Katie Viducic NRS 509. Shark Management

Transcription

1 Katie Viducic NRS 509 Shark Management The use of Global Information systems (GIS) and remote sensing technologies allow scientists to explore the oceans and the creatures that live there in great detail. Recent advances in satellite tagging technologies have provided scientists growing opportunities to resolve previously unknown spatial ecology of marine predators, including sharks (Hammerschlag et al 2010). Sharks are caught in marine fisheries all over the world and populations are declining due to overfishing. Many species are caught as bycatch, only a few are actually targeted. World wide there are agencies that help to manage the shark fisheries. An example here in the United States is the National Marine Fisheries Service (NMFS) Cooperative Shark Tagging Program (CSTP), whose focus is to research the biology and ecology of sharks. Tagging programs, such as the CSTP, provide data on stock structure, distribution of life history intervals, the exploitation of a resource by multinational fisheries, and direct evidence of fish movements across national and international boundaries (Kohler et al 2002). In addition, tagging studies can be designed with experimental components to estimate critical population parameters such as population size, recruitment, and mortality and survival rates (Kohler et al 2002). Satellite tagging is a valuable tool used in shark conservation and management studies, allowing scientists to remotely access these mysterious animals. In these studies different species of sharks were tagged to study their movements horizontally and vertically, migration patterns, and behaviors. It is impossible to articulate conservation needs without knowledge about mating sites, nursery grounds, and migration routes (Brunnschweiler and Van Buskirk 2006). An advantage of tagging sharks to fisheries managers is that they can highlight what waters the sharks are residing in or transiting through and can create cross-jurisdiction arrangements between countries (Holmes et al 2014). The goals of these studies were to look at the spatial and temporal dynamics of different shark populations so the scientists can draw conclusions of where these sharks are going any why. The conclusions made will inform management agencies details of various shark species and allow them to decide on fishing regulations for each species The most popular technology used in these studies are the PSAT and SPOT tags. PSAT stands for Pop- up Satellites Archival Tags. PSATs are inserted into the musculature of the shark next to the dorsal fin (Hammerschlag et al 2010). The advantage of this tag is you can deploy this in the water or from the surface and the shark doesn t need to be contained for a long period of time. PSAT tags record and store measurements of ambient light levels, swimming depth and temperature at pre-programmed intervals (Hammerschlag et al 2010). A geolocation processing software uses these observations along with corresponding reference data on sea surface temperature and bathymetry to determine an animal s locations throughout deployment (Hammerschlag et al 2010). The tags detach from the fish at a pre-programmed date and float to the surface, where they transmit summaries of their stored data to orbiting Argos satellites (Hammerschlag et al 2010). Another popular tag is the SPOT tag. SPOT stands for Smart Position Or Temperature Tag and it uses radio transmissions. To deploy the SPOT tags hole are drilled into the dorsal fin of the shark. This is more invasive than the PSAT tags and the shark needs to be contained for a longer period of time than the PSATs. The advantage of SPOT tags is obtaining near-real time tracks that provide horizontal movements that can be analyzed

