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Seafood by-products from various organisms like fish, shellfish, squids, and bivalves are often thrown away as waste, even though they could be utilized in creating new types of valuable foods. Up to 75% of the entire organism consists of industrial processing wastes, which can lead to a loss of profit and ecological sustainability if natural resources are not recycled efficiently. Various types of fish parts and byproducts, such as heads, viscera, skin, bones, scales, exoskeletons, pens, ink, and clam shells, can be categorized as valuable waste based on their weight percentages, which vary depending on the species and taxonomy. This review paper delves into the extraction and valorization strategies of seafood by-products, with a focus on transforming waste into valuable resources. Marine by-products can provide bioactive substances such as collagen, peptides, polyunsaturated fatty acids, antioxidants, chitin, and catalysts for biodiesel production. This review highlights the utilization of innovative techniques like microwave- and ultrasound-assisted extraction as well as supercritical fluid extraction and subcritical water extraction to extract bioactive compounds from seafood waste efficiently. This section also discusses the optimization of extraction processes to enhance efficiency and yield. Furthermore, the paper explores the potential applications of seafood by-products across various industries, emphasizing sustainable resource utilization and the creation of high-value products to be applied in our current circular economy.

Nutritional value of black soldier fly (Hermetia illucens) larvae (BSFL) processed by three different methods of treatment was compared. The resulting products were the spray-dried BSFL (SPR), oven-dried BSFL 1 (OVN1) and oven-dried BSFL 2 (OVN2). Proximate chemical composition, and profiles of amino acids, fatty acids, minerals, heavy metals, vitamins and nucleotides were analysed and compared. The tested BSFL meals were considered to have a good profile of essential amino acids (EAAs), with leucine, lysine, valine, and histidine being the dominant EAAs. Their content of saturated fatty acids exceeded that of the unsaturated fatty acids. Vitamins B1, B2, and C were also present in the samples. Minerals such as calcium, potassium, phosphorus, sodium, magnesium, zinc, iron, manganese and copper were found to be in adequate amounts in almost all the samples. Heavy metals in the BSFL meals were mostly below 1g kg-1. Nucleotides such as inosine monophosphate and uridine monophosphate occurred in all the BSFL meals. Other nucleotides, including guanosine monophosphate, adenosine monophosphate, xanthosine monophosphate, and cytidine monophosphate were detected in either or both of SPR and OVN2. In general, the nutritional value of the BSFL meals tested in the present study was influenced by the method of processing.

The present study aimed to evaluate the feeding performance of juvenile marble goby (Oxyeleotris marmorata) on acidified diets. Five fish meal-based diets at various pH levels (2.5, 3.2, 4.3, 5.3, and 6.0 (control)) were prepared, and each of them was fed to 10 wild-caught O. marmorata juveniles (body length 7.7–9.3 cm; each fish was placed in an aquarium, hence each dietary treatment was in 10 replicates) for 20 days. Throughout the feeding trial, O. marmorata juveniles showed clear increments in the daily ingestion ratio (IR) values of AD 2.5, AD 3.2, and AD 4.3. The control diet and AD 5.3 were almost totally rejected by the fish. On day 20, the IR of AD 2.5 (0.46) and AD 3.2 (0.36) were significantly higher (P < 0.05) than those of AD 5.3 (0.1) and the control diet (0.02). In addition, 70% of fish fed AD 2.5 achieved a high IR value (0.6 – 1.0), and this was the best result among all the treatments (AD 3.2, 60%; AD 4.3 50%; AD 5.3 and control, 10%). These results suggested that acidified diets can be used to wean O. marmorata juveniles, and the recommended pH level was 2.5.

The main objective of the present study was to investigate the possibility of anchovy by-product meal (ABPM) as a protein source in the diet of red hybrid tilapia (Oreochromis spp.). Five formulated feeds were produced to contain different percentages of ABPM and soybean meal (SBM): Diet contained 100% SBM with the addition of 1% methionine; Diet contained 25% SBM and 75% ABP25 (ABP25). Diet 3 contained 50% SBM and 50% ABP (ABP50); Diet 4 contained 25% SBM and 75% ABP (ABP75), and Diet 5 contained 100% ABP (ABP100). A commercial tilapia feed was used as a control diet (CF). Fish were fed close to apparent satiation, twice a day to triplicate groups of the tilapia fingerlings (1.07 ± 0.28 g) for 10 weeks. Specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) improved with the increase of ABP inclusion in the diets. Among the ABP-based diets, the highest growth performance and feed utilization were obtained by fish fed with ABP100 (SGR: 3.1%/day; FCR: 1.9) while the least was ABP0 (SGR: 1.5%/day; FCR: 2.6). Hepatosomatic index (HSI) and viscerasomatic index (VSI) of ABP meal-based diets were slightly higher compared to ABP0 and CF (0.5 to 1.5 & 7 to 12.8 respectively). There was no significant difference in fish survival rate and condition factor among all treatment groups. Protein apparent digestibility coefficient (ADC) showed an increasing pattern with increasing ABP meal in the diet and no significant difference in crude lipid ADC among all treatments. Whole-body moisture and crude lipid were not affected by the inclusion of ABPM in the diet, while crude protein and ash parallelly increased with the increase in the inclusion level of ABPM in the diet. Findings from this study indicated that ABPM is a good protein source and could replace SBM as the dietary protein ingredient for better growth performance and feed utilization. [ABSTRACT FROM AUTHOR]

The relative eye size, types of visual cell and mosaic, and the existence of retinal tapetum in the eyes of the spotted barb Puntius binotatus were determined to gain baseline information on its visual capability. The P. binotatus acquired relatively larger eye size than the other similar sized freshwater fish species with its retina being contained both cone and rod visual cells (cone ellipsoid to outer nuclei ratio = 1: 5.7). Three types of cone were identified (double-, central single- and corner single- cones), arranging in the square mosaic, and the retinal tapetum was determined to be existed. These results evidenced that the P. binotatus has good visual capability as it possessed both the photopic and scotopic visions. Vision can be the primary sense for the P. binotatus. Further study is needed to gain more information on the vision of this species.

The jewel cichlid Hemichromis bimaculatus is a popular freshwater ornamental fish with high market demand. However, it is aggressive and difficult to be maintained in captivity. Background colours are known to influence fish aggression, but there is still no such information available on H. bimaculatus. This study was conducted to examine the influence of 6 background colours (black, white, blue, yellow, green or red) on the aggression (chasing frequency), survival, weight gain and feed intake of the H. bimaculatus, through a 60‐day culture trial. At the end of this trial, since the total feed intake and fish weight gain (except black) were similar among all treatments, the green was the most recommended background colour for the H. bimaculatus culture as it has the highest fish survival, followed by the white and yellow. Low fish survival was found under the black, red and blue; hence, these background colours were not recommended. In this study, we suspected that different background colours may induce different aggressiveness degree in the H. bimaculatus, and biting may have occurred to cause low fish survival. Also, the blue was speculated to be a stressful background colour to the H. bimaculatus. Nevertheless, further study is necessary to elucidate these hypotheses. [ABSTRACT FROM AUTHOR]