the coast line into several sectors managed by various operators; from Jyeh to Beyrouth, a 34.5 km stretch of shoreline, the treatment of beaches was assigned to the lebanese N.G.O “Bahr Loubnan’. In this area, 5.3 km of sandy and gravel beaches appeared to be heavily oiled on a width that seldomly exceeded 10 m. Oil was found buried down to a depth of 1.8 m at several locations. Additionnally oil was also found sunken in shallow waters in the breaker zones of numerous beaches. In order to minimize sediment removal and production of oily waste to be treated, it was decided to operate massive treatmenN in situ. After manual recovery of stranded oil, about 12,000 m of sediment including 1,000 m of cobbles have been relocated in the surf zone. Despite the lack of tides and of the generally calm weather conditions, surfwashing was very efficient due mainly to the fact that, in non tidal conditions, sediments are continuously reworked by wave açtion which operates at the same level on the beaches. Only 540 m of heavily oiled sand, was removed from beaches and submitted for further treatment. The lack of appropriate sorbents material in Lebanon to capture the floating oil released by surfwahing was also a challenge. This was addressed by using locally Nmanufactured sorbents, which proved to be very efficient and 60 m of sorbent soaked with oil were produced during the cleanup.

Behavioral modification of visually deprived lemon sharks (Negaprion brevirostris) towards magnetic fields

2014 ◽  
Vol 453 ◽  
pp. 131-137 ◽  
Author(s):  
C.P. O'Connell ◽  
T.L. Guttridge ◽  
S.H. Gruber ◽  
J. Brooks ◽  
J.S. Finger ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Behavioral Modification ◽  
Negaprion Brevirostris ◽  
Lemon Sharks
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