Fish stocktake – the mysteries, the surprises and the wins
Blue-barred parrotfish (Scarus ghobban), last seen in September 2021
Back in January 2020, when I first began recording the biodiversity of Norfolk Island’s inshore lagoonal system, we were deep into a devastating drought. Our tank pumps were sucking dust, and the bores, supplied by the underground aquifer were empty. Once the drought broke in March 2020, we had good rainfalls until October 2023, before it dried up again in November 2023 leading to a deeper drought than the one in 2020, and which to date really hasn’t quite broken yet.
The only saving grace for the island’s residents is that the aquifer replenished during the 2022 rains. According to the Bureau of Meteorology, 2022 had the highest rainfall on record, with double the average rainfall seen in any of the previous five years; it is this aquifer that has kept many households going in recent months.
Information supplied by the Bureau of Meteorology
I mention all this because it was during 2022 that a few of our fish species seemed to go missing in action or, at the least, were present in diminished numbers. Were these population changes coincident with the increased flows of both overground water through the creek systems, and underground water leaching through the sand, into the lagoons that year? Was this extra water reducing the salinity in the bays, which then caused some species to leave? Or maybe there were increased nutrients being carried into the bay, which the fish were reacting to? Maybe it was neither of these factors and was just a naturally occuring cycle with the fish leaving to breed or find other food sources. Or a combination of all these factors?
Either way, below is a little of what I have observed.
fish stocktake
In my ‘Year in review for 2023 on Norfolk Island’s reef’, published in December 2023, I made a few observations about some of the fish species in our lagoons. I thought I would revisit some of these, because there has been so much additional fish activity just in the last couple of months.
Parrotfish
About our parrotfish, I said the following:
… looking back through my records, there are a few noteworthy observations that I feel would be worth investigating further. (NB The fish I’ve chosen to single out here are all ones that I would see regularly, not the ‘one offs’ or occasional visitors that find themselves inside the lagoon.) I have recorded five species of parrotfish on our inshore reef. Parrotfish are a subspecies of the broader wrasse family. I last spotted each of these species, as follows:
blue-barred parrotfish (Scarus ghobban): 14 September 2021
marbled parrotfish (Leptoscarus vaigiensis): 21 September 2021
Pacific bullethead parrotfish (Chlorurus spilurus): 3 October 2021
palenose parrotfish (Scarus Psittacus): 20 June 2022
surf parrotfish (Scarus rivulatus): 12 January 2023 (previously 14 November 2022).
Parrotfish were already thin on the ground in our lagoons, so for these species to all disappear was distressing, especially when considered in the context of the other species that seemed to disappear as well (refer to Year in review for 2023 on Norfolk Island’s reef). But, finally, I have some good news.
On 21 January 2024, I saw the first pale-nosed parrotfish – a pair of juveniles. These are still hanging around now (April 2024).
I saw a tiny juvenile marbled parrotfish that same day, 21 January.
And a surf parrotfish on 9 April.
In addition to these three very welcome sightings, I recorded a new (for me) species of parrotfish – a sixband parrotfish (Scarus frenatus) – in Slaughter Bay on 4 April 2024.
So why did we lose our parrotfish all around the same time, and why are they now back?
Let’s hope we’ve turned a corner and will see more of this fish family in the coming months.
Peacock damsels
I closely watched a tiny population of peacock damselfishes (Pomacentrus pavo) from February 2021, when they were juveniles to Deecember 2022 when they seemed to all leave the bays. At first, we had a population of five (that I knew about), but two disappeared, and by 28 December 2022, the three that remained in the Emily Bay vicinity all disappeared. Almost overnight. Just like that.
I can almost hear the cynics among you saying, ‘well so what about three tiny fish, and how do you even know they disappeared?’ As I have said before on this blog, Norfolk Island’s reef is small and intimate. We can count some species on one hand. And I am in there most days, so although I vary where I go, as a rule, I tend to know where the different species hang out. These damsels with their beautiful lapis lazuli blue scales, like tiny jewels, are a favourite of mine, so I am confident in my observations. They are highly territorial, living one per bommie as adults, spread widely across the lagoon; I would always make sure to check on them, minly because I was always trying to get a better photo!
Since that day in December 2022, I’ve been searching for them. I even wrote a blog post speculating about what may have happened to make them disappear: ‘The curious case of the peacock damselfish’.
Then on the 24 January this year I spotted three of the teeniest baby peacock damselfish over a bommie in the channel that had been upturned in a recent big surf. Over the next couple of weeks, I found more dotted around the reef. We are up to nine juveniles so far and I am still searching.
I have so many questions. Why did they disappear all at the same time? For breeding? (That seems logical.) But why were they gone for a whole year? Is this a pattern, so does that mean these new babies will remain for two years like the generation before, then disappear in December 2025 before new ones arrive in January 2027?
I have no idea, but I’ll keep watching and let you know! Good job I’m patient!
Stripeys
Back in October 2020, I recall being very excited to see an East-Australian Stripey (Microcanthus joyceae), a small yellow and black fish, hiding under a coral shelf in Slaughter Bay. It was the first time I’d seen one, so I waited patiently for a long time trying to get a decent photo. It was very reluctant to pop its nose out, even more so when a friend stopped by to say hello, while waving his arms and feet around like a windmill.
A few months later, at the opposite end of the lagoon, I spotted another three. Within a month there were five stripeys and hanging with them was one mado (eastern footballer, or Atypichthys latus). I wrote about them in a blog post ‘A little mado with attitude’ in February 2021.
Fast forward to September 2023, it was with much delight that I photographed a group of at least ten in Emily Bay. And as of yesterday, 20 April 2024, there were still a few remaining in this spot (it can be hard to tell when they flit and out of sight). However, in some really exciting news, down at Slaughter there were probably a further fifteen or so, with most together in one spot and a few outliers hiding under shelves nearby.
I know locals will say that these little fish were once plentiful in the bays, so it is wonderful to see them making a comeback.
My first sighting in October 2020
Five stripeys and a mado, March 2021
East-Australian Stripey (Microcanthus joyceae)
Other species that are on the rise
Also with noticeable increases in numbers are these three species of butterflyfish. In all three cases, I can remember being extraordinarily excited to see just one individual!
Masked bannerfish (Heniochus monoceros)
Chevron butterflyfish (Chaetodon trifascialis)
Raccoon butterflyfish (Chaetodon lunula).
New sightings
Apart from the sixband parrotfish, mentioned above, there have been other exciting discoveries to add to the species list inside the lagoons, At the time of writing (22 April 2024) two of these are completely new recordings for Norfolk Island, made in just the last week:
Barred thicklip (Hemigymnus fasciatus) - first time recorded here on Norfolk Island
Eclispe butterflyfish (Chaetodon bennetti) - first time recorded here on Norfolk Island
Merten’s butterflyfish (Chaetodon mertensii) - my first sighting
Pennant bannerfish (Heniochus chrysostomus) - my first sighting.
It is such a joy and a privilege to be able to witness these comings and goings firsthand. I am really looking forward to being able to delve more deeply into what drives the migrations of species in and out of the bays as I start work on my PhD in coming months.