| Adrian Jordaan | |
School of Marine Sciences, 214 Libby Hall, University of Maine, Orono, ME, 04473
Graduated with a BSc (honors) from Memorial University of Newfoundland in 1999.
Currently enrolled in a MSc. degree in Marine Biology
Research summary
I strongly believe in the importance of information sharing between aquaculture and fisheries research. I have been invloved in a collaboration of researchers studying processes on Georges bank. Please read on and feel free to contact me with questions and comments.
It has generally been believed that the Northeast Channel and current patterns at the Scotian Shelf/Georges bank margin do not allow for mixing of the populations of cod from the two regions. Georges bank cod spawn from January through June with eggs being released on the Northeast corner of Georges Bank and moving around the bank in a clockwise pattern. Due to the Coriolis effect, water moving south from the Scotian shelf tends to be pulled around the tip of Nova Scotia and up into the Bay of Fundy. Recently, it has been discovered that large scale fluxes of cold (2ºC), fresher water (30‰) from the Scotian shelf are crossing over the Northeast channel and are being incorporated into the Georges Bank circulation pattern. More importantly, this water contains significant numbers of cod eggs, indicating that perhaps some Georges bank cod originate from Canadian waters. The goal of this project was to correlate strontium-calcium ratios (Sr/Ca) to the temperature history of laboratory reared cod larvae and use the information to infer the temperature history of larvae collected on Georges bank and the Scotian shelf. With this information, the relative contribution from both the Scotian shelf and Georges bank to the Georges bank population of cod could be estimated and a better understanding of the interaction of the two water masses could be realized.
Unfortunately, thus far the elemental analysis of otoliths extracted from the laboratory-reared cod larvae has not revealed any temperature-Sr/Ca relationship. However, two important conclusions have resulted from the funding of the project. The first relates to the relationship at the time of hatch among temperature and larval size, development stage, the ability to begin feeding. Published literature currently suggests a dome-shaped relationship between size of hatching larvae and the egg incubation temperature (Galloway et al, 1999; Pepin et al, 1997). This is viewed as significant because subtle differences in sizes of larvae are believed to impart large differences in survival probability (Miller et al, 1998). The differences in size are hypothesized to originate through metabolic mechanisms; smaller larvae may have deficiencies in metabolic processes during development which cause less energy to be transferred from the yolk-supply to growth (Pepin et al, 1997). This research, completed in concert with the rearing of larvae for the otolith analysis, refutes these ideas and instead shows that most of the differences in size result from differences in the development stage at hatch (smaller larvae are earlier in development). The incubation temperature also affected the ability of larvae to initiate feeding as yolk-sac resources were depleted. Larvae from the extreme temperatures (2 and 12°C) had developmental abnormalities that effectively caused a large percentage of the larvae to not feed and ultimately to starve. For a look at pictures and a description of the staging table used in my research see the biology page at this website, then scroll down until you see hatching larvae.
The second major conclusion involves the effect of temperature on efficiency of growth. After larvae began to feed, clear differences in the growth rates among temperatures emerged. Two processes are important in changing growth rates with temperature in poikilothermic organisms such as fish. First, increasing temperature influences the rates of chemical reactions. Second, at temperature extremes energy transfer from prey capture to growth suffers reduced efficiency. The reduced efficiency is the result of metabolic processes (enzyme kinetics) and bio-physical interactions at small sizes and cold temperatures (see Fuiman & Batty, 1997). The two processes result in a bell-shaped growth curve which approximates a log-normal relationship over the thermal range of a species (Jobling, 1993). Often the temperature of maximum growth is cited as the optimal temperature for fish (see Steinarsson & Björnsson,1999). The data from this research suggest that, in reality, a point at a lower temperature than the temperature of maximum growth rate is the point of the most efficient transfer of energy.
Results from the temperature study described herein will likely help direct future research on gadid larvae and the interaction between Scotian shelf and Georges bank water. Improved understanding in these areas will benefit fisheries science by allowing possible modeling of across-stock interactions and the influence of temperature on larval recruitment.
Other Projects
I also am involved as a field leader on a survey of tidepool and estuary fishes in Acadia National Park. We have been gathering data on the presence of fish species and physical and biological parameters of the sample sites. We are hoping to correlate microhabitats and fish species, eventually developing models that could be used to predict fish presence. These could be used by the park to monitor the health of tidepools aroung the island.
I was responsible for much of the website you see.
I have also been working with Dr. Yong Chen on a review of biological reference points.
Publications
Jordaan, A. 1998. Age-specific starvation in larval Atlantic cod (Gadus morhua L.). Honours Thesis, Memorial University of Newfoundland.
Jordaan, A. & J.A. Brown. Age-specific vulnerability to starvation of larval Atlantic cod (Gadus morhua L.). Submitted to the Canadian Journal of Fisheries and Aquatic Sciences.
Callan, C., Jordaan, A. & L.J. Kling. Reducing Artemia use in the culture of larval Atlantic cod (Gadus morhua). Submitted to Aquaculture.
Conferences
Jordaan*, A. & J.A. Brown 1998. Age specific vulnerability to starvation of larval Atlantic cod (Gadus morhua L.). 29th Annual Atlantic Universities Undergraduate Conference Programme. Halifax, Canada. (Poster presentation)
Jordaan*, A. & L.J. Kling 2001. Temperature induced changes of early life-history traits in Atlantic cod (Gadus morhua). Canadian Conference for Fisheries Research. Toronto, Canada. (Poster presentation)
Jordaan*, A., Callan., C & L.J. Kling 2001. Reducing Artemia use in the culture of larval marine fish: an experiment using Atlantic cod (Gadus morhua). Aquaculture Association of Canada Annual Meeting. Halifax, Canada. (Oral presentation).
Hayhurst*, S. & A. Jordaan 2001. Just say no to backbones: Invertebrate zoology as a hands on tool for biology education. 9th International Congress on Invertebrate Development and Reproduction. Grahamstown, South Africa. (Poster presentation)
Jordaan*, A., Hayhurst, S. & Linda J. Kling. 2001. The effect of temperature on early life-history traits of Atlantic cod (Gadus morhua) larvae. 25th Annual Larval Fish Conference. Sandy Hook, NJ, United States. (Oral presentation)
Jordaan*, A., Hayhurst, S. & Linda J. Kling. 2002. The consequences of temperature change for developing cod (Gadus morhua) larvae. Canadian Conference for Fisheries Research. Vancouver, Canada. (Poster presentation)