able to recognise and follow more than 50 individuals in my study areas . I can ’ t pretend I don ’ t feel affection for these feisty little characters , but this technique has more to offer than mere sentimental value . It ’ s a powerful tool for uncovering more of the complex biology of this species .
I mention Bertram specifically because , as well as being one of the reef ’ s stalwarts , he has taught us a great deal . We already suspected there may be ‘ sneaker ’ male tompot blennies , which enter the home of territory-holding males and surreptitiously fertilise some of the eggs being laid by a female guest … then we spotted a small , young Bertram in action . It was unforgettable how he approached territory-holder Bradley ’ s residence , got chased away quickly but then returned a little later and furtively sidled up next to the visiting Blanche , before a now blind-sided Bradley eventually drove him off again !
The following year , we saw Bertram ‘ gain respectability ’ to become a territoryholder himself and , five years later , he is still there . This has also occurred with other recognised sneakers and is unusual biological information because , while sneaker males occur in many animal species from deer to cuttlefish , it is often not known whether sneakers become conventional males or if they use what is known as ‘ Alternative Reproductive Tactics ’ for life . As if that isn ’ t enough , Bertram is also one of the most impressive exponents of the dashing ‘ loop-swimming ’ courtship dances that we have found male tompot blennies perform when a female approaches their home .
Despite my particular enthusiasm for tompots , the point I am keenest to make here is that individual photo recognition can easily be applied to other species of fish . At one of my blenny study sites , I was aware of a large ballan wrasse that
A large ballan wrasse patrols a Devon reef in 2012
The pattern of spots on his head showed it was the same individual in 2014
often cruised the reef when we were there . Was it always the same one ? When I eventually had time to look through the relevant photos , the pattern of spots on his head did indeed show it was the same individual from at least 2012 to 2020 . I say ‘ his ’ here because size showed he was almost certainly now a male and I say ‘ now ’ because , unlike blennies , ballan wrasse change sex during their lives .
Another example of individual recognition came about unintentionally . I was closely examining two images of nursehounds taken several months apart at a local reef , simply to see if their eyes would help me distinguish them from smallspotted catsharks , when I realised that the pattern of pale and dark dermal
… and in 2020
denticles ( tiny teeth that are the shark equivalent of scales ) were identical on both photographs . It was the same nursehound !
I hope many readers are already familiar with the fabulous Undulate Ray Project , run by dedicated BSAC members principally in Dorset [ see March 2019 SCUBA ]. Using photographs of the beautiful patterns on the backs of these impressive animals and image analysis supported by specialist software , approximately 1,000 individuals have been identified . As so often with such research , amazing aspects of the species ’ movements and behaviour have been revealed . �
Paul ’ s photos and video clips capturing UK marine life stories are on Instagram @ paulnaylormarinephoto
The pattern of pale dermal denticles around the eye showed it was the same nursehound at the reef several months later
Close-up of a nursehound
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