Sea urchin population harvest in the North Atlantic coast of Portugal was characterized in terms of gonad yield, nutritional composition and important market-related traits, over one reproductive cycle (March 2016 to March 2017). Most of the quality attributes showed a seasonal variation strongly dependent on sea urchin sex. Maximum gonad yield (18%) was observed in March 2017. A single spawning event occurred between May and July. Gonads are rich sources of protein (12–18% WW) with low fat content (≤6% WW), that increase during the gametogenic stages of recovery and growing (November-December). Polyunsaturated fatty acids were the dominant class in both sexes (4.2–14.7 mg.g⁻¹ WW), being preferentially accumulated in females. Total gonads carotenoid varied seasonally, with the highest level being observed in males during spawning season. Echinenone was the main pigment present in gonads, showing highest concentrations in males during spawning and gonad recovering. During the growing and early maturation period gonads were more reddish, yellowish and brighter, as well as more firm, irrespectively of the sex. Based on all seasonal changes affecting gonad yield and quality, the period between November and February seems the most suitable to harvest high quality gonads in the Atlantic coast of Portugal.

This work aimed to evaluate the digestibility of defattedHermetia illucens larvae meal (HM), and its effects as fishmeal (FM) replacement on growth performance, feed and nutrient utilisation, and whole-body composition of gilthead seabream (Sparus aurata) juveniles. To assess apparent digestibility coefficients (ADC) of defatted HM, a reference-diet (43% crude protein (CP); 17% crude lipid (CL)) and a test-diet, in which 30% of the reference diet was replaced with defatted HM, were formulated. To assess the effect of dietary FM replacement, four isonitrogenous (43% CP) and isolipid (18% CL) diets were formulated to include defatted HM at 0 (HM0), 15 (HM15), 30 (HM30), and 45% (HM45), replacing FM at 0, 22, 60, and 100%, respectively. Triplicate groups of fish (initial body weight of 32 g) were randomly assigned to the experimental diets and the growth trial lasted for 67 days. The digestibility trials were conducted in a digestibility system, and each diet was tested in triplicate. Protein, lipid, and energy digestibility of defatted HM were high (>74%). Replacement of FM by defatted HM did not compromise the ADC of protein and lipid, while ADC of dry matter and energy increased. Complete dietary replacement of FM by defatted HM had no negative effects on growth performance, feed efficiency, whole-body composition, and protein utilisation of gilthead seabream juveniles, establishing the potential of defatted HM as an alternative ingredient for aquafeeds.