By: Dana Sackett
Hurricanes can devastate a coastline for all who reside there, people and fish alike (see previous articles by The Fisheries Blog, which detail these impacts here and here). Despite the devastation that hurricanes can leave in their wake, there are some species that, surprisingly enough, flourish as a result of these massive storms. For instance, one group of researcher noted that Hurricane Katrina indirectly resulted in a dolphin baby boom. The reason for this lies with the destruction of a significant portion of commercial fishing vessels and a large portion of dolphin calves that perished during the storm (seems counter intuitive but read more below to find out why).
Hurricane Katrina destroyed 87% of commercial fishing vessels, resulting in a large drop in the amount of seafood harvested in the Gulf of Mexico in the years following Katrina. Thus, in a way, the hurricane indirectly created an undesignated and temporary marine reserve in the Gulf of Mexico. As a result, several previously harvested fish populations were left to grow larger and more abundant, as were their predators. Dolphins in particular were better able to deliver and nurse healthy baby dolphins as a result of the abundance of prey resources; allowing more of the babies to survive infancy.
In addition, adult female dolphins often become fertile within the year following the loss of a calf. This means that if a large number of calves are lost during a storm, which was seen in the study, that there would be a large number of reproductively active females in the next breeding season. Consequently, the large number of reproductive females and abundant food resources resulted in the dolphin baby boom observed by researchers two years following Hurricane Katrina.
In 1995, Hurricanes Erin and Opal also demonstrated that some fish can benefit from these storms through the movement of their habitat. These hurricanes displaced a number of artificial reef structures used by red snapper, gag grouper and gray triggerfish in the Gulf of Mexico. The relocated structures were still utilized by the fish following the hurricanes but the new locations were unknown to fishers. Researchers estimated that fishing pressure was reduced at these structures for approximately a year following the storm; resulting in the fish at these structures growing larger and more abundant. Results of this nature also indicate that some storms may have a less damaging impact on a fish population and its connected ecosystem than overfishing.
As an environmental toxicologist, chemicals and pollutants are always at the forefront of my thoughts and another often overlooked consequence of hurricanes. In this instance, while the indirect positive impact of a few rebounding fish populations following a storm seems good, I have concerns about the environment that these populations are thriving-in. Hurricanes have been associated with increases in contaminant levels in water and sediment because high winds and flooding can cause long-buried pollutants, surface pollutants, and pollutants from destroyed buildings to be liberated into the environment. For example, in the Gulf of Mexico, one study estimated that Hurricanes Katrina and Rita redistributed near 5 times the annual mercury input from the Mississippi-Atchafalaya River system and the atmosphere. Thus, I worry that the small positive impacts on the few aquatic populations indirectly benefiting from these storms may be hindered or short-lived by the exposure-to and accumulation-of these contaminants.
References and other reading material:
Burkholder J, Eggleston D,Glasgow H, Brownie C, Reed R, Janowitz G et al. 2004. Comparative impacts of two major hurricane seasons on the Neuse River and western Pamlico Sound ecosystems. PNAS 101:9291-9296.
Goldman JG. 2017. Hurricanes: Bad for People, Good for Dolphins. Katrina led to a marine-mammal boom, and Harvey, Irma and Jose might do the same. Scientific American.
Johnson WE, Kimbrough KL,Lauenstein GG, Christensen J. 2009. Chemical contamination assessment of Gulfof Mexico oysters in response to hurricanes Katrina and Rita. Environ Monit Assess 150:211-225.
Liu B, Schaider LA, Mason RP, Bank MS, Rabalais NN,Swarzenski PW, Shine JP, Hollweg T, Senn DB. 2009. Disturbance impacts on mercury dynamics in northern Gulf of Mexico sediments. Journal of Geophysical Research 114: G00C07,doi:10.1029/2008JG000752
Maslova L. 2017. Water quality responses from major hurricanes in Robeson County: a review and historic data analysis. North Carolina State University MS Thesis in Environmental Assessment.
Miller LJ, Mackey AD, Hoffland T, Kuczaj SA. 2010. Potential effects of a major hurricane on Atlantic bottlenose dolphin (Tursiops truncates) reproduction in the Mississippi Sound. Marine Mammal Science 26:707-715.
Turpin RK, Bortone SA. 2002. Pre- and post-hurricane assessment of artificial reefs: evidence for potential use as refugia in a fishery management strategy.