The Blackstripe Sweeper (Pempheris schwenkii) is also known as Schwenki’s Sweeper , Striped Bullseye,Silver Bullseye and Black-edged Sweeper. They are common fish on Tanzanian Reefs and are often found in extremely large numbers around caves and overhangs during the day. Research seems to indicate that there may be various sub species within the distribution range.
The Blackstripe Sweeper has a very distinctive hatchet shaped body, the shape is unmistakable. The more juvenile Blackstripe Sweeper which can be seen in the image immediately below, is more of a pinkish green translucent colour compared to the adult. Adults have a more coppery green coloured body.
They grow up to 12 cm in length but appear larger because of the depth of the body. Because of their nocturnal feeding habits, they have proportionately large eyes which allow better night vision. They obtain their common name from the black stripe that runs up the anal fin.
BLACKSTRIPE SWEEPER IN THE WILD
The Blackstripe Sweeper are nocturnal feeders and during the day collect in large shoals under overhangs and in caves. The shoals can often be very dense and of quite some size. The shoals are often made up of various sub shoals as fish of a certain size will shoal together. The larger full grown specimens will often move above or outside the feature in which they hiding in. At night the shoals disperse to feed on plankton.
They are known to produce sounds and adult males seem to be able to produce the loudest sounds indicating that sound production may be mating related.
The Blackstripe Sweeper is found from East London in South Africa to the Red Sea and across to Southern Japan and down to Australia where they are known as Silver Bullseyes . They are found from 3 meters down to 30 meters.
The Blackstripe Sweeper are nocturnal feeders , feeding mainly on zooplankton. Once it is dark they swim above the substrate and feed on the zooplankton. On one night dive when we were diving on a large coral bommie, a large shoal came and sat a few meters above us clearly feeding on organisms attracted by the lights. As soon as we moved upwards towards the shoal they dispersed. Otherwise they are usually seen singular or in small groups at night.
Little seems known about their breeding habits although it seems that breeding is not tied to the moon cycles.
Blackstripe Sweeper are not commonly kept in private aquariums. Sometimes they can be seen in large public aquariums.
BLACKSTRIPE SWEEPER CLASSIFICATION