Summary of Trips

One dive trip was made during the fiscal month of May. Its purpose was to make observations of some of the Modules that were sunk last November to determine their effectiveness as fish havens. In particular, visits were made to an isolated busted up module and to part of a chain of 12 grouped modules. The idea was to compare the effectiveness of grouping the modules rather than isolating and also the effect of busting them up rather than sinking them whole.

During the past month about sixty fish were tagged and released. Seven previously tagged fish were recaptured.

Modules 53 & 54

These modules busted up as they went down in the west end of the Horn Island Barge site (FH-1) between the Rubble Barge (Barge "E") and Rubble Pile #1. The LORAN coordinates are 12404.0, 47037.4 (.3), 29572.9 (.8). These coordinates are about a tenth of a microsecond off the ones reported from the spotting operations. The material is somewhat small in area and somewhat isolated from other material. This made it a good control site to determine the advantages of busted up low relief concrete as opposed to using a whole module.

This site showed many more smaller fish in much larger quantities when compared to the whole module observed last month. Also schools of Cigar Minnows, small crabs and sea urchins were seen. The Red Snapper that were captured and tagged topside also averaged 2"-3" smaller although one warsaw grouper was caught that measured 17.5". The general game fish sighted during the dive are summarized below in Table One.

Fish Sightings on Modules 53 & 54

June 10, 1990

Fish Type Size/Weight Count

Red Snapper.......... <1 lbs....50-75

Trigger Fish......... <1 lbs.... 3

Grouper.............. 1-3 lbs.... 3

Cobia................15-20lbs.... 1

Spanish Mackerel..... 1-2 lbs....25-50

Table One

Modules 72-83

The last twelve modules sunk during the project were grouped together in the southeast corner of the Bill Walker site (FH-2). The approximate center of this area was visited to make comparisons with the isolated modules already visited. The LORAN coordinates of the visit were 12444.1-.3, 47043.1-.2. There were two modules found here. One had a roof and one did not. There was also some broken debris and slabs in the area. There were numerous fish sightings, both juvenile and game size. The area exhibited qualities of both the whole and broken up module sites already visited. It was interesting to see that few fish favored the module with the roof on it, however, they swam freely in and out of the open top module. Some fish made burrows under the modules as well as under the slabs, including a 3-4 pound flounder. The sightings are summarized below in Table Two.

Fish Sightings on Modules 74 & 79

June 10, 1990

Fish Type Size/Weight Count

Spade Fish........... 6-8".......35-50

Trigger Fish......... 1-3 lbs....30-40

Red Snapper.......... 1-3 lbs....60-80

Red Snapper.......... <1 lbs....50-75

Sheepshead........... 1-3 lbs....10-15

Flounder............. 3-4 lbs.... 1

Spanish Mackerel..... 1-2 lbs....50-75

Table Two

Conclusions

Evidence between last month and this month dictate that the broken up pieces of concrete are much more effective as fish havens than whole smooth pieces. They do, however, need more time to develop since they attract many more juveniles and bait fish.

A roof top over the habitat severely hampers the reef, even if it has many openings and is open completely on one end. This may explain why the railroad box cars have not done as well as expected. If the top is open to the water, then the open doorways and windows appear to be an additional asset.

The grouping of the modules in the southeast corner of the Bill Walker site appears beneficial. Since some pieces are broken up it exhibits qualities of both types of reef. They fact that the reef is a little scattered may contribute as well. Further surveys are needed to pinpoint the condition and location of the other ten modules in relation to these two.

Fish Tagging Update

Last month approximately 60 new fish were tagged and released and seven tagged Red Snapper were recaptured. Two recaptures came from outside the organization, but with no useful information. One tag's information is pending arrival from Texas. The other four are listed below in Table Three. The "Rate/Mo." figure is the computed growth rate per month. All these Snapper were recaught on the same structure that they were tagged on.

Tagged Fish Recaptures

(for past month of May)

Tag Number Date-1 Date-2 Size-1 Size-2 Growth Rate/Mo.

49471 1/14/90 5/06/90 12.00" 12.50" 0.50" 0.13"

49476 1/14/90 5/06/90 9.00" 11.25" 2.25" 0.60"

49490 1/27/90 5/06/90 10.25" 11.50" 1.25" 0.38"

62936 4/15/90 6/10/90 11.00" 13.00" 2.00" 1.07"

Table Three