Scallop growth trial update - October 2013

On Oct 30, 2013 Chris Vonderweidt (ME DMR) and I visited Kevin Scott at the Salt Pond site, and Marsden in Stonington. With us were Bill Trotter and Gabor Degre of the Bangor Daily News; they took a bunch of photos/video and Bill put together a nice piece from the day, viewable at:

http://bangordailynews.com/slideshow/cages-in-maine-pilot-program-could-be-first-step-toward-farmed-scallops/

Scallops continue to do well at both sites, and we still see effects of density happening too: there is a lot of growth sideways (Shell Width) and the shells are standing taller too (Shell Depth).  We have started to collect a little data on the Shell Height/Shell Width ratio to capture this, but there's not much to report on there yet.  Attached is a graph that summarizes growth at the three sites over time. This might be useful as we home in on the right times of year to do thinning: looking for the times when the growth curve starts to deflect downward. On the other hand, we've handled scallops more frequently that would likely occur in a production setting, and to that end, I could see how our growth might be slower, because of the added handling stress.

At Marsden's site, the Aquatrays got nailed with a pretty decent barnacle set, including the scallops inside the cages, though the shellfish bags seemed to avoid this more or less...unclear as to why that was.  Mortality at both sites was near zero.

As you'll see from the chart below, I made an error in restocking the low-density cages out in Stonington, so that will throw results off a bit, but at least we know about it....the density should have been lower.

Roe development was pretty good at both sites; it seemed that in Blue Hill there was less resorption or spawning - gonads seemed fuller, but still decent at both sites.  Bummed that I didn't get any good shots of this, but Bill Trotter also has a Tumblr site, and there are some shots there..

http://billtrotter.tumblr.com/

Shell Heights and growth rates:

                                 BlueHillLOW   BlueHillHIGH   StonLOW  StonHIGH
Prior average (mm)   52.1                 49.3                    64.43          56.1
Current Average        67.48               60.83                  70.59          62.1
#days                        180                   180                     98               98
Difference                 15.38               11.53                  6.16            6.0
growth/day (mm)      0.0854             0.0641                0.0629        0.0612
prior stocking            47                    94                       24               80
current stocking        24                    66                       29               60


Biotoxin samples were taken from both sites.  So far, all samples tested have been clean for PSP, more data to come on presence/absence of DSP and ASP. 

This is the growth since first cages were stocked in 2012. You can see the effect of site, and the differences between the low-density group (30% bottom coverage) and the high-density group (60% bottom coverage)

Here's a nice set of scallops from the Blue Hill Salt Pond site (Evan Young and Kevin Scott); smooth shells indicate low stress.

Two year classes on the Sand Island site (Marsden Brewer); the difference in shell size is due to one year's growth. Pretty encouraging.