My last post presented a pretty bleak view of current shark populations and the challenges they face, so this week I want to focus on the ways that researchers are trying to understand the most important aspects of shark conservation- sometimes the strategies they propose aren’t effective, but still lead to improved shark knowledge and protection.
Great Hammerhead Shark
One option is to protect the areas which are important to specific populations that are in trouble. Nursery areas, for example, have been suggested as great targets for conservation (Heupel et al. 2007)- although definitions for what a nursery is are still evolving, the general idea here is places where females give birth or lay eggs, or places where juveniles grow toward maturity. It is possible that these areas have high food density or low predator density (remember that little sharks are eaten by bigger sharks), or it could be that the warmers water usually associated with nursery areas allows sharks to grow more quickly. We do have to be careful, however, about focusing too much on nursery areas alone- when school shark nursery areas were protected in Australia, but harvesting of adults continued, populations still declined because the juveniles weren’t growing quickly enough to reach breeding maturity and replace the lost adults (Kinney & Simpfendorfer 2009). Certain areas of the world seem more important for shark conservation than others. Coastal sharks are particularly at risk because of proximity to human activity (Speed et al. 2010), and Pacific coastal sharks at the mid-latitudes (read: around southern Japan and Australia) show the highest species richness of sharks anywhere, making these areas very important for conservation of shark biodiversity (Lucifora et al. 2011). Time of year and even time of day make things even more complicated. Most species of shark are known to show some type of migratory pattern- recent research in South Africa, for example, showed that although male and female great whites were found together feeding on seals in the winter, during spring and summer months females stayed in inshore areas while males dispersed (Kock et al. 2013). Whale shark numbers off the coast of India increase during the pre-monsoon period and then the animals seem to leave the coast during the monsoon (Pravin 2000). Some shark species are more active at night, as with the blue shark in the eastern Atlantic- GPS tracking of these animals revealed that they had daily depth migration patterns, and night-time foraging in highly productive waters was concentrated in the top 100m of water, essentially the same depths targeted by long-lines fishing for swordfish and tuna, putting the sharks at risk (Queiroz et al. 2012).
Better-regulated and -ENFORCED international regulations have also been called for. Scientists studying shark populations off the coast of Italy have suggested that efforts to protect shark species there are hampered by lack of information on exactly which shark species are being caught (Dell’Apa et al. 2012), and I found that was a regular refrain, from IUCN reports (Camhi et al. 2009) to discussion of harvest numbers from Chile (Sebastian et al. 2008). Genetic tests can help keep track of species numbers, and several countries including the US have passed regulations requiring that fins must remain attached to sharks that are landed to reduce the practice of finning sharks and leaving them in the ocean to die and promote use of all parts of landed sharks (Techera 2012). One of the big issues with regard to shark conservation is enforcing regulations and developing international cooperation. Many international plans for shark protection provide guidelines for shark protection but lack the power to generate consequences for groups that ignore the guidelines (Techera & Klein 2011); since sharks are such mobile animals, this means that the efforts of one country with strong domestic protections can be totally undone by a neighbor without the same commitment. Some researchers have suggested that focusing on the difference in economic value between living and dead sharks may be one way to generate support for shark protection- it was estimated that a living shark which helped attract shark tourism to Palau was worth $1.9 million over its lifetime, versus $114 as a harvested animal (Techera 2012).
And these efforts are having an impact, albeit slowly. White shark numbers around Australia have increased as a result of protection (Ward-Paige et al. 2012); as a result of gillnet bans in the eastern Pacific, school shark numbers are up as well. Changes in fishery practices have also helped diamond and brown ray populations around South Africa and little and rosette skate populations in the northwest Atlantic. Several nations have created shark sanctuaries out of their territorial waters, including Palau, the Bamahas, Honduras, and the Maldives (Techera 2012).
So researchers are doing their best to understand what makes shark conservation effective, and groups around the world are working to create movements and legislation to make shark protection widespread- I have no doubt that researchers and activists could use our help in their efforts. In my final post for the month, I’ll provide ways that you can directly impact shark conservation without even going in the water (unless you want to…).
Works cited:
Camhi, MD, Valenti, SV, Fordham, SV, Fowler, SL, and C Gibson. 2009. The Conservation Status of Pelagic Sharks and Rays: Report of the IUCN Shark Specialist Group Pelagic Shark Red List Workshop. IUCN Species Survival Commission Shark Specialist Group. Newbury, UK.
Dell’Apa, A, Kimmel, DG and S Clo. 2012. Trends of fish and elasmobranch landings in Italy: associated management implications. ICES Journal of Marine Science 69: 1045-1052.
Heupel, MR, Carlson, JK, and CA Simpfendorfer. 2007. Shark nursery areas: concepts, definition, characterization and assumptions. Marine Ecology Progress Series 337: 287-297.
Kinney, MJ and CA Simpfendorfer. 2009. Reassessing the value of nursery areas to shark conservation and management. Conservation Letters 2: 53-60.
Kock, A, O’Riain, MJ, Mauff, K, Meyer, M, Kotze, D, and C Griffiths. 2013. Residency, habitat use and sexual segregation of white sharks, Carcharodon carcharias in False Bay, South Africa. PLoS ONE 8: e55048.
Lucifora, LO, Garcia, VB and B Worm. 2011. Global diversity hotspots and conservation priorities for sharks. PLoS ONE 6: e19356.
Pravin, P. 2000. Whale shark in the Indian coast- need for conservation. Current Science 79: 310-315.
Queiroz, N, Humphries, NE, Noble, LR, Santos, AM and DW Sims. 2012. Spatial dynamics and expanded vertical niche of blue sharks in oceanographic fronts reveal habitat targets for conservation. PLoS ONE 7: e32374.
Sebastian, H, Haye, PA and MS Shivji. 2008. Characterization of the pelagic shark-fin trade in north-central Chile by genetic identification and trader surveys. Journal of Fish Biology 73: 2293-2304.
Speed, CW, Field, IC, Meekan, MG and CJA Bradshaw. 2010. Complexities of coastal shark movements and their implications for management. Marine Ecology Progress Series 408: 275-293.
Techera, EJ. 2012. Fishing, finning and tourism: trends in Pacific shark conservation and management. The International Journal of Marine and Coastal Law 27: 597-621.
Techera, EJ and N Klein. 2011. Fragmented governance: reconciling legal strategies for shark conservation and management. Marine Policy 35: 73-78.
Ward-Paige, CA, Keith, DM, Worm, B and HK Lotze. 2012. Recovery potential and conservation options for elasmobranchs. Journal of Fish Biology 80: 1844-1869.