2 at a much higher resolution than those from PAT tags (Hammerschlag et al 2010). When the shark s fin breaks the surface the tag transmits two or more signals to Argos Satellites above. The satellites send the information to the user and horizontal data can be turned into tracks that illustrate the data collected. Throughout these studies tracks were created and overlapped with environmental data collected from satellites such as SeaWiFS. Data collected by this satellite and compared to the tracks were sea surfaces temperature, sea surface salinity, and sea surface chlorophyll levels. When using depth data scientists were comparing features on the sea floor such as oceanic ridges to see if there are any correlations. Maps were also created to show activity zones, illustrating what the scientists believe the sharks were doing in these areas to see if any activities overlap or if different sharks are utilizing the same areas. An example of this was shown in Holland et al (1995). Hammerhead pup data was illustrated in vector and raster form. The both maps showed the overlapping in activities. The vector data was used for day and night comparison while the vector data created polygons and this was considered an example of foraging behavior. Foraging behavior is seen when the sharks are circling or turning through previous paths showing that they are in search of something. This was demonstrated in the day verse night behavior. Pups were tracked as going in straight lines rather than circular and swimming speeds increased. There wasn t an explanation for this data at this time but I would think the increased speed was to avoid predators and maybe the direct line was to get to an area of shelter. Though it seems that there is a lot of tagging data out there it is still limited in relation to the number of sharks out there. Technology is growing daily and new information is being created. In Bonfil et al (2005) it was thought that female great white sharks do not make transoceanic migrations but this data showed otherwise. This is not necessarily true for all female white sharks. This study focused on the populations off the coast of Australia and perhaps in other populations off the coast of California it is true that females do not make that journey. Different populations have different behaviors. Their biology might be the same but there are environmental factors that influence sharks all over the word. Therefore management decisions will vary by species and by location. In Holmes et al (2014) the scientists looked at the temporal movements of tiger sharks off the coast of Australia. Periods of tiger shark residency outside of Australia s fisheries management zones highlight the potential vulnerability of the species to unregulated fisheries and the importance of crossjurisdictional arrangements for species management and conservation (Holmes et al 2014). Though Australia s population of tiger sharks are at sustainable numbers the data founded by them and other scientists show that sharks make these transatlantic movements; which need to be considered in international conservation. With rising prices and demand in the international shark fin trade, together with the lack of high-seas fisheries management, these catches are likely to increase in the future (Stevens et al 2010). There is increasing concern over the status of pelagic shark populations and an urgent requirement for better catch data collection and information on their biology and behavior to aid management and ensure sustainable use of these resources (Stevens et al 2010). Overall, without GIS and remote sensing technologies none of this information would have been possible. Satellites such as Argos and SeaWiFS provide information that is crucial to studying the ocean and the animals that inhibit it. All of these studies have provided new information on multiple species of sharks. These data will assist in assessing the vulnerability of

3 pelagic sharks (Stevens et al 2010). Long-term shark tracks achieved through improved tag - attachment methods and tag technology (Stevens et al 2010) will only get better in the future and will create a bigger picture of where sharks are going and why. Bibliography: Bonfil, R., Meyer, M., Scholl, M.C., Johnson, R., O'Brien, S., Oosthuizen, H., Swanson, S., Kotze, D., Paterson, M., Transoceanic migration, spatial dynamics, and population linkages of white sharks. Science 310 (5745), In the study by Bonfil et al (2005) satellite tagging and photo identification was used to study the migration and behavioral patterns of white sharks. The transoceanic migrations gave evidence to link the populations of white sharks in Africa and Australia. The data collected showed that sharks returned to original tagging locations and disproved suggestions that female white sharks do not make transatlantic migrations. Data collected included percent of time spent at depth in costal and transatlantic regions, temperature at depth, and locations were plotted against average sea surface temperatures. The authors found that this population of sharks dove to 980 meters. They also found that the sharks were able to tolerate temperatures as low as 3.4 degrees Celsius. This study worked to understand connections between different populations with in a shark species. These transatlantic migrations provide information to managers on what waters these sharks are entering and provide information so managers around the world can work together to sustainably manage this species. Brunnschweiler, J.M., Van Buskirk, J., Satellite tagging of bull sharks at Walker's Cay in the Bahamas. Bahamas Nat. J. Sci. 1, This study by Brunnschweiler et al (2006) provided data on habitat use and movements of bull sharks tagged in the Bahamas. The sharks were tagged with pop-up tags that recorded the location, depth preferences, and temperature preferences. This study collected data that confirmed the movements of bull sharks between the Bahamas and Florida. This shows that international cooperation is needed for conservation and management of this bull shark population. The seasonal locations need to be further studied so that managers can create appropriate management planning. Studies such as this are limited in the number of individuals tagged due to cost but provide vital information. If more studies like this one are performed sustainable bull shark populations will exist. Overall, this paper was well written and executed and I am looking forward to reading further studies by these authors. Hammerschlag, N., Gallagher, A.J. & Lazarre, D.M. (2011) A review of shark satellite tagging studies. Journal of Experimental Marine Biology and Ecology, 398, 1 8. In this paper by Hammerschlag et al (2011) the authors reviewed satellite tagging studies performed between 1984 and This study analyzed the use of satellite tagging for studying the behavior and ecology of different shark species preformed by different scientists. The authors of this study focused on the tagging locations, species studied, technology used and how it was deployed, sample size, duration of study, and other study limitations. The different technologies used are compared for efficiency and physiological and behavioral affects are discussed. The different tags used have different capabilities. The tags are able to record temperature, light levels, depths, and chlorophyll levels. And more technologies are being

