Predation of juvenile reef fish in coral patches at Ningaloo Reef

The second research article I have decided to discuss is one I had the pleasure to be involved with!  In fact, it was the first paper I was a co-author on, after linking up with the Department of Environment and Conservation through an ANNiMS internship program.  The paper was recently published in the journal Coral Reefs, and can be found here!

Chromis sp. on a coral patch in Ningaloo Reef

The little juvenile fish we used to fertilize our coral patches…so who eat’s them, and when!?

We know that predation events structure communities in many ecosystems, but this effect could be particularly important in coral reefs.  Juvenile reef fish that are newly settled on a coral reef patch can be extremely vulnerable to predation attacks.  However, we know very little about predation on juvenile coral reef fish in all but a few ecosystems worldwide.  Given the lack of empirical data in most marine systems, we tried to find out which fish was responsible for the predation encountered at Ningaloo Reef in Western Australia (as a side note, Ningaloo Reef is a beautiful place – recently granted World Heritage Status – that everyone should visit if they get the chance… but I will be writing about it a bit later on in more detail!)

To do this, we “fertilised” some coral patches with juvenile reef fish while leaving others untouched (i.e. no juvenile reef fish), and filmed what happened over the course of the day!  We even used special lights to allow us to see what was happening during the first couple of hours of darkness!  We ended up with 199 hours of video recordings, where we identified all fish within 30cm of the patch, measured how long they spent within the vicinity and whether or not they tried to eat one of the juveniles!

We discovered that, unlike most other locations, predation of juvenile reef fish at Ningaloo Reef is concentrated during mid-afternoon times, instead of the normal dusk/dawn periods. We also found an unexpected candidate for the top predator of juvenile fish at Ningaloo Reef…..the moon wrasse (Thalassoma lunare).  In fact, of all the predatory strikes we seen on the videos, the moon wrasse was responsible for over 75% of them!  The interest of the moon wrasse towards the juvenile fish was highlighted by them spending significantly longer around the patches ‘fertilized’ with juvenile fish compared with control patches with no juveniles.

The really cool thing about this research is that it displays just how unique Ningaloo Reef is.  Firstly, predation of juvenile fish primarily occurred during the middle of the day, contrary to what we see in most other coral reef environments – a rise in predation during dawn and dusk.  And on top of this, the moon wrasse hasn’t been identified as a major predator of juvenile fish in other ecosystems.  However, in Ningaloo Reef, they appear to be responsible for a large proportion of juvenile fish predation, at least in corymbose coral patches where their slender body shape is ideal for hunting!

ResearchBlogging.org

Holmes, T., Wilson, S., Vanderklift, M., Babcock, R., & Fraser, M.W. (2012). The role of Thalassoma lunare as a predator of juvenile fish on a sub-tropical coral reef Coral Reefs, 31 (4), 1113-1123 DOI: 10.1007/s00338-012-0934-8

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One thought on “Predation of juvenile reef fish in coral patches at Ningaloo Reef

  1. do the perfect golf swing

    G’Day! Marineecologist,
    Neat Post, Ok hears the plan. I purchased a juvenile GSP and he’s in a slightly brackish 45 gal. environment with a juvenile cichlid who runs a large black slab stone multi cave structure on the left (*he loves the large cave on the first floor which has a back door.) There are also 4 sail fin platys’ who move way to fast for predation and likewise two Blood Fin Tetras who unlike there profile who say, are pretty aggressive and nosy; but very fast as well.
    Anyway I understand this cute little puffer has a very special diet. while he’s in the community (until he starts to need a more saline environment) how can insure his diet? I feed a combination of Beta pellets and one good meal of blood worms for all of’em. I am considering buying small ghost shrimp (live) but I think the cichlid may get to ’em first as the GSB is still quite small ( about 1-1/4″)
    There is also lots of plants, but I have a natural pea stone substrate with mixed geocites and black/quarts
    slate pieces.
    Nice One!

    Reply

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