Things that go bump in the night

To get as complete a species list as possible we need to survey different habitats, different seasons and also during the day and at night. Some species remain well hidden during daylight hours when the plethora of fish predators make leaving the safety of the crack or crevice hazardous. When night arrives the seabed is littered by the sleeping bodies of the black fish and out comes a different array of animals. The striking red reef lobster, the small red scorpionfish, giant stretchy yellow banded sea cucumbers, many species of shrimps are just a few who we don’t see through the day. To quantify the difference in species diversity and abundance the SMSG team prepared for some day night comparison surveys.

The survey method was adapted slightly (to compensate for reduced visibility at night) and involved three transects each 1m x 50m survey all along the rocky reef just off Wigan Pier. During the early afternoon Judith, Paul and Martin conducted the first set of transects – leaving the tape measures in situ with activated glow sticks on each end. As darkness fell the divers returned to the pier – Judith with a dive torch strapped to her head to allow her to count and write. This worked well except for that many small amphipods and worms which were attracted to the light at night meaning she had a constant swarm of critters buzzing around her head for the entire dive. Longspine black sea urchin were the most abundant to count with several hundred on each transect but the most exciting critter was an orange nudibranch – usually only found well hidden under rocks. After an 84 minute dive the team were all happy to return to the dive club to a pot of traditional St Helenian pilau cooked by Elizabeth on the BBQ.