By Lize Gibson-Hall
We are excited to welcome Lize Gibson-Hall to share this blog article with you all! Thank you for reading, if you would like to share your climate action story get in contact with us at climateactionplymouth@gmail.com – Lorraine
To local divers and wild swimmers, the common cuttlefish (Sepia officinalis) is a frequent treat, inhabiting the Devon and Cornish coast from spring to summer. However, for many living in Plymouth and the surrounding areas, this alien creature remains mysterious. A cuttlefish is from the family cephalopod which means ‘head foot’. They may be most well known for their incredible camouflage, with some even mimicking crabs and outsmarting larger males by imitating females.
They have a short life span of 1 to 2 years, with mortality occurring soon after spawning in females (Bloor et al., 2013). Due to their short lifespan and death after spawning, these animals require successful recruitment to replace the dying population, making them somewhat vulnerable to climate change if successful recruitment doesn’t occur (Gibson-Hall & Wilson, 2018). In our waters, we have a subpopulation, separated from the Mediterranean population due to previous bottlenecks through sea level changes (Pérez-Losada et al., 1999).
Vulnerability to Climate Change
The common cuttlefish, similar to many other cephalopods, are very adaptive to differing climatic conditions but research on the true adaptive nature of this species is limited. In response to rising temperatures, this cuttlefish will increase its metabolism and begin to eat far more with a thermal limit of 10-30°C (Guerra, 2006). They are also able to reduce their oxygen consumption in times of hypoxia, whilst decreasing their metabolic rate (Capaz et al., 2017).
Despite this recorded adaptability, cuttlefish are at their most vulnerable when they are developing in their eggs and just after hatching. They not only have to face the immediate predatory risk but require far more specific temperature and environmental conditions for successful development (Paulij et al., 1990; Cronin et al., 2000; Guerra et al., 2016).
Although many UK residents are hoping for a warm summer, the increase in global temperatures is having unprecedented impacts on wildlife. Development in the egg increases with temperature and could see our resident cuttlefish reaching sexual maturity far earlier and, unfortunately, reducing their life span (Skyes et al., 2006). An issue with this is the increased speed of hatching, resulting in much smaller cuttlefish. It may be adorable to see such tiny cuttlefish but this increases the risk of predation.
Currently, our cuttlefish migrate to offshore, deeper, areas during the winter period but remain coastal in warmer waters (Wolfram et al., 2006). With the oceans continuing to warm we could see cuttlefish remaining in shore for longer whilst increasing their spawning period. However, warmer waters are also attractive to other species, especially the invasive blue crab Callinectes sapidus. This crab has already reached UK waters after expanding its range and enjoys feeding particularly on cuttlefish eggs (Nehring, 2011). As the cuttlefish lays its eggs along the shore its strategy is to produce as many eggs as possible and to continue moving. The strategy the cuttlefish employs, is to coat the eggs in black ink for further protection but is not physically here to protect them leaving the population somewhat vulnerable.
Importance of Seagrass
We cannot talk about the impacts of climate change on cuttlefish without mentioning one of their most important habitats in the UK. Seagrass beds are a beautiful feature of Plymouth Sound and are home to a wide variety of important species from seahorses to fish (Jackson et al., 2001).
One of the chosen spawning spots and ‘hang out’ sites for young and juvenile cuttlefish are seagrass beds (Blanc & Daguzan, 1998). These areas are commonly sheltered and, therefore, more protected from environmental conditions such as storms (Bloor et al., 2013). They also allow structures for the eggs to be placed on, including seaweeds, seagrass itself and dead structures. This elevates the eggs, reducing the risk of predation (Bloor et al., 2013). Unfortunately, these seagrass beds are also becoming vulnerable to climate change and anthropogenic activities, namely fishing.
Fishing Industry
Their apparent survival through our changing seas may make them a more prized fishing item, with cephalopod fishing predicted to increase as ‘the big 5’ (cod, haddock, tuna, salmon, prawn) decrease in our oceans. If you just pop down to Brixham harbour you can see the hoards of common cuttlefish landed daily. If practiced sustainably, this could be a solution to the overfishing crisis but fishing of these cuttlefish in the UK are unregulated and only increasing (Davies & Nelson 2018). This was the topic of my undergraduate dissertation and was both interesting and somewhat alarming to see the continuing increase in landings over time without any apparent change to regulation or monitoring. This is an important aspect to consider as it is an added stressor on top of climate change and is even more impactful if cuttlefish are caught before they have had a chance to spawn.
What Can You Do
Plymouth is an amazing city to get involved with conservation and protection of our coasts. The national marine aquarium is working to protect, survey, and replant seagrass beds with The Seagrass Restoration Project. This project is sometimes looking for divers to get involved, but these ecosystems, as well as cuttlefish, tend to suffer from lack of public knowledge and government protection. There is always a need for people to share the importance of seagrass as well as the beauty and uniqueness of cuttlefish.
If you are lucky enough to be a recreational diver, the Cephalopod Citizen Science Project is also on the lookout for any images or sightings of cephalopods in the UK to gain a better understanding of hotspots, breeding grounds and migration timings.
Cuttlefish has now been placed onto the list of food you should avoid eating (Marine Conservation Society, UK), due to the unsustainability of the fishing method and the lack of awareness of the population status. It is worth spreading this information to people you known and remembering if you every come across it on the menu. This is of especial interest to the newly founded charity, the Cuttlefish Conservation Initiative who are looking into research, lobbying and fishing of cuttlefish in the UK. This group was formed by Plymouth Universities own masters’ students and is an amazing project to keep an eye on.
Finally, even participating in a beach clean can reduce the amount of pollution moving immediately into surrounding seagrass beds, reducing the stress on the environment. Finally, you can support your local wildlife trust (i.e., Devon and Cornwall) through volunteering and donating, to assist in their work with fisherman and local governments to raise awareness of the needed protection for these creatures.
Lize is currently completing a Masters degree at Plymouth University in Zoo Conservation Biology, after completing her undergraduate studies in Marine Biology. She has a particular interest in conservation and understanding the future vulnerability of animals under climate change. Her species of interest are: cuttlefish, sloths, bats and orangutans. In her spare time she enjoys photography, diving. You can find Lize on her social media platforms here: LinkedIN and Instagram and you can read her Blog here: https://thetravellinggoth.wixsite.com/lizemaeve
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