Cuticular lesions from twenty-four market sized lobsters (Homarus americanus) with winter impoundment shell disease were examined. Histological descriptions of cuticular lesions were correlated with the substage of molt for each lobster, because cuticle components and inflammatory mechanisms vary in each. A lesion severity grading system was developed and applied to four specific substages of the five-stage (A-E) molting cycle. Lesions present in substage C4, in which the membranous layer is deposited, and D0 (passive premolt) were divided into five grades, ranging from mild erosions (Grade I) to severe ulceration (Grade V) of the cuticle. Cuticular lesions from lobsters in C4/D0 were compared with cuticular lesions from lobsters in substages C2/C3. Defensive mechanisms exhibited by animals in all substages were epicuticle deposition, melanization, inflammatory cell infiltration, and pseudomembrane formation. In addition, animals in C4 and D0 showed proliferation of the membranous layer in affected foci. The lesion grading scheme presented in this paper can be used to describe and compare both inter- and intraspecies crustacean shell lesions.

Reduction or elimination of fish meal and fish oil from aquaculture diets can help to reduce the potential for contamination and dependence of the industry on pelagic fisheries while improving economic competitiveness. However, fish oil provides important omega‐3 (n‐3) fatty acids (FAs) essential to shrimp health and beneficial to humans. This study evaluated an organic, plant‐based diet formulated to replace fish meal and fish oil with plant proteins and docosahexaenoic acid (DHA) produced by algal fermentation. Shrimp cultured in replicate outdoor ponds at 25/m2 were fed either a diet composed of organically produced plant ingredients or a conventional commercial fish‐meal‐based feed. No significant differences were found in production parameters between the conventional fish‐meal‐based diet and the plant‐based diet (production: 4594 and 4592  kg/ha; harvest size: 18.7 and 19.2  g; survival: 93 and 88%; and feed conversion ratio: 1.4 and 1.3, respectively). At harvest, shrimp were analyzed for 147 chemical contaminants and 71 FAs. Contaminant levels were negligible for shrimp raised on both diets. The fish meal and fish oil diet provided significantly higher quantities of eicosapentaenoic acid and DHA than the plant‐based diet, and the shrimp fed the conventional diet reflected this with higher levels of these beneficial FAs in edible tissues. Differences between feeds and shrimp tissues suggest that essential n‐3 FAs may accumulate in shrimp tissues over time or that natural pond productivity may play a role in providing supplemental nutrition. Shrimp raised on the two diets and wild‐caught shrimp are clearly distinguishable by their FA profiles. Compared to alternative protein sources like beef, pork, or chicken, differences in lipid profiles of shrimp raised on either diet may be insignificant because both offer increased human health benefits.

A 15‐week growth trial was conducted with juvenile, Pacific white shrimp Litopenaeus vannamei to study the efficacy of using algal meals as a source of highly unsaturated fatty acids in practical diets that are designed to contain no marine protein or oil sources. Based on previous study, a practical diet was designed containing co‐extruded soybean poultry by‐product meal with egg supplement and soybean meal as the primary protein sources for formulations containing 350 g kg−1 crude protein and 100 g kg−1 lipid. To further refine the diets, the fish oil in two of the diets was completely substituted with plant oils and oil originating from microbial fermentation products rich in docosahexanoic acid (DHA) and arachidonic acid (ArA). A commercial shrimp feed was also included in the trial for comparison. The mean values for shrimp final weight (17.8 g), yield (537.7 g m−2 or 703.2 g m−3), survival (98.5%) and feed conversion ratio (1.4 : 1) showed no statistically significant differences between diets. The results suggest that co‐extruded soybean poultry by‐product meal and oil from heterotrophic microalgal fermentation sources can be potential candidates for fish meal and marine oil replacement in shrimp diets.

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