4 created for near future use. The data we are able to receive is limited currently but with growing technology I am excited to see the level of detail we are going to be able to achieve. This paper was able to give a great comparison of the different technologies and methods being used in todays studies on shark tracking. Holland. K.N.. Wetherbee, B.M., Peterson, J.D. and Lowe, C.G, Movements and distribution of Hammerhead shark pups on their natal grounds. Copeia, This study by Holland et al (1993) showed at different method of tagging compared to other papers I have read. Because the dorsal fin of a pup is so small it cannot support the weight of a SPOT tag. The PSAT is also not an option for pups because it would create too much drag and not allow the pups to swim properly. Therefore the scientists used ultrasonic transmitters, which were force fed to the sharks and laid in their stomach. Movements where tracked in hope of seeing where these pups are residing to hide from predators and to feed on smaller fish. Knowing potential habitats could help in management decisions of where fishermen are allowed to fish in order to avoid these pups. These scientists used vector data to show the tracks of the horizontal movements and also used raster data to show the differences in day verse nighttime movements. I thought this was very interesting, as I haven t seen someone use raster data to illustrate movements before. The speed of the pups was also found which was interesting to myself and the other authors as the speeds reach were greater than previously thought. Holmes, B. J. et al. Tiger shark (Galeocerdo cuvier) movement patterns and habitat use determined by satellite tagging in eastern Australian waters Mar. Biol. 161, In the study by Holmes et al (2014) tiger sharks were tagged to study their movements off the coast of Australia. SPOT and pop-up tags were used to record horizontal and vertical migrations. Data found in this study included time at depth, temperature, and location. Tiger sharks were found to spend most of their time at depths less than 20 meters but dove to depths up to 920 meters. The average surface temperature where this tiger shark population was found was 29.5 degrees Celsius and were able to inhabit temperatures of 5 degrees Celsius. This study was able to track sharks up to 408 days which is very successful for shark tagging studies. This study looked at temporal factors and characterized resident and transit movement patterns. This study is essential for management efforts of tiger sharks. Tiger sharks are unmanaged in Australia and hopefully this paper can bring insight to managers to start regulating tiger shark fishing. Kohler, N. E., Turner, P. A., Hoey, J. J., Natanson, L. J., and Briggs, R. (2002). Tag and recapture data for three pelagic shark species, blue shark (Prionace glauca), shortfin mako (Isurus oxyrinchus), and porbeagle (Lamna nasus) in the North Atlantic Ocean. International Commission for the Conservation of Atlantic Tunas, Collective Volume of Scientific Papers SCRS/2001/64 54, In this study by Kohler et al (2002) the tag and recapture information for the blue shark, short fin mako shark, and porbeagle from 1962 to 2000 was summarized. The National Marine Fisheries Service (NMFS) Cooperative Shark Tagging Program (CSTP) was created in 1962 and relies on the tag and recapture of tagged sharks by scientists and volunteers. This method is cost effective but does not provide the detailed information that satellite tags provide. However unlike satellite studies were cost effects the sample size, this method has successfully tagged 243,000 sharks of fifty-two species but has only recaptured 14,000 of 33 species. This method still provides vital data on shark populations and spatial dynamics. This study provided details on

5 sex ratios and information on where different age groups and states of maturity are located. This study provides a lot of data that satellite-tagging studies would not have been able to provide. This study was written by a group of prestigious scientists in this field and was provided excellent data. Stevens, J.D., Bradford, R.W., West, G.J., Satellite tagging of blue sharks (Prionace glauca) and other pelagic sharks off eastern Australia: depth behavior, temperature experience and movements. Mar. Biol. 157 (3), In the study by Stevens et al (2010) scientists satellite tag multiple species of sharks comparing their diel and horizontal movements. The study compared the amount of time the sharks spent at depth or at the surface and recorded the temperatures where the sharks were inhibiting. Commercial and recreational fisheries target all the species of sharks in this study however they are also caught as bycatch. This study brings up the concern of declining populations due to the finning trade and how more studies like this one need to be conducted so that fisheries management agencies are able to assess populations and learn more about these species. The study analyzed tag performance so that future studies can use the best performing tags to collect accurate data. The spatial data was overlapped with data collected by MODIS and SeaWiFS to determine what features were attracting sharks to these locations. One shark seemed to have followed an oceanic ridge but no other sharks seemed to orient to a specific feature. Mean chlorophyll levels and sea surface temperature were also calculated and no obvious correlations were found. I believe if more data is collected and individual species are studied correlations between these factors will reveal patterns.