The following questions were posed by Dr. Parrish on 8/3/02 and my response is as follows.

1. What ‘evolutionary’ question if any , will this work answer? How?

It is difficult to ask evolutionary questions because of the difficulty of proving anything. My experiment will not tempt to solve the evolution of the shimp-goby relationship. Instead it may answer a part of the question. It has been hypothesized that shimp-gobies may have evolved in response to predation (Karplus 1987). Yet, no one knows for sure the exact effect of predators on the population. Thus, this study will attempt to fill this very important void in the literature by showing the effect of predators in the short term. It will not be able to make any assumptions of natural selection, because the population is an open population and cannot be tracked over time.

2. “Equalization” – How long does it take for migration and recruitment to bring a newly fenced area to a “normal”, stable population / distribution of shrimp and goby in a cage?

Gobies are small, relatively short-lived creatures. Their life expectancy is quite low. According to Dr. Greenfield, these gobies may be lunar, but a better bet is that they are breading every few days. He thinks they probably only live a year and with the size variation in the bay, I too assume they are breeding at least every month if not more often.

3. Do you want to add predators to a full cage (or at least to know how many are confined in it (and compare with “natural” numbers from census?)

This is a good question. It can be ascertained by adding predators to the cages after the initial study is completed, if there is no effect of predators. I would say that I should do this as a second alternative to the study however, as capturing these predators to toss in the cage would prove very difficult. In addition, I am not yet sure which animals are the main predators.

4. Do you want to be sure to exclude all predators from a full cage?

It will be impossible to exclude ALL predators in the cages as there are lizardfish that are exactly the same size as gobies swimming around. The fish I plan on excluding will be the large roaming predators seen in the bay including goatfish, hammerhead sharks, and jacks. This should also exclude eels over 1 inch in diameter.

5. How much difference do you expect in left, middle and right in gobies, based on observations, density census to date?

I do expect some difference in the density as the shrimp do not seem to be able to dig in sediment that lacks some sort of underground structure. In this case a base of coral rubble constitutes a significant enough base to allow the shrimp maintain the holes. Farther out in the bay where wave action is higher and the sediment lacking coral rubble I found almost no shrimp gobies.

6. Replicates will be important, maybe more so than looking for a spatial difference. In left, middle, and right will I find a difference with only 6 cages (ie. 3 areas each with 2 configurations – full and ¾ = 6) There is no replication. With left, middle and right considered 1 area, there are 3 replicates (2 configs x 3 reps).

As such I believe the best solution is to confine the cages to the right side (now considered the north side of goby bay). It will decrease some of the variability and make the difference easier to distinguish.

7. Separate (for committee) – 1) what work is done and what conclusions come from it, and 2) What work is still to be done.

See Introduction

8. If we do have 2 shrimp species, how well can you differentiate them in the field?

There are two shrimp species that Lynn Moehring found in the bay when she did her dissertation (Alpheus rapax and A. rapicida) (which by the way was based on 3 holes where she happened to come across one). However, I have not been able to see any distinct difference in the two species while taking field observations. For the study however, it does not seem to matter if I identify the shrimp to species.

9. Specifically ID each cage as to size, construction (open / closed), location, contents (fish, gobies), treatment (adding pred, removing pred), duration, data taken.

See cage schedule

10. How are cages “altered”? Caged between full <-> ¾? Is ther a good idea? If anything, always go none à ¾ à full.

This is a good point. To combat this situation I will be measuring the difference between going from ¾ to full and back again a few times. I will also compare these transitions between months to the normal transition of my control plots. Hopefully this will eliminate any bias.

11. What species and sizes do you think are likely predators, and how will you exclude them (e.g. what mesh size?) What potential predators may not be excluded?

I assume that likely predators are lizardfish (present in the bay. Large ones will be excluded but small ones which are the same size as gobies in the bay will not be excluded), goatfish (mostly over 6 inches that school in the channel to the north), hammerhead sharks (seen in the bay on 2 occasions) and stomatopods (Ken Longenecker suggests that they may be a major predator on the reefs, yet I have never seen one in the bay and they will not be excluded – I also put a 2 inch stomatopod (Gonadactylaceus mutates) into my tank for a year with 5 gobies but had no goby fatalities)).

As a total hunch, I imagine that the largest risk of predation is from roving predators such as the goatfish and sharks that (while not likely to be encountered by a snorkler probably roam the bay frequently looking for creatures in the sand.