Predation and Growth of Manila Clams in Geoduck Aquaculture Areas
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The document summarizes a study on the predation and growth of Manila clams in areas used for geoduck aquaculture. The study found higher densities of potential clam predators like starfish and crabs at geoduck farms compared to reference beaches. Survival rates of Manila clams planted in the study were lower in farm plots due to higher predator densities. While growth trends of the clams suggested slower growth in farm plots, the differences were not statistically significant. The conclusions indicate predator densities and subsequent predation on clams are affected by the presence of geoduck farms.
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Predation and Growth of Manila Clams in Geoduck Aquaculture Areas
- 1. Predation and Growth of Manila Clams in Geoduck Aquaculture Areas By Julia Eggers and Hans Hurn
- 13. Photo by Kevin Lee Photo by Peter J. Bryant Photo by Todd Warshaw
- 14. Experiment Two plots per site Reference Farmed
- 18. Predator Density Sea Stars Graceful Crab Flatfish www.dfw.state.or.us/MRP/finfish/images/species/sandsole.jpg
- 20. Clam Survival
- 21. Fisher Rogers Stratford Sig. site<0.001 plot<0.001 enclosure<0.001
- 22. Fisher Rogers Stratford
- 23. Fisher Rogers Stratford Farmed Reference
- 24. Fisher Rogers Stratford Farmed Reference
- 25. Fisher Rogers Stratford Farmed Reference
- 26. Fisher Rogers Stratford Farmed Reference
- 28. Clam Growth
- 30. Fisher Rogers Stratford Farmed Reference
- 34. Acknowledgments Thanks to Sean McDonald for his help designing and carrying out this project, Glenn VanBlaricom, Taylor Shellfish for the clams, the geoduck farmers and all the volunteers that made our work possible!
- 35. Questions?
Editor's Notes
- Farmed sites: predators above and below nets Aggregate for July 50% higher predator density at farmed sites. Very few predators observed under nets at farmed sites. Primarily C. Gracillis
- Fisher inverse relationship in July + August Aggregate 50% more preds at farmed sites
- Farmed sites: predators above and below nets Predator density negatively affects survival at each site Not primary factor as not correlated accross sites
- Farmed sites: predators above and below nets Predator density negatively affects survival at each site Not primary factor as not correlated accross sites
- Farmed sites: predators above and below nets Predator density negatively affects survival at each site Not primary factor as not correlated accross sites
- Farmed sites: predators above and below nets Predator density negatively affects survival at each site Not primary factor as not correlated accross sites
- Talk about larger factors affecting survival site netting
- Growth for control enclosures only Lower growth rates in farmed plots Rogers site predator-exclusion nets removed during experiment 39% faster growth at Fisher and 18% faster growth at Stratford reference plots.
- Growth for control enclosures only Lower growth rates in farmed plots Rogers site predator-exclusion nets removed during experiment 39% faster growth at Fisher and 18% faster growth at Stratford reference plots.
- Farmed sites: predators above and below nets Predator density not correlated with growth
- Farmed sites: predators above and below nets Predator density not correlated with growth
- SHOULD NOT BE SUB-BULLETS GROWTH NOT SIGNIFICANT SO YOU CAN MENTION TREND BUT INDICATE THAT MORE WORK IS NEEDED SURVIVAL OF CLAMS IS LIKELY LINKED TO PREDATOR DENSITY WITHIN EACH SITE BUT YOU CAN’T SAY CORRELATED BECAUSE YOU CAN’T DO A CORRELATION ON TWO POINTS FOR EACH SITE. GROWTH OF CLAMS ISN’T LIKELY TO BE NEGATIVE HERE OR IF IT IS THE TREND IS ALMOST A FLAT LINE. YOU NEED TO HAVE AN IMPLICATIONS SLIDE RELATING THESE RESULTS TO THE LARGER PICTURE OF GEODUCK MANAGEMENT. There are other ways predator exclusion devices can be applied over tubes. How would predator dynamics change with individual nets? How would growth/survival be affected?
- SHOULD NOT BE SUB-BULLETS GROWTH NOT SIGNIFICANT SO YOU CAN MENTION TREND BUT INDICATE THAT MORE WORK IS NEEDED SURVIVAL OF CLAMS IS LIKELY LINKED TO PREDATOR DENSITY WITHIN EACH SITE BUT YOU CAN’T SAY CORRELATED BECAUSE YOU CAN’T DO A CORRELATION ON TWO POINTS FOR EACH SITE. GROWTH OF CLAMS ISN’T LIKELY TO BE NEGATIVE HERE OR IF IT IS THE TREND IS ALMOST A FLAT LINE. YOU NEED TO HAVE AN IMPLICATIONS SLIDE RELATING THESE RESULTS TO THE LARGER PICTURE OF GEODUCK MANAGEMENT. There are other ways predator exclusion devices can be applied over tubes. How would predator dynamics change with individual nets? How would growth/survival be affected?