Every year, large amounts of shrimp waste are disposed of in the environment, causing serious environmental problems. The prospect of recycling shrimp waste helps to reduce waste and protect the environment. In this study, three different shrimp species were used, including Pleoticus muellieri, Litopeneus vanamei, and Parapenaeus longirostris, separated into shells (PLMUS, LIVAS, PALOS) and tails (PLMUT, LIVAT, PALOT), and transformed into novel carbonaceous materials. Their adsorption properties were investigated using different chemical compounds (MB, MR, phenol, astaxanthin) in aqueous means. The materials were characterized through FTIR, BET, and SEM–EDS analyses. According to the results, the carbonaceous adsorbents presented high adsorption percentage of MB and astaxanthin (>90%), and low adsorption percentage of phenol and MR, owing to the different bonds that were formed between the functional groups of the organic substances and the corresponding groups on the surface of the materials. The results of the FTIR analysis show the presence of C=C groups from the aromatic rings of the adsorbed MB and MR at 1636 cm⁻¹, the presence of O-H functional groups from the adsorbed phenols at 3330 cm⁻¹, and the presence of C=C or C=O groups at 1730 cm⁻¹ after the adsorption of astaxanthin. According to the BET analysis, the increase in the specific surface area follows the order: LIVAS > PLMUS > PALOT > PALOS > PLMUT > LIVAT. SEM–EDS analysis presented compact structures with the main elements of C (37–56%), O (25–35%), and Ca (12–23%) for all materials. Kinetic analysis showed that the experimental adsorption data of all the organic substances can be best described by the pseudo-second order model, indicating that chemisorption is the prevailing mechanism. Consequently, such methods promote the sustainable management and zero-waste fish farming practices, fostering the production of high-added value materials not only for decontamination purposes but also for the isolation of bioactive substances.

Valorisation of crab by-products by enzymatic hydrolysis (EH) is proving to be a promising strategy to promote sustainable aquaculture and support a circular economy for crustaceans. Crab processing generates significant amounts of by-products that, if not properly managed, pose an environmental and economic challenge. These by-products are rich in chitin, proteins, and bioactive compounds and offer significant untapped potential for the development of functional feed. This review focuses on the application of enzymatically hydrolysed crab by-products as functional feed additives in aquaculture and their effects on fish growth, health management, and, consequently, human health. Recent studies have shown that EH effectively recovers chitin and bioactive peptides and improves the digestibility and bioavailability of nutrients in aquaculture. The inclusion of crude chitin, along with residual proteins and calcium carbonate, in the diet of farmed fish has been associated with increased growth, improved immune responses, and greater disease resistance, emphasising their critical role in fish health management. In addition, these functional additives contribute to the development of innovative aquafeeds with high added value and improved nutritional quality, while reducing environmental waste. Overall, the utilisation of crustacean by-products through enzymatic hydrolysis represents a valuable tool for the sustainable development of crustacean aquaculture, promotes the circular economy, and supports the development of innovative functional feeds while improving the growth and health of farmed fish, which has a positive impact on human health through their consumption.

The locally isolated harpacticoid copepods Tigriopus sp. and Tisbe holothuriae were subjected to salinity tolerance experimentation at salinities under and above of 40 ppt, and presented high halotolerances in Tigriopus LC50 (24 h) of 1 ± 4.43 ppt and 132 ± 5.35 ppt, respectively, and in Tisbe of 15 ± 2.41 ppt and 93 ± 3.23 ppt, respectively. Tetraselmis suecica, among other microalgal feeds (Asteromonas gracilis, Rhodomonas salina, Dunaliella salina and Isochrysis galbana), resulted in the higher production of nauplii in Tigriopus and R. salina and D. salina in Tisbe (also close to T. suecica in Tigriopus). The demographics (number of nauplii, egg sacs, completion of hatching) of both copepods, using combinations of salinities in the range of 22–60 ppt and D. salina and R. salina as feeds, exhibited almost the same preference for microalgae but were negatively affected by the salinity of 60 ppt. The present experiments showed that these local copepods that have extreme salinity tolerance and a wide preference for easily cultured microalgae can be used in ecological studies and for mass production as live feed in marine fish hatcheries.