Evolving cage design for floating oyster farms in Barnegat Bay, NJ

Evolving cage design for floating oyster farms in Barnegat Bay, NJ

Summary

Site-specific farming impediments in Northern Barnegat Bay require the development of customized gear that addresses these issues. Depths over 8 feet require work to be conducted onboard skiffs instead of in shallow water, common elsewhere in the state; the approved growing area lacks the hard sandy bottom commonly used for cultivation, causing equipment to sink deep in silt, degrading oyster health and marketability; winter freezing and strong storms make surface gear vulnerable if left floating year round. Additionally, current gear is too cumbersome for many of the baymen and women cultivating oysters at the site.

The purpose of this study was to improve growing methods by testing 2 experimental cage designs and compare results to the system currently (and most commonly) used on floating farms, the OysterGro™ system. The first experimental design is the OysterGro Mini™ system, similar to the OysterGro™ but with smaller floats and 1/3 less capacity, changing buoyancy, balance, and general handling, among other important differences. The second experimental design is the LowGrowPro™ prototype, developed by Ketcham Traps in New Bedford, MA. The LowGrowPro™ was developed as a possible lightweight solution for farmers with similar growing conditions as ours and consists of removable foam floats and 1/6^th the capacity of the OysterGro™ system.

Update: Our original proposal stated criteria for the design of a second experimental cage, to be created for the study. During our pre-study preparation period, we discovered a prototype being produced by Ketcham Traps in New Bedford, MA, that fit our design requirements. This prototype, the LowGrowPro, was used in place of the design stated in our original proposal.

Our technical advisor, Gef Flimlin was instrumental in the design of our grant proposal and assisted in the creation of the data collection performance indicators.

Objectives/Performance Targets

Our study consisted of 4 phases, beginning with obtaining of gear, followed by the planting and deployment of gear and oyster seed, followed by the maintenance of gear and data collection, and finally, analysis of data collected for final results and outreach.

Phase 1: Obtain Gear

During this phase, we acquired a cage kit to build 4 OysterGro Mini™ cages and the LowGrowPro cages from Ketcham Traps (www.lobstering.com). For comparison, we used 4 of our OysterGro™ cages, already acquired from Ketcham Traps.

Phase 2: Planting and Deployment of Gear

During this phase, we planted ½”, disease-resistant seed stock into 4 cages of each of the 3 designs mentioned above, for a total of 12 experimental cages. Four longlines were selected at random within our leasing area where 1 of each of the three cage designs was placed in a cluster and remained for the study period.

Phase 3: Maintenance of Gear and Data Collection

During this phase, data collection occurred on 7 different indicators and 2 different collection schedules. Data indicators included the following:

1. Ease of flipping (EF), determined by farming crew and rated on a 1-5 scale.
2. Ease of sinking (ES), determined by farming crew and rated on a 1-5 scale.
3. Ease of re-floating (ER), determined by farming crew on a 1-5 scale.
4. Ease of general handling (GH), determined by farming crew while maintaining gear on a 1-5 scale.
5. Silt-sinking depth (SS), determined by measuring distance cages sank in silt at different lengths of time existing on bottom, measured in centimeters.
6. Oyster Growth (OG), measured in average shell height centimeters.
7. Gear Fouling (GF), measured by farming crew on a 1-5 scale.

Data Collection Schedules were performed as follows:

Schedule 1: Ease of flipping (EF), general handling (GH), oyster growth (OG), and gear fouling (GF) were measured weekly during general farm maintenance for 4 months, from July through October. Farm crew worked through longlines, and when experimental cages were encountered, data was collected using appropriate scales and data tables.

Schedule 2: Data collection for indicators Ease of sinking (ES), ease of re-floating (ER), and silt sinking depth (SS) began in early November, after Schedule 1 was completed and after water temperatures dropped below 50°F. Day 1 consisted of sinking all cages for the winter season. Farm crew rated experimental cages ease of sinking (ES) using ES Data Table. Ease of re-floating (ER) and silt sinking depth (SS) were measured every 2 weeks for 4 cycles through the middle of December. Cages were lifted using our davit crane, drained of water in pontoon floats/replacing foam, and rated using the ER Data Table. In addition, silt-sinking depth was determined by measuring silt residue left on cages and recorded using SS Data Table (however, SS data was inconclusive).

Phase 4: Analysis of Data and Outreach – Yet to be completed

During this phase, data will be compiled and analyzed for conclusions. The results of each cage’s performance for each indicator will be compared. The final report will be drafted and published indicating findings for use in the local industry. Outreach will begin through the Northeast Aquaculture Conference and Expo (NACE) or Milford Aquaculture Seminar, East Coast Shellfish Growers Association, RCE, and/or to our neighboring growers at Swan Point.

Accomplishments/Milestones

1. Growth of oysters during the early part of the study showed no significant difference between cage systems – oysters seemed to be growing at about the same rate. Towards the end of the study period, the LowGrowPro™ oysters had outpaced both OysterGro™ products by over 50%.
2. As expected, Ease of Flipping (EF) and General Handling (GH) scores for the OysterGro™ system were the lowest while the LowProGrow™ design scored the highest, an obvious prediction based on size, shape, and mass – however, the OysterGro Mini™ design scored almost as low as it’s full-sized cousin, despite it being 33% smaller and less capacity.
3. After about a month, fouling began to become evident on each of the three systems, with the LowGrowPro™ suffering from the lowest fouling scores (most biofouling).
4. Ease of Sinking (ES) indicators didn’t seem to have a significant difference between systems, while Ease of Re-floating (ER) scores for the LowProGro™ system were far higher and didn’t even require the davit crane to resurface.
5. Silt-Sinking (SS) indicator, as measured at time of writing, was inconclusive. Silt residue that was intended as a marker of the depth cages sank below the soft bottom was too difficult to measure accurately. Perhaps a more accurate reading will be observable during the spring resurfacing of gear.

* The above observations represent a snapshot of data as collected during the study period. A full analysis of data has yet to be completed and our technical advisor, Gef Flimlin of Rutgers University has yet to review the study.

Collaborators: