It is commonly held that depth distributions of stony corals are mediated by environmental factors such as light levels and water motion, as well as biological interactions such as competition and predation. It is also commonly held that these mechanisms control the survival of coral larvae when they settle. In other words, the coral larvae will settle non-differentially over a wide depth gradient and they either survive or perish based on the previously mentioned factors. This study takes a different view and proposes that coral larvae preferentially choose where to settle based on the substratum of the parental habitat. That is to say that larvae of corals that are normally found in shallow areas, will preferentially settle in shallow areas, corals from deeper areas will settle there while those with wide depth distributions will show no preference.

In order to test this hypothesis six coral species were chosen at a study site on the Great Barrier Reef. These six species showed a marked difference in depth distribution. The study site was Pelorus Island, which lies about 18 km off the eastern Australian coast in the central Great Barrier Reef. Being so close to the mainland, water clarity was low with 8 to 10 meters visibility the norm.

Table 1 shows the species and their relative abundances by depth as determined by belt transect surveys. Clay paving tiles were placed at 2 m and 12 m depths and conditioned by leaving them there for 8 weeks bolted to concrete blocks. The experiment consisted of placing three tiles from each depth plus three unconditioned tiles in open system tanks with one species of coral larvae (several thousand to several hundred depending on the species). The larvae were added and then given 10 days to settle and undergo metamorphosis after which time the tiles were examined and the settled corals counted.

The results showed a distinct preference by the larvae for tiles from the parental habitat. Both Goniastrea species showed a high affinity for the 2 m tiles over the 12 m and unconditioned tiles. The two fungid species showed an affinity for the deeper tiles, and the Platygyra and Leptoria species showed a nearly equal distribution between 2 m and 12 m tiles.

The tiles were also examined for the organisms that had grown on them while they had been on the reef. The difference in distribution of the Goniastrea species was mirrored by the abundance of crustose red coralline algae on the 2 m tiles. Deeper water tiles had a greater abundance of tunicates, bryozoans, sponges and polychaete worms. Zone-specific coralline algae, bacteria and microalgae that have been shown to be important settlement cues in other studies were unfortunately, not examined in this study.

Although this study shows that settlement can be induced by the presence of depth-related organisms, it was not 100%. Therefore, other cues also play a role in the choice of settlement site by the coral larvae i.e. light intensity and spectral quality. More importantly, this study shows that, when given a choice, coral larvae can actively choose where to settle. This suggests that the depth distribution of adult colonies is influenced by patterns established at settlement and that these settlement cues are most likely species specific.

This study may have implications for commercial live coral aquaculture operations that hope to supply the aquarium hobby with captive grown corals via sexual reproduction of coral planulae. Unless the proper settlement cues are available, recruitment may be lower than desired. For this reason, knowledge of not only the natural distribution of a coral species over a depth range but also the fouling communities found at these locations might be critical for those species with narrow depth distributions.

Olivotto, I, Cardinali, M., Barbaresi, L., Maradonna, F. and O. Carnevali. 2003. Coral reef fish breeding: the secrets of each species. Aquaculture 224(1-4):69-78. Email: [email protected]

I must confess, when I first came across this paper, I thought I had hit the holy grail of ornamental fish aquaculture! However, that excitement quickly dissipated like a pack of killer rabbits on a Holy Knight trail when I read the paper. The paper describes the first successful rearing of the yellow tail damselfish, Chrysiptera parasema. I am not sure how this relates to the secrets of each species, since they only bred the one species, but fear not, read on.

The researchers set up four breeding pairs of damsels that had been purchased at a local pet store in Bergamo, Italy, by buying eight damsels and placing them in the same 120 liter tank. Once they began to pair up they removed each pair to their own 80 liter tank. Spawning began approximately three months after the pairs were placed in their own tanks. The tanks were kept at 28 oC, salinity of 30 ppt and with a photoperiod of 13 hours of light and 11 hours of darkness (13:11).

The males construct a nest under a rock and then entice the female inside where she deposits several hundred eggs. After 7 days the rock with the eggs attached were moved to hatching bucket and within two hours of darkness the eggs began to hatch and then were moved to the rearing tanks. Rearing tanks consisted of 25 liter tanks with water that was neither filtered nor aerated since the larvae are very delicate and very sensitive to any turbulence. The sides of the tank are covered so that light can only enter from above. Chlorella and Isochrysis algae were added to tank such that the bottom of the tank was no longer visible. Approximately 15% of the water was changed every day and two to three drops of a 5% potassium iodide solution was added twice a day to help with metamorphosis. Eggs batched were divided into different groups so that the affect of different photoperiods could be evaluated. Three different photoperiods were used 13:11, 16:8 and 24:0 to raise various replicate groups of larvae.

The larvae still have yolk sacs at hatching but these are consumed within 24 hours so a first food must be introduced soon after hatching or the larvae will quickly starve. The first food used was the common rotifer Brachionus plicatilis at a density of 20 rotifers per mL, any greater density resulted in larval die-off due to reduced oxygen levels. Rotifers were enriched using Selcon per manufacture’s recommendations. At day 19 from hatching, a second food was used, live, newly hatched Artemia at a density of 5 nauplii/mL, from INVE technologies in Belgium. These commercial decapsulated brine shrimp cysts are already enriched by the company with HUFAs (highly unsaturated fatty acids).

The results showed a marked difference in survival between the different photoperiods. Those larvae fed unenriched foods lasted only 48 hours. Those fed enriched rotifers under a photoperiod of 13:11 died within 3 days. Those under the 16:8 photoperiod died after 7 days and those under the 24:0 photoperiod survived until settlement at day 17 with a survival rate of 25%. The 24 hour light group not only survived better but grew faster as well. The increased survival under a 24 hours light régime has also been noted for black porhy, gilthead seabream and rabbitfish. However, other fish species have been reported to have better success under 16 or 18-hour régimes. This points out the need to assess the importance of photoperiod for each genus of fish that you are trying to breed.

Ishi B. I. and K. J. McGlathery. 2003. Effect of ultraviolet light on dissolved nitrogen transformations in coastal lagoon water. Limnology and Oceanography 48(2):723–734.

This study looked at the effect of ultraviolet radiation on the production of inorganic nitrogen, urea, and amino acids from aquatic dissolved organic matter (DOM) in the waters from Hog Island Bay, a coastal lagoon in Virginia. Samples from distinct sources of DOM to the lagoon were subjected to UV light mimicking the natural solar spectrum. It was found that dissolved organic nitrogen concentrations did not change measurably during the 36-h incubation, while calculated dissolved organic carbon concentrations dropped by up to 17%. Nitrate and urea levels were not consistently altered in the light, while ammonium photoproduction rates of up to 0.032 µmol N L-1 h-1 were observed. However, it was felt that the rates of ammonium and amino acid formation, when scaled up to estimate photoproduction in the lagoon system, appeared to be minor relative to other sources to and fluxes within the lagoon. What was of greatest interest to me about this study was that the calculated dissolved organic carbon (DOC) concentrations dropped by up to 17%. Activated carbon is often used in aquaria for removing DOC’s but it is also possible to reduce the level of DOC using ultraviolet light and ozone. The combined use of UV (or ozone) and carbon may prolong the useful life of activated carbon or other products that remove DOCs.

Recent Publications

Anemones

1. Acuna, F.H., Excoffon, A.C., Zamponi, M.O. and L. Ricci. 2003. Importance of nematocysts in taxonomy of acontarian sea anemones (Cnidaria, Actinaria). A statistical comparative study. Zoologischer Anzeiger 242(1):75-82.

Cephalopods

1. Kier, W.M. and A.M. Smith. 2002. The structure and adhesive mechanisms of octopus suckers. Integrative and Comparative Biology 46(6):1146-1153.

Corals

1. Anthony, K.R.N. and O. HoeghGuldberg. 2002. Variation in coral photosynthesis, respiration and growth characteristics in contrasting light microhabitats: an analogue to plants in forest gaps and understoreys? Functional Ecology 17(2):241-259.
2. Bhagooli, R. and M. Hidaka. 2003. Comparison of stress susceptibility of in hospite and isolated zooxanthellae among five coral species. Journal of Experimental Marine Biology and Ecology 291(2):181-198.
3. Brooke, S. and C.M. Young. 2003. Reproductive ecology of a deep-water scleractinian coral Oculina varicosa from the southeast Florida shelf. Continental Shelf Research 23(9):847-858.
4. Bongiorni, L., Shafir, S., Angel, P. and B. Rinkevich. 2003. Survival, growth, and gonad development of two hermatypic corals subjected to in situ fish-farm nutrient enrichment. Marine Ecology Progressive Series 253:137-145.
5. Clode, P.L. and A.T. Marshall. 2003. Variation in skeletal microstructure of the coral Galaxea fasicularis: effects of an aquarium environment and preparatory techniques. Biological Bulletin 204(2):138-145.
6. Clode, P.L. and A.T. Marshall. 2003. Skeletal microstructure of Galaxea fasicularis export septa: A high resolution SEM study. Biological Bulletin 204(2):146-158.
7. Goulet, T.L. and M.A. Coffroth. 2003. Stability of an octocoral-algal symbiosis over time and space. Marine Ecology Progressive Series 250:117-124.
8. Harriott, V.J. 2003. Can corals be harvested sustainably? AMBIO 32(2):130-133.
9. Kerswell, A.P. and R.J. Jones. 2003. Effects of hypo-osmosis on the coral Stylophora pistillata: nature and cause of “low salinity bleaching”. Marine Ecology Progressive Series 252:145-154.
10. Miller, S.W., Hayward, D.C., Bunch, T.A., Miller, P.J., Bull, E.E., Bardwell, V.J., Zarkower, D. and D.L. Bauer. 2003. A DM domain protein from a coral Acropora millepora, homologous to proteins important from sex determination. Evolution and Development 5(3):251-259.
11. Orejas, C., Gili, J.M. and W. Arntz. 2003. Role of small plankton communities in the diet of two Antarctic octocorals ( Primnoisis antarctica and Primnoella sp.). Marine Ecology Progressive Series 250:105-116.
12. Stillman, J.H. 2003. Sunny side up for hot corals. Journal of Experimental Biology 206(9):1435-1436.

Diseases

1. Farto, R., Armada, S.P., Montes, M., Guisande, J.A., Pereze, M.J. and T.P. Nieto. Vibrio lentus associated with diseased wild octopus ( Octopus vulgaris ). Journal of Invertebrate Pathology 83(2):149-156.
2. Pantos, O., Cooney, R.P., LeTessier, M.D.A., Barer, M.R., O’Donnell, A.G. and J.C. Bythell. 2003. The bacterial ecology of a plaque-like disease affecting the Caribbean coral Montastrea annularis. Environmental Microbiology 5(5):370-382.
3. Yambot, A.V., Jong, Y.L. and H.H. Sung. 2003. Characterizations of Cryptocaryon irritans, a parasite isolated from marine fishes in Taiwan. Diseases of Aquatic Organisms 54(2):147-156.

Filtration

1. Bomo, A.M., Husby, A., Stevik, T.K. and J.F. Hanssen. 2003. Removal of fish pathogenic bacteria in biological sand filters. Water Research 37(11):2618-2626.
2. Chen, Y.H., Chang, C.Y., Chiu, C.Y., Yu, Y.H., Chian, P.C., Ku, Y. and J.N. Chen. 2003. Dynamic behaviour of ozonation with pollutant in a counter current bubble column with oxygen mass transfer. Water Research 37(11):2583-2594.
3. Du, G.C., Geng, J.J., Chen, J. and S.Y. Lun. 2003. Mixed culture of nitrifying and denitrifying bacteria for simultaneous nitrification and denitrification. World Journal of Microbiology and Biotechnology 19(4):433-438.

