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The Foundation supports projects both financially and in an advisory function. For purposes of controlling results and ensuring quality it requests yearly project reports. Whenever necessary, Shark Foundation projects are examined by the Foundation's > scientific advisory committee which is composed of highly qualified shark researchers and scientists.

We need your help in order to carry out the various projects. You can support individual projects directly by noting the respective donation code on the > deposit slip or > bank transfer.


 Nurse shark thermoregulation

Donation code: Nurse shark thermoregulation

CEFAS tag on female nurse shark #286
© Wes Pratt
CEFAS tag on female nurse shark #286

Behavioral thermoregulation after mating by female nurse sharks

For thousands of years, adult nurse sharks (> Ginglymostoma cirratum) have most likely been returning to the > Dry Tortugas shallows to court and mate in June and July. Using kayaks and simple nets, our research team has tagged, released and studied over 100 female nurse sharks during the past 21 years.

Sharks chose specific habitat for various reasons at different times of their lives. The relevance of this project is to understand the requirements for reproductive success in shark populations by elucidating the need of pregnant females for specific temperature regimes. Temperature is one of the most critical factors determining the distribution and success of animal populations. Female nurse sharks mate in shallow lagoons in June and July. Some of these females return to the same lagoons in autumn to bask in the warm shallow waters. It is our hypothesis that they seek out these waters to warm their bodies, much as reptiles do, to facilitate gestation and an early parturition.


Tagged nurse shark in the shallow warm waters of the Dry Tortugas.
© Wes Pratt
Tagged nurse shark in the shallow warm waters of the Dry Tortugas.

With the help of Hai-Stiftung, we purchased 14 CEFAS G5 temperature/depth recording tags to place on adult female nurse sharks. As our sharks return to the Dry Tortugas mating site bi- and triennially, it was decided to deploy half the tags in 2011 and the other half in 2012.

Activities in 2012
In 2012, 13 adult females and seven adult males were captured or recaptured. Eight of these females were net captured and tagged or retagged, three were observed photographically and two electronically. The seven males were 'recaptured' electronically or visually/photographically. Eight of the females were fitted with CEFAS G5 temperature/depth loggers. This year our research team spent 28 days on-site. We conducted around 140 hours of observation. 137 shark courtship and mating events which is comparable to other years.

Results until June 2012
To date, 145 adult sharks have been tagged. Forty-seven of these adults have been recaptured a total of 117 times (range 1 to 6 recaptures) in the breeding and refuging grounds where they were tagged. As noted, our sharks only mate once a year. They have not been available to capture and tag since our last reporting period in June of 2011.

Future plans
In 2013 we will make our 23rd annual trip to the Dry Tortugas shark mating site to deploy another group of CEFAS G5 tags and to download the fixed loggers. The group we tagged in 2012 will be expected to return in 2014.


Project leader: Wes Pratt

The Foundation finances this project since 2011.
Investments to date: CHF 7'500.00


 
 Diet of juvenile lemon sharks

Donation code: Diet of juvenile lemon sharks

Juvenile lemon sharks diet

Feeding is an essential process to sustain an organism's life by supporting the body with the energy that is used for survival, fitness, growth and reproduction. In many marine ecosystems, sharks act as top predators The anthropogenic removal of food and habitat resources from marine ecosystems may affect the sharks that rely upon them.

The island Bimini is a habitat for a wide range of coastal species and serves as a nursery ground for juvenile lemon sharks (Negaprion brevirostris). Juvenile lemon sharks (0 - 4 years) use the mangrove fringed habitat as a protective shelter from large coastal predators but also as a forage ground. In the last ten years the construction work of a mega resort destroyed a large amount of the mangrove fringed shoreline and the adjacent seagrass patches. In order to investigate the possible anthropogenic influence on the prevalent ecosystem, we sampled, identified and measured prey species over a period of six months. We identified the stomach contents of juvenile lemon sharks and compared the results to a pre-development data set (2000 - 2003).


Bimini lemon shark  nursery.
© Ornella Weideli
Bimini lemon shark nursery.

We hypothesized that this habitat destruction will result in an alteration of the prey community leading to a dietary shift in the highly site-attached juvenile lemon sharks. However, no such shift in the prey community was found. The five major prey families were found in unchanged proportions between the two sampling periods. On the contrary, the diet of juvenile lemon sharks was significantly changed independently from the prey community. Not only did the major five prey families found in stomachs change, but also novel prey species were found in stomachs. For example: non-resident pelagic fish species, remaining of queen conchs and chicken bones .


Stomach content analysis
© Ornella Weideli
Stomach content analysis

The identification of these food items lead to the hypothesis that juvenile lemon sharks are scavenging food. We assumed that scavenging food, in addition to a regular foraging behaviour, could be beneficial in an anthropogenic altered habitat, because it means minimal energy expenditure for juvenile lemon sharks. But further studies investigating potential dietary shifts have to be developed to fully resolve the influence anthropogenic habitat destruction might have on juvenile shark species.


Project leader: Ornella Weideli

The Foundation finances this Master thesis of the University Basel with CHF 4'000.00

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