Effects of stocking density on behaviour and roe yield in kelp-fed green sea urchins (Strongylocentrotus droebachiensis) farmed in a custom-made raceway

绿海胆（strongylocentrrotus droebacachiensis）的密度高达500只m-2，是圣劳伦斯湾（NGSL）北部浅层岩石潮下栖息地的主要食草动物。绿色海胆渔业完全依赖于人工捕捞海胆个体，目前在NGSL的几个地点正在运作。然而，成功是有限的，主要是因为时间短，即在秋季和冬季的几周内，必须收集海胆性腺或“卵”（海胆的器官出售给人类食用），以尽量减少数量和质量的变化。这种渔业主要针对海胆放牧前沿，在贫瘠的土地上留下高密度的营养不良的海胆，如果这些海胆在陆地设施中使用合适的设备养殖，可以形成可行的商业开发的基础。Pêcheries Shipek S.E.C. （PSSEC）是主要海洋鱼类和贝类商业捕捞的领导者，需要了解定制的滚道（连续流动海水的槽系统）的适用性，以便快速生产大量的绿海胆卵。在这个项目中，我们将研究海胆放养密度如何影响海胆聚集、摄食和海胆卵产量，作为确定海胆饲养海带是否能够支持稳定的商业海胆卵生产的第一步。每周的试验将在12周内进行，在此期间，将定期拍摄海胆和海带的多个部分，并从视频中量化死亡率，海带消耗的数量和聚集程度。在实验开始和结束时，将对海胆的卵黄含量（生长激素指数）进行量化，以确定与放养密度和聚集程度的关系。该公司将利用这一新的行业合作所产生的信息，研究向鱼贩提供多样化鱼种的可能性，同时将自己的部分产品直接出口到区域和全球海胆籽市场。

With densities of up to 500 individuals m-2, the green sea urchin, Strongylocentrotus droebachiensis, is adominant grazer in shallow rocky subtidal habitats in the northern Gulf of St. Lawrence (NGSL). A green seaurchin fishery entirely dependent on harvesting individual urchins manually is currently in operation at severalsites in the NGSL. However, success is limited mainly because of the small period, i.e. a few weeks in fall andwinter, during which urchin gonad or "roe" (the urchin's organ marketed for human consumption) must becollected to minimize variability in quantity and quality. This fishery mainly targets urchin grazing fronts,leaving in the barrens high densities of undernourished urchins that could form the basis of a viablecommercial exploitation if these urchins were farmed with the right equipment in land-based facilities.Pêcheries Shipek S.E.C. (PSSEC), a leader in commercial harvesting of key marine fish and shellfish species inQuébec, needs knowledge on the suitability of a custom-made raceway (system of troughs with continuouslyrunning seawater) for quick production of high volumes of green sea urchin roe. In this project, we willexamine how urchin stocking density affects urchin aggregation, feeding, and roe yield in the raceway as a firststep to determining if the raceway can support steady commercial roe production in green sea urchins fed kelp.Weekly trials will be carried out over 12 weeks during which urchins and kelp in multiple sections of theraceway will be filmed at regular intervals and mortality, amount of kelp consumed, and degree of aggregationquantified from the videos. Roe content (somatogonadic index) will be quantified from urchins at the onset andend of the experiment to determine relationship to stocking density and degree of aggregation. Informationgenerated from this new industry collaboration will be used by the company to examine the possibility ofdiversifying the range of species it provides to fishmongers, while exporting a part of its own productiondirectly to regional and global urchin roe markets.