Fish meal (FM) is an industrial product, mainly obtained from whole wild-caught fish, that is used as a high protein feedstuff component in aquaculture and intensive animal farming. Contamination of FM by microplastics (MPs), the synthetic polymer particles known to be nearly ubiquitous in the marine environment, is a likely consequence of their ingestion by zooplankton and other small marine animals that through the food chain end up in the fish commercialized not only for direct human consumption but also for the industrial production of FM. Unfortunately, analytical tools for quantifying contamination of FM by synthetic polymers are not available. A newly developed procedure described here allows quantification of the total amounts of polyolefins (including ethene and propene homo- and copolymers), polystyrene (PS), and poly(ethylene terephthalate) (PET), respectively, in FM. The multi-step procedure involves a sequence of solvent extractions, hydrolytic treatments to remove the biogenic matrix mainly consisting of proteins and some lipids, and selective depolymerization for PET. The gravimetric and SEC-UV techniques employed for the quantification of polyolefins and PS, respectively, only allowed to estimate their concentration in FM at around or below 100 mg/kg each, a more accurate quantification being prevented by the interference from the organic matrix and, in the case of polyolefins, by the limited sensitivity of the quantification by gravimetry. On the other hand, the contamination by PET MPs could accurately be quantified at 12.9 mg/kg based on the dry FM mass. Ways to overcome the sensitivity limitations for PS and polyolefins by using e.g. pyrolysis-GC/MS are highlighted.

The main aim of this study was to investigate the feasibility of using soybean meal added with papain to replace half of the fishmeal used in the moist pellets (49% fishmeal and 45% trash fish) developed by the Hong Kong Agriculture, Fisheries and Conservation Department (AFCD) for culturing marine fish. Gold-lined seabream (Rhabdosargus sarba), brown spotted grouper (Epinephelus bleekeri) and pompano (Trachinotus blochii) were farmed at one of the research stations (Kat-O) of AFCD, for a period of 340 days. Results indicated that diets containing papain resulted in better fish growth (reflected by relative weight gain and feed conversion ratio) than diets without papain. In general, wet weight gain of fish depends on the amount of papain added in diet rather than the diet composition. Soybean used in conjunction with papain also contributed to a more effective growth than fish fed with the moist pellets alone. A laboratory experiment (using tanks) was conducted to study the effects of the diets on concentrations of ammonia, nitrite and nitrate in the tank water. Results showed that concentrations of ammonia and nitrate were significantly lower (p < 0.05) when the fish were fed with papain-supplemented (with or without soybean meal) diets. It is envisaged that by using plant protein incorporated with enzymes could promote better growth of marine fish and lower the adverse impact of trash fish and fishmeal on water quality of the mariculture zones.

Pangasius production in Vietnam is widely known as a success story in aquaculture, the fastest growing global food system because of its tremendous expansion by volume, value and the number of international markets to which Pangasius has been exported in recent years. While certification schemes are becoming significant features of international fish trade and marketing, an increasing number of Pangasius producers have followed at least one of the certification schemes recognised by international markets to incorporate environmental and social sustainability practices in aquaculture, typically the Pangasius Aquaculture Dialogue (PAD) scheme certified by the Aquaculture Stewardship Council (ASC). An assessment of the environmental benefit of applying certification schemes on Pangasius production, however, is still needed. This article compared the environmental impact of ASC-certified versus non-ASC certified intensive Pangasius aquaculture, using a statistically supported LCA. We focused on both resource-related (water, land and total resources) and emissions-related (global warming, acidification, freshwater and marine eutrophication) categories. The ASC certification scheme was shown to be a good approach for determining adequate environmental sustainability, especially concerning emissions-related categories, in Pangasius production. However, the non-ASC certified farms, due to the large spread, the impact (e.g., water resources and freshwater eutrophication) was possibly lower for a certain farm. However, this result was not generally prominent. Further improvements in intensive Pangasius production to inspire certification schemes are proposed, e.g., making the implementation of certification schemes more affordable, well-oriented and facilitated; reducing consumed feed amounts and of the incorporated share in fishmeal, especially domestic fishmeal, etc. However, their implementation should be vetted with key stakeholders to assess their feasibility.

