Dataset: urchin_algal cover

For complete information, see the final report.

Site evaluation:
During April 6th to 11th, 2009, shortly after the annual fishing season had closed, all sites were marked and evaluated for urchin abundance and algal cover

Harvest treatments:
Treatments were designated A=straight raking (non-size-selective), B=size-selective fishing (bottom culling), and C=control (unfished). The lane arrangements ABC, CAB, and BCA (left to right when looking at the lanes from the sea toward shore - see figure in final report for the ABC arrangement) were randomly assigned to the three experimental sites, which turned out to be Hancock Point, Winter Harbor, and Frazer Point respectively.

The harvest treatments were applied April 15 (Winter Harbor) and April 16 (Hancock Point and Frazer Point), 2009. At the size-selective plots (B), one of the two industry divers (Marcus) began at the deep end of the lane and made his way to shore, harvesting mostly only the legalsized sea urchins, using the techniques of size-selective divers. At the non-selective plots (A), the other industry diver (Greg) harvested all sea urchins that a straight-raker would take. That is, clumps of urchins that all appeared too small were passed over, but groups that contained at least one urchin that might be legal were entirely harvested. The third plot (C) at each site was untouched. The divers were video-taped to document the two fishing styles. Standard 2¼-inch stretch mesh catch bags were used throughout.

Counting, Measuring, and Replanting:
Harvested urchins were picked up by the fishing vessel (a 38-ft lobster-type boat with only 3.5 ft draft). On the vessel, all harvested urchins were separated by treatment and size (sub-legal, legal, over-sized), counted, and put in 80-lb (36 kg) plastic fish totes. The determination of size was made by an experienced commercial sea urchin culler. Test diameters were also measured for forty urchins chosen at random from each tote. The totes were only filled to about two-thirds full (about 50-60 lbs) to minimize crushing and spine puncture, and periodically hosed with sea water.

When harvesting was finished each day, sub-legal and over-sized urchins were moved to the replanting site at Bean Island Ledge and dropped onto it from the surface, over the ground line between the two marker buoys. The replanted sea urchins had been out of the water about 6-7 hours at most. Legal-sized urchins were returned to the sea at an undisclosed site well away from any of the experimental sites.

Post-harvest site evaluations in April, 2009:
After harvest (later the same day), the harvested plots were re-evaluated for urchin density as above. The replanted site was also re-evaluated for urchin density as above at the end of the second day of replanting (April 16, 2009).

On April 24, a little over a week after translocating, the replanted site (Bean Island Ledge) was evaluated for urchin density, and for urchin mortality by counting healthy-appearing urchins and moribund or broken ones in 60 random quadrats.

After re-evaluation, the groundlines were removed from each site.

Re-evaluations in July, 2009:
On July 1, 2009, the two industry divers re-evaluated the harvest and control lanes at the Winter Harbor and Frazer Point sites, using the same methods described above, except that no urchins were collected for measurement. First, ground lines were laid to mark the three lanes at each site, using buoyed anchors and bolts left behind during the last visit. On July 2, they marked and re-evaluated the harvest and control lanes at the Hancock Point site and the replanted and control areas at Bean Island. Then the ground lines were removed from all sites. A total of 11 dives were made by each of the two divers during this period (three at each of the three harvest sites and two at the transplant site), and each diver evaluated 30 quadrats during each dive, for a grand total of 660 quadrats evaluated for urchin counts and algal cover, including about 66 from which urchins were removed and measured on the boat.

Re-evaluations in September, 2009:
On September 1 and 2, 2009, just before the fishing season opened, the four sites were marked and evaluated in the same manner again, including collecting urchins for measurement. All lanes at all the sites were also videotaped under water. Then the ground lines were removed from all sites.

Re-evaluations in June, 2010:
On June 29 and 30, 2010, after the fishing season had closed, the four sites were marked, evaluated, and videotaped in the same manner again. Then the ground lines were removed for the last time.