Whale Sharks show remarkable capacity to recover from injuries,
including partial fin re-growing

Date:
February 23, 2021
Source:
University of Southampton
Summary:
A new study has for the first time explored the extraordinary rate
at which the world's largest fish, the endangered whale shark,
can recover from its injuries. The findings reveal that lacerations
and abrasions, increasingly caused through collisions with boats,
can heal in a matter of weeks and researchers found evidence of
partially removed dorsal fins re-growing.



FULL STORY ==========================================================================
A new study has for the first time explored the rate at which the
world's largest fish, the endangered whale shark, can recover from its injuries. The findings reveal that lacerations and abrasions, increasingly caused through collisions with boats, can heal in a matter of weeks and researchers found evidence of partially removed dorsal fins re-growing.


==========================================================================
This work, published in the journal Conservation Physiology, comes at
a critical time for these large sharks, that can reach lengths of up
to 18 metres. Other recent studies have shown that as their popularity
within the wildlife tourism sector increases, so do interactions with
humans and boat traffic. As a result, these sharks face an additional
source of injury on top of natural threats, and some of these ocean
giants exhibit scars caused by boat collisions. Until now very little
was known about the impact from such injuries and how they can recover.

"These baseline findings provide us with a preliminary understanding of
wound healing in this species" says lead author Freya Womersley, a PhD
student with University of Southampton based at the Marine Biological Association, UK. "We wanted to determine if there was a way of quantifying
what many researchers were anecdotally witnessing in the field, and so we
came up with a technique of monitoring and analysing injuries over time."
The unique spot markings of whale sharks allow researchers across the
world to identify individuals and monitor regional populations, making
use of websites such as WildBook where people can upload photos of their
shark sightings. For this study, the research team examined photographs
taken by citizen scientists, researchers and the whale shark tourism
industry in two sites in the Indian Ocean where the sharks frequently
gather, and used these markings to standardise between images. This
method allowed the team to compare photographs taken without specialist equipment over time and increased the amount of data available to assess
and monitor how individual wounds changed.

"By using our new method, we were able to determine that these sharks can
heal from very serious injuries in timeframes of weeks and months" says
Freya. "This means that we now have a better understanding of injury
and healing dynamics, which can be very important for conservation
management." The study also highlighted whale sharks' capability to
re-grow a partially amputated first dorsal fin, which, to the authors' knowledge, is the first time a shark has ever been scientifically
reported exhibiting this phenomenon. Of further interest, their unique
spot markings were also observed forming over previously injured spots,
which suggests that these beautiful markings are an important feature
for this species and persist even after being damaged.

These healing capabilities suggest that whale sharks may be resilient to impacts caused by humans, but the authors of this work note that there
may be many other less recognisable impacts of injuries to these animals,
such as reduced fitness, foraging capacity and altered behaviours; so
injuries need to be prevented where possible. They also found variation
within healing rates, with lacerations, typical of propeller injuries,
taking longer to heal than other kinds of wounds, highlighting the need
for further research to determine the influence of environmental and
more nuanced individual factors on injury healing.

Careful management of whale shark aggregation sites, which occur
seasonally at a number of coastal regions around the world, is essential
to ensure the sharks are protected while spending time in areas of
high human activity. If sharks are encountered with injuries in these locations, research such as this can help local teams estimate how old
the injury is and make assessments about where and how it might have
been inflicted based on knowledge of whale shark movements and tendency
to return to the same locations.

Recent research published in Nature found that 71% of pelagic sharks
have declined over the last 50 years, and highlighted the need to enforce stricter protections for this important group of ocean inhabitants.

Freya concludes, "Whale sharks have been experiencing population
declines globally from a variety of threats as a result of human
activity. Therefore, it is imperative that we minimise human impacts
on whale sharks and protect the species where it is most vulnerable,
especially where human-shark interactions are high.

"There is still a long way to go in understanding healing in whale
sharks, and in shark species in general, but our team hope that baseline studies such as this one can provide crucial evidence for management
decision makers that can be used to safeguard the future of whale sharks." ========================================================================== Story Source: Materials provided by University_of_Southampton. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Freya Womersley, James Hancock, Cameron T Perry, David Rowat. Wound-
healing capabilities of whale sharks (Rhincodon typus) and
implications for conservation management. Conservation Physiology,
2021; 9 (1) DOI: 10.1093/conphys/coaa120 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/02/210223110500.htm

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