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Why a California great white shark scientist opposes CA Endangered Species Act protections

csulb shark labChris Lowe -CSULBDr. Chris Lowe is a Professor of Marine Biology at California State University Long Beach, and is Director of the  CSULB Shark Lab. He has studied  California’s great white sharks for more than 10 years, and has written more than 75 peer-reviewed scientific publications. Dr. Lowe also serves on the Board of Directors for the American Elasmobranch Society, the world’s largest professional organization of shark scientists. The following guest post was also submitted as a public comment to the California Department of Fish and Wildlife.

 

Comments for consideration on the petition to list white shark as threatened or endangered species:

I am a Professor of Marine Biology and the Director of the CSULB Shark Lab at California State University Long Beach and have been conducting State and Federally permitted white shark research in California since 2002. In addition, as a professional and published shark scientist who has studied a variety of shark species around the world, including white sharks in California, I would like to take this opportunity to express my personal professional opinion in regards to the petition request and the science behind it.

The CSULB Shark Lab team prepares to work up a juvenile great white shark

The CSULB Shark Lab team prepares to work up a juvenile great white shark

For the most part, I agree with much of the CDFW’s assessment of the population status of white sharks; however, it is my professional opinion, based on the best available scientific data that the petition to list northeast Pacific white sharks as threatened or endangered is not warranted at this time. In fact, I would argue that white sharks represent an excellent example of one of California’s greatest conservation success stories.

Here are my reasons as to why:

1. Previously published population estimates for the northeastern Pacific white sharks are clearly underestimates for many of the reasons pointed out in the CDFW evaluation and there is a growing concern among many shark scientists as to the accuracy of these data. In addition, there is published evidence indicating that the northeastern Pacific white shark population has been growing over the last 10 years based on increased recruitment of young sharks in southern California and Mexico and climbing sea otter mortality due to shark bites. The likely reasons for this population increase can be attributed to:

  • -state and federal protection for white sharks significantly reducing juvenile mortality
  • -significant reductions in gillnet fishing effort since the mid 1990s significantly reducing juvenile mortality
  • -recovery of many coastal marine fish species and marine mammals as the result of vastly improved fisheries management (white shark prey base)
  • -improved water quality
  • -overall public concern for marine resources.
Figure 14.7 from Lowe et al. 2012, "Historical Fishery Interactions with White Sharks", showing that shark interactions with nets have drastically decreased since the coastal gill net restrictions in 1994 (vertical dashed line)

Figure 14.7 from Lowe et al. 2012, “Historical Fishery Interactions with White Sharks”, showing that shark interactions with nets have drastically decreased since the coastal gill net restrictions in 1994 (vertical dashed line)

It is important to note that while the arguments posed for listing are precautionary, many or all of the cited risks have already been addressed by State or Federal policies or regulations for over 15 years now (e.g., Federal Clean Water Act, Magnuson-Stevens Act, Highly Migratory Species Management Plan, Marine Mammal Protection Act, CA white shark protection legislation, CA nearshore gillnet ban, etc) and have been documented as reasons for successful recovery of numerous marine habitats and populations.

2. While there is evidence of high contaminant loads found in young white sharks, there is no evidence of any physiological impact or population-level impact. In fact, despite the high levels and known deleterious effects of these same contaminants on marine mammals they have not been shown to have had dramatic effect on pinniped populations, which have been growing at a phenomenal 6% per year over the last 15 years. Since the disposal of these contaminants has been banned for over 40 years now and environmental levels are decreasing, current contaminant loads are likely bearing even a lesser effect on marine populations that those exposed over 20 years ago.

3. While fishery interactions still occur, recent evidence suggests that the post-release survivorship of incidentally caught and released sharks is extremely high (> 95 85.7%) (Lyons et al. in prep). Furthermore, new data indicates that the potential for interaction with gillnets is much less than estimated when we examine the movement patterns of tagged and released sharks in proximity to existing fishing activities. The documented high post-release survivorship of sharks previously caught in gillnets suggests that the impact of gillnet fisheries on white shark survivorship are relatively low and can be further reduced with modifications in fishing practices such as shorter net soak times.

Although concern for adequate protection of apex predators, which naturally have relatively low population sizes is prudent, it is my professional opinion that white sharks should not be considered for listing as threatened or endangered at this time. Time and resources spent evaluating the need for listing of white sharks will reduce critical resources and effort that should be allocated to populations in greater risk. Placing species that truly do not require this level of protection only dilutes the value of this protected status listing. In addition, since I am either collaborating with or knowledgeable of all other ongoing research on white sharks in the Pacific, I can say that there will unlikely be any new findings coming out in the next year that will shed more light on this situation than already currently exists. Finally, it is important to note that the review process itself will also potentially impede our ability to gather new information needed to address data gaps due to increase permitting requirements and research restrictions.