Dioxins and dioxin-like polychlorinated biphenyls (dl-PCBs) in fish fillet counteract the health benefits of fish products. In this study, food waste was used as a protein alternative to replacing fishmeal commonly used in the commercial fish feed, aiming to cultivate Sabah grouper with acceptable levels of dioxins and dl-PCBs. The concentrations of dioxins and dl-PCBs, as well as the fish growth performance, were compared between the fish groups fed with food waste-based feed (FWBF) and commercial feed (Nanyu®, control). The results showed that the concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) (1.22 pg/g dry weight (d.w.)) and non-ortho-dl-PCBs (13.0 pg/g d.w.) were significantly lower (p < 0.05) in the FWBF than in the control feed (commercial feed) (PCDDs: 2.35 pg/g d.w.; non-ortho-dl-PCBs: 27.2 pg/g d.w.). The growth performance of the fish group fed with the FWBF was comparable to that fed with the control feed. There were no significant differences between the WHO₂₀₀₅-TEQ values of different fish fillets (1.00, 1.11, and 1.10 pg WHO₂₀₀₅-TEQ/g d.w. for FWBF group, control feed group, and local market fish, respectively). Based on the guidelines provided by European Food Safety Authority (ESFA) and U.S. Environmental Protection Agency (USEPA), the fish fed with the FWBF were safe for human consumption (hazard index values: 0.284–0.522; cancer risk range: 2.59–2.97 × 10⁻⁵). The findings of this study suggest that food waste could serve as an alternative protein source for cultivating Sabah grouper with acceptable levels of dioxins and dl-PCBs.

Polybrominated diphenyl ethers (PBDEs) and their hydroxylated (OH) and methoxylated (MeO) structural analogues have been found widely distributed in aquatic ecosystems, and may exhibit potential adverse effects to humans due to their bioaccumulative behavior through food chain. Fishmeal is an important animal feed applied around the world and is generally of marine origin. However, the levels and sources of PBDEs in fishmeal have not been thoroughly evaluated and their structural analogues have not been reported to date. The present study collected ninety-two fishmeal samples from world main fishmeal producing area to determine 27 PBDEs, 10 MeO-PBDEs and 11 OH-PBDEs. The concentrations of Σ₂₇PBDEs, Σ₁₀MeO-PBDEs and Σ₁₁OH-PBDEs were in the ranges of 0.1–1498 (mean: 75.8), 1.14–881 (37.4) and 1.00–47.5 (8.17) ng/g lipid, respectively. PBDEs were found primarily correlated with the historically commercial production, meaning higher production of certain commercial product in a country, higher corresponding PBDE congeners in local fishmeal. A market shift from penta- and octa-formulations toward deca-formulation was observed. BDE209 was identified as a major congener in fishmeal. Both the MeO-PBDEs and the OH-PBDEs were influenced by fishmeal producing areas (p < 0.001). High MeO-PBDEs were identified in the Southeast Asian fishmeal, which might be due to the suitable environmental conditions for the generation of bromoperoxidase-contained algae in local area. The ratio of two major MeO-PBDE congeners, 6-MeO-BDE47/2′-MeO-BDE68, were generally >1 in the northern hemisphere and <1 in the southern hemisphere in the present study, which was consistent with the results obtained from previous published papers. Both MeO-PBDEs and OH-PBDEs were in accordance with the specialties of naturally produced halogenated compounds.

Mariculture sediment has been recognized as a major contributor of environmental antibiotic resistance genes (ARGs), which are challenging the treatment of infections worldwide. Both antibiotics and fishmeal are used in aquaculture, and each has the potential to facilitate ARG dissemination, however their combined impact on the sediment resistome and their relative contribution remain unclear. In this study, microcosms were exposed to varying concentrations of tetracycline with or without fishmeal (0.1% wt/wt) for 14 days. Sediment genomic DNA was analyzed using high throughput quantitative PCR and 16S rRNA gene amplicon sequencing to compare the contribution of fishmeal and tetracycline to antibiotic resistomes and bacterial communities in mariculture sediment. Sixty-seven ARGs were detected potentially correlating to resistance for several major antibiotics. Fishmeal, but not the dose of tetracycline, contributed to the significant increase of both ARG abundance and diversity in the sediment. Based on principle coordinate analysis and hierarchical clustering, ARGs were clustered into two groups depending on whether fishmeal was added. Aminoglycoside, macrolide–lincosamide–streptogramin b (MLSb) and tetracycline resistance genes were the most abundant when fishmeal was used, while a significant increase in mobile genetic element (MGE) abundance was also detected (P < 0.05). Meanwhile, bacterial community structures were detected with distinct patterns between the two groups (Adonis, P < 0.05). Using the Mantel test and partial least squares path modeling, we identified that sediment resistomes were significantly correlated with microbial community structures (P < 0.05) which were mainly driven by nutrients in fishmeal. Together our findings suggested that fishmeal plays a more important role than tetracycline in proliferation of ARGs in mariculture sediment. This study may provide new insights into the mitigation of ARG propagation in mariculture operations.

