CRITTER CONFIDENTIAL Spring has sprung !
Marine biologist Paul Naylor sets out some of the fascinating behaviour you can witness during the Spring season , when the reef gets jiggy with it
Yes , romance is in the air , or at least water , in the UK seas we love to explore . Leaving all the anthropomorphism aside , this is a great time of year to observe the intriguing breeding activity of many of our favourite animals . I am going to look at a few fabulous fish this month , and then follow on with invertebrates in the next issue .
Rocky reefs in shallow water are now looking beautiful in their own right , with fresh growths of thongweed , kelp and other algae .
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In their crevices , and in other nooks and crannies too , male tompot blennies can be seen guarding eggs laid by females .
A couple of things to look for are the specially enlarged anal glands ( shaped like cauliflowers ) on the male ’ s belly that he uses to wipe the eggs , and that the eggs in the layer may not all be the same colour . Those differing colours represent batches of eggs at varying stages of development , because they were laid at different times , probably by different females .
Corkwing wrasse building his impressive nest in a crevice under Swanage Pier
It ’ s not just the males that have multiple partners ; each female visits a good variety of males to bestow her precious bounty . Promiscuity to maximise success doesn ’ t mean lack of choosiness though ; both sexes are selective about their mates , because the eggs ( for females ) and territory ( for males ) are valuable investments .
Because males are choosy , there is a reason for rivalry between females as well the expected territorial disputes between males . I find it particularly intriguing that females appear to change their colour and adopt a paler shade when entering a male ’ s territory to lay eggs , but turn darker when interacting with potential competitors . Facets like this , along with that mutual choosiness of the sexes , make the social lives of tompots very complicated ; I ’ m only just starting to understand it after studying them for ten years ! [ see my ‘ Brilliant Blennies ’ page at marinephoto . co . uk ]
One of the aspects that I find makes tompot blenny behaviour particularly difficult to interpret is that , unless you get a clear view of the male ’ s enlarged anal glands , the sexes are difficult to tell apart at first glance . There is no such problem with breeding black-faced blennies ! These intriguing fish are relatively rare but can be seen regularly , often beneath overhangs , at certain spots along the western part of the South Coast .