Seasonal variations in fish species richness in Nelson Bay
April 25, 2012 by Toni · Leave a Comment
Informal report on RLS surveys by RLS survey diver Tom Davis
RLS surveys have been conducted at the Halifax Divesite in Nelson Bay for several years. More intensive surveying has been conducted in the last 18 months, however, due to concern over sand movement causing damage to the site. Surveys have been conducted at the site every 2 months since October 2010 to assess recovery from this disturbance. As an added bonus, these repeated surveys also provide an insight into seasonal variations in fish diversity in the region, which is heavily influenced by the East Australian current.
Surveys have been conducted on 2 transects at Halifax, with each survey starting at a known landmark on the reef. One transect is at a depth of 8m on the Eastern side, and the second transect is at a depth of 11m on the Western side.
Figure 1 shows the trend over the last 18 months in the average, across the 2 transects, of the total number of fish species encountered on each transect, along with average water temperatures over the same interval. Species richness at the site has followed a very clear seasonal trend, tracking changes in water temperature. The East Australia Current is known to sweep a host of tropical species into Nelson Bay over the summer, and the marked seasonality in species richness is primarily due to patterns of recruitment by tropical species, which apparently either emigrate or die-off during the cooler months.
Figure 2: Comparison of average water temperature and average number of species at Halifax
To date more than 250 species of fish have been identified on RLS surveys in the Port Stephens area. Table 1 shows the most common species with temperate and tropical or sub-tropical affinities recorded on transects in Nelson Bay. Note that while many of the tropical/sub-tropical species are only found during summer, some of these are also regularly encountered during winter; for example Parupeneus spilurus and Stethojulis interrupta.
| Common temperate species | Common tropical/sub-tropical species | ||
| Latin Name | Common Name | Latin Name | Common Name |
| Hypoplectrodes maccullochi | Half-banded seaperch | Parupeneus spilurus | Black spot goatfish |
| Notolabrus gymnogenis | Crimson-banded wrasse | Stethojulis interrupta | Cut-ribbon wrasse |
| Ophthalmolepis lineolata | Maori wrasse | Thalassoma lunare | Moon wrasse |
| Parma microlepis | White-ear | Chaetodon guentheri | Gunthers butterflyfish |
| Scorpaena jacksoniensis (formerly S. cardinalis) | Red scorpion cod | Labroides dimidiatus | Cleaner wrasse |
| Cheilodactylus fuscus | Red morwong | Cheilinus bimaculatus | Two spot maori wrasse |
| Atypichthys strigatus | Mado sweep | Cirrhilabrus punctatus | Small spotted wrasse |
| Achoerodus viridis | Blue groper | Pomacentrus coelestis | Neon damsel |
| Mecaenichthys immaculatus | Immaculate damsel | Halichoeres nebulosus | Clouded wrasse |
| Chromis nitida | Yellow-back puller | ||
Table 1: Common Temperate and Tropical Species in Nelson Bay
To date there is little evidence that sand movement at Halifax has had a significant impact on fish species at the site, however there is no question that sand inundation has devastated much of the site’s sponge gardens. Monitoring is ongoing and hopefully in the future the sponge gardens will recover. In the meantime, Halifax is still a fantastic place to see a wide variety of fish species, especially in Autumn!
For more information on diving in Nelson Bay see divingnelsonbay.weebly.com
Sydney Survey Weekend 16-19th March 2012 by Margo Smith
April 25, 2012 by Toni · Leave a Comment
After the number of tropical low pressure systems over Sydney in the lead up to this year’s trip, everyone had been closely watching the weather forecasts with fingers crossed hoping we would not have a repeat of Sydney 2011.
Port Phillip Bay 7-12th Feb 2012
March 2, 2012 by Toni · Leave a Comment
After 4 years of enduring winter surveys in Port Phillip Bay, the RLS team had the luxury of trialling a summer survey trip… or so they thought!  It turns out the Victorian summer isn’t all that crash hot either!  The small crew of Don Love, Jen Hoskin, Sylvia Buchanan, Tim Crawford and Toni Cooper conquered some bad vis and strong winds, but by the end of the week everyone was still smiling and had heaps of surveys to show for it!
Rottnest Island survey weekend 20th-23rd May
July 18, 2011 by Toni · Leave a Comment
The fourth annual RLS Rottnest Island survey weekend proved yet another success, with the majority of sites surveyed by an excellent group of RLS divers, all with much appreciated help from the Rottnest Island Authority.
Port Phillip Bay survey weekend 6th- 11th May.
July 15, 2011 by Toni · Leave a Comment
A small group of Victorian and NSW divers headed down to Queenscliff for the Port Phillip Bay annual survey weekend.
Jervis Bay 14th-18th April 2011
May 24, 2011 by Toni · Leave a Comment
Once again, another crack team of NSW RLSers travelled to Jervis Bay for a great weekend of surveying on board Ocean Trek.
Sydney survey weekend 25-28th March
May 3, 2011 by Toni · Leave a Comment
RLS divers from Port Stephens, Newcastle and Sydney recently got together to re-survey a bunch of RLS annual reef monitoring sites in the Sydney area.
Spotted handfish surveys – Derwent River, 12th – 13th March 2011
March 24, 2011 by Toni · Leave a Comment
The Derwent Estuary Program recently initiated a recovery project for the endangered spotted handfish, with RLS assisting to establish a core group of local divers that can assist in monitoring a couple of key handfish populations in the Derwent Estuary. The second survey weekend for this project was held over the 12th and 13th March to survey handfish not far from the centre of Hobart and, like the first, was incredibly successful.
Cape Howe, Eastern Victoria (2nd-5th Feb)
February 17, 2011 by Toni · Leave a Comment
A very small crew headed up to Mallacoota for a short, intensive survey weekend of the Cape Howe region. Read more
Spotted handfish surveys – Derwent River (8th-9th Jan 2011)
February 9, 2011 by Toni · Leave a Comment
The Derwent Estuary Program recently initiated a recovery project for the endangered spotted handfish, with RLS assisting to establish a core group of local divers that can assist in monitoring a couple of key handfish populations in the Derwent Estuary.