So far, the adverse effects of excess Fe in shrimp have been ignored for years as it was thought that extra Fe supplementation was not needed in the practical diets. Nowadays, Fe concentration in commercial shrimp feed from feed enterprises could be around 301.34–545.5 mg/kg, which is mainly due to the fish meal containing up to 1500 mg/kg Fe. Therefore, the purpose of this experiment was to investigate the effects of Fe supplementation on the growth performance, tissue Fe deposition, hepatopancreas lipid metabolism, intestinal function in L. vannamei. The results showed that although growth performance was not influenced by the dietary Fe supplementation, excess Fe supplementation (955.00 mg/kg) significantly increased hepatopancreas Fe deposition and induced lipolysis. Moreover, excess Fe supplementation impaired intestinal immune function and disrupted microbiota homeostasis. These findings might provide partial theoretical evidence for the effect of dietary Fe supplementation on physiological metabolism in L. vannamei.

Presence of microplastics (MPs) in a broad range of wild and cultured marine organisms is well-documented, but transfer mechanisms by which cultured organisms are contaminated with MPs is poorly understood. MP loads in three Malaysian commercial brands of fish meal were investigated. Chemical composition of extracted MP-like particles was confirmed using micro-Raman spectroscopy. Inorganic composition of MPs and pigment particles were assessed through energy-dispersive X-ray spectroscopy (EDX). Out of 336 extracted particles, 64.3% were plastic polymers, 25% pigment particles, 4.2% non-plastic items, and 6.5% were unidentified. Fragments were the dominant form of MPs (78.2%) followed by filaments (13.4%) and films (8.4%). This study demonstrates that cultured organisms could be exposed to high levels of MPs via MP contaminated fish/shellfish used in fish meal production. Fish meal replacement with other sources of protein including meat meals and plant-based meals may mitigate MP exposure to cultured or farmed organisms.

In this study, heavy metal levels in sediments, human hair, and fish muscle tissue as well as organic matter (OM%) content in surface sediments of Chabahar Bay were determined to assess their ecological risks and sources. Totally, 96 samples were collected from 16 stations (Tiss, Konarak, desalination plant, entrance of Chabahar Bay, Posm, Ramin, and reference stations) and were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). Abundances of elements were of the following order: Ca>Al>Fe>Mg>Na>K>S>P>Ti>Mn>Sr>Ba>Cr>Ni>V>Li>Zn>Cu>Co>Pb>As>Cd>Ag>Se>Sb>Be>Mo>Bi. Element levels in sediments were within the range of low pollution areas, except for Cr, As, Ni, and Cd. Dominant sources of elements were natural, except for Cd, which was anthropogenic. All geo-accumulation index (Igₑₒ) values were less than zero, except for Ag, Cd, and Sr from heavily to moderately contaminated areas. Eᵣⁱ values indicated low ecological risk, except for Cd which showed a high ecological risk. The As levels limit the consumption of fish meal per month.

Microalgae have been used as live food in aquatic species. In recent years, the interest in microalgae has considerably increased, thanks to the evolution of production techniques that have identified them as an ecologically attractive aquafeed ingredient. The present study provides the first data about the effects of dietary inclusion of a microalgae consortium grown in a high-rate algal pond system on zootechnical performance, morphometric indices, and dietary nutrient digestibility as well as morphology and functionality of the digestive system of European sea bass, Dicentrarchus labrax. A dietary treatment including a commercial mono-cultured microalgae (Nannochloropsis sp.) biomass was used for comparison. Six hundred and thirty-six European sea bass juveniles (18 ± 0.28 g) were randomly allotted into 12 experimental groups and fed 4 different diets for 10 weeks: a control diet based on fish meal, fish oil, and plant protein sources; a diet including 10% of Nannochloropsis spp. biomass (100 g/kg diet); and two diets including two levels (10% and 20%) of the microalgal consortium (100 and 200 g/kg diet). Even at the highest dietary inclusion level, the microalgal consortium (200 g/kg diet) did not affect feed palatability and fish growth performance. A significant decrease in the apparent digestibility of dry matter, protein, and energy was observed in diets including 10 and 20% of the microalgal consortium, but all fish exhibited a well-preserved intestinal histomorphology. Moreover, dietary inclusion with the microalgal consortium significantly increased the enzymatic activity of maltase, sucrase-isomaltase, and ɤ-glutamil transpeptidase in the distal intestine of the treated European sea bass. Algal consortium grown using fish farm effluents represents an attempt to enhance the utilization of natural biomasses in aquafeeds when used at 10 % as substitute of vegetable ingredients in diet for European sea bass.