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Impact of observers on fish diversity and size at common cleaner wrasse (Labroides dimidiatus) cleaning stations

 

 

Camille Demairé, Simona Colosio & Fausto Quattrini

University of Neuchâtel

Introduction

 

The common cleaner wrasse (Labroides dimidiatus) is a widespread fish species living among coral reefs all around the globe. Its role on this acquatic ecosystem is of remarkable importance since it "cleans" client fishes from ectoparasites present on their skin and mucus. This interaction takes place in specific areas named cleaning stations.  

This behavior hide several complex mechanisms also touching the concept of "Game theory".(2,6) For this and other reasons, L. dimidiatus has become a model species used in several studies based on interspecific interactions and fish cognition.(1,5)

 

 

 

 

 

 

 

 

         

 

 

 

 

 

 

 

 

 

 

 

 

 

 

“What we observe is not nature itself, but nature exposed to our method of questioning.”

Werner Heisenberg

 

Although many studies are generally conducted in the laboratory, some of these need to be based on field observations.(1,3-5,7) It seems that little attention has been paid on possible influences on fishes behaviour caused by the presence of one or more observers, which could create significant biasis on the data.(8) Such a scenario might imply a new and different consideration of fileld studies based on behavioural observations. Thus the main question of this work was:

 

Could the presence of one or more observers influences fishes behaviour at cleaning stations?

 

 

Methods

To answer this question, we conducted a pilot project in Dahab and Ras Mohammad National Park, Egypt, from the 1st to the 4th of June 2015.

We found and filmed nine different cleaning stations using a GoPro camera placed in front of them. The station areas have been chosen after an observation of the cleaner-clients interactions of about 10 minutes.

For each cleaning station, two videos of 15 minutes were made with and without the presence of two observers fitted with snorkel equipment.

 

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The first 5 minutes of recording were considered as acclimatation time and thus not analyzed. In the remaining 10 minutes, we noted the number of fish species and families present at the station as well as the maximal size as reported in the books: "Lieske E. &  Myers R. (2004) Coral reef guide: red sea; Allen et al.(2003), Reef fish identification: tropical pacific". 

 

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The data we recorded were analysed by mean of paired T-test with the software R-studio 3.2.2.

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Results & Discussion

Our results showed that, without observers, the number of fish families and species was significantly higher compared to the situation in presence of bystanders (Fig. 1 P-value= 0.0057, Fig. 2 P-value=0.0007). In a similar way, the mean maximal size of fishes was significantly higher when snorkels were absent (Fig.3 P-value=0.0011). 

 

We detected that the presence of observers at cleaning stations could have a remarkable impact on the diversity of fish species and families as well as the size of clients.


Thus, this pilot study suggests that other similar projects should be conducted in order to assess the amount of this impact and maybe consider this influence in further observational studies of cleaning stations.  

Some references to get started

  1. Adam, T. C. (2012). Mutualistic cleaner fish initiate trait‐mediated indirect interactions by influencing the behaviour of coral predators. Journal of Animal Ecology, 81(3), 692-700.

  2. Bshary, R. (2002). Biting cleaner fish use altruism to deceive image–scoring client reef fish. Proceedings of the Royal Society of London B: Biological Sciences, 269(1505), 2087-2093.

  3. Bshary, R., & Schäffer, D. (2002). Choosy reef fish select cleaner fish that provide high-quality service. Animal Behaviour, 63(3), 557-564.

  4. Grutter, A. S., Murphy, J. M., & Choat, J. H. (2003). Cleaner fish drives local fish diversity on coral reefs. Current Biology, 13(1), 64-67.

  5. Bshary, R., & Würth, M. (2001). Cleaner fish Labroides dimidiatus manipulate client reef fish by providing tactile stimulation. Proceedings of the Royal Society of London B: Biological Sciences, 268(1475), 1495-1501.

  6. Soares, M. C., Cardoso, S. C., Grutter, A. S., Oliveira, R. F., & Bshary, R. (2014). Cortisol mediates cleaner wrasse switch from cooperation to cheating and tactical deception. Hormones and behavior, 66(2), 346-350.

  7. Clague, G. E., Cheney, K. L., Goldizen, A. W., McCormick, M. I., Waldie, P. A., & Grutter, A. S. (2011). Long-term cleaner fish presence affects growth of a coral reef fish. Biology letters, 7(6), 863-865.

  8. Titus, B. M., Daly, M., & Exton, D. A. (2015). Do Reef Fish Habituate to Diver Presence? Evidence from Two Reef Sites with Contrasting Historical Levels of SCUBA Intensity in the Bay Islands, Honduras. PloS one, 10(3), e0119645.

References
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