Fishes

1. Asoh, K. and T. Yoshikawa. 2003. Gonadal development and an indication of functional protogeny in the Indian damselfish ( Dascyllus carneus ). Journal of Zoology 260(1):23-40.
2. Cohen, P.J. and D.A. Ritz. 2003. Role of kairomones in feeding interactions between seahorses and mysids. Journal of the Marine Biological Association of the U.K. 83(3):633-638.
3. Cote, I.M. and P.P. Molloy. 2003. Temporal variation in cleanerfish and client behaviour: Does it reflect ectoparasite availability? Ethology 14:487-500.
4. Harding, JA., Almany, G.R., Houch, L.D. and M.A. Hixon. 2003. Experimental analysis of monogamy in the Caribbean cleaner goby, Gobiosoma evelynae. Animal Behaviour 65(5):865-874.
5. Hilder, M.L. amnd N.W. Pankhurst. 2003. Evidence that temperature change cues reproductive development in the spiny damselfish Acanthochromis polycanthus. Environmental Biology of Fishes 66(2):187-196.
6. Leis, J.M. and B.M. Caron-Ewart. 2003. Orientation of pelagic larvae of coral- reef fishes in the ocean. Marine Ecology Progressive Series 252:239-254.
7. Payne, A.G., Smith, C. and A.C. Campbell. 2003. Interactions between ophiuroids and beaugregory damselfish. Journal of the Marine Biological Association of the U.K. 83(3):625-632.
8. Southall, E.J., Merrett, D.A. and S. Saunders. 2003. Effects of zooplankton density and diel period on surface-swimming duration of basking sharks. Journal of the Marine Biological Association of the U.K. 83(3):643-446.
9. Trotter, A.J., Pankhurst, P.M., Morehead, D.T. and S.C. Battaglene. 2003. Effects of temperature on initial swim bladder inflation and related development in cultured striped trumpeter ( Latris lineata ) larvae. Aquaculture 221(104):141-156.
10. Trotter, A.J., Battaglene, S.C. and P.M. Pankhurst. 2003. Effects of photoperiod and light intensity on initial swim bladder inflation, growth and post-inflation viability in cultured striped trumpeter ( Latris lineata ) larvae. Aquacultre 224(1-4):141-158.

General

1. Nash, R. and B.F. Keegon. 2003. Aspects of the feeding biology of the fanworm Bispira volutacornis (Polychaete: Sabellidae). Journal of the Marine Biological Association of the U.K. 83(3):453-456.
2. Shine, R., Coggers, H.G., Reed, R.R., Shetty, S. and X. Bonnet. 2003. Aquatic and terrestrial locomotor speeds of amphibious sea-snakes (Serpentes, Laticaudidae). Journal of Zoology 259(3):261-268.
3. Smith, A.M. 2002. The structure and function of adhesive gels from invertebrates. Integrative and Comparative Biology 46(6):1164-1171.

Giant Clams

1. Hean, R.L. and O.J. Cacho. 2003. A growth model for giant clams Tridacna crocea and T. derasa. Ecological Modeling 163(1-2):87-100.

Nutrition

Aquaculture Volume 225 Nos.1-4 (one issue), July, 14th, 2003

This special issue of the journal Aquaculture, contains 37 published papers on fish nutrition that were presented at the 10th International Symposium on Nutrition and Feeding in Fish, held in June 2002 on the Greek island of Rhodes. Papers are divided into the following categories: Feedstuff/Diet Evaluation, Lipids and Fatty Acids, Vitamins and Minerals, and Larval Nutrition. The 37 published papers represent those of most interest to the participants; there were over 250 papers presented.

1. Castell, J., Blair, T., neil, S., Hawes, K., Mercer, S., Reid, J., Young Lai, W., Gullison, B., Dhert, P. and P. Sorgeloos. 2003. The effect of different HUFA enrichment emulsions on the nutritional value of rotifers fed to larval haddock Metamogrammus aeglefinius. Aquaculture International 11(1-2):109-118.
2. Mitra, G. amd P.K. Mukhopadhyay. 2003. Dietary essentiality of ascorbic acid in rohu larvae: Quantification with ascorbic acid enriched zooplankton. Aquaculture International 11(1-2):81-94.
3. Monroig, O., Navarro, J.C., Amat, I., Gonzalez, P., Amat, F. and F. Hontoria.
4. Enrichment of Artemia nauplii in PUFA, phospholipids and water-soluble nutrients using liposomes. Aquaculture International 11(1-2):151-162.

Seagrasses

1. Duffy, J.E., Richardson, J.P. and E.A. Convel. 2003. Grazer diversity effects on ecosystem function in seagrass beds. Ecology Letters 6(7).637-646.
2. Heck, K.L., Hays, G. and R.J. Orth. 2003. Critical evaluation of the nursery role hypothesis for seagrass meadows. Marine Ecology Progressive Series 253:123-136.