Fisheries and Aquaculture
In 2012, the combined world fishery and aquaculture production reached 158 million tons. The production has been steadily rising since the 1950s when production was ca. 20-25 million tons. In the latest top-18 ranking of producer countries (for 2012) listed by FAO (2014), several countries, such as China (with ca. 14 million tons), Indonesia (5.4 million tons), the USA (5.1 million tons), Peru (4.8 million tons), Russian Federation (4 million tons), Japan (3.6 million tons), India (3.4 million tons), Chile (2.6 million tons), Viet Nam (2.4 million tons), Myanmar (2.3 million tons), the Philippines (2.1 million tons) or Norway (2.1 million tons) exceeded the 2 million tons/year and in total they represented about 76% of world total.
The rising world catches are fairly diverse in terms of commercial and functional groups but dominated by perch-like, herring-like, cod-like fishes, tunas and billfishes and anchovies, and consisting mostly of pelagics, small and medium demersals and large benthopelagics, respectively. Worldwide, fishery catches in oceans and seas represent ca. 90% of total catches.
In decreasing order, Anchoveta (Engraulis ringens) with 4.7 million tons, Alaskan polock (Theragra chaclchogramma) with 3.3 million tons, skipjack tuna (Katsuwomus pelamis) with 2.8 million tons, Sardinellas spp. (2.3 million tons), Atlantic herring (Clupea harengus) with 1.8 million tons, chub mackerel (Scmober japonicas) with 1.6 million tons, Scads (Decapterus spp.) and yellowfin tuna (Thunnus albacares) with 1.4 million tons each, Japanese anchovy (Engaulis japonicas) with 13 million tons and largehead hairtail (Trichiurus lepturus) with 1.2 million constitute the top-10 species most fished worldwide.
On the other hand, aquaculture production already represents (in 2012) more than 40% of worldwide seafood production with China (ca. 65%) and other Asian and Pacific countries (26%) representing about 90% of total aquaculture production.
Only 15 countries, mostly from Asia (China (ca. 62%), India, Viet Nam, Indonesia, Bangladesh, Thailand, Myanmar, Philippines, Japan, Republic of Korea) but also from Europe (Norway), the Americas (Chile, Brazil, USA) and Africa (Egypt), are responsible for almost 93% of total aquculture production in the world.
Fish and Seafood Products Utilization
In 2012, more than 86% of world fish production, i.e., 136 million tons, was utilized for direct human consumption. The remaining amount (21.7 million tons) was destined to non-food uses, mostly reduction to fishmeal and fish oil (75%) but also utilized as ornamental fishes, as fingerlings/fry for culture purposes, as bait, for pharmaceutical uses and as raw material for feeds (14%). Edible seafood products are primarily consumed live, fresh or chilled (ca. 40%), then in frozen form (about 29%) and less so in cured (dried, salted, smoked or other forms; 12%) and prepared or preserved forms (13%).
Utilization and processing methods show marked continental, regional and national differences with marked differences between developed and developing countries’ markets. The former favouring frozen and other processed forms while in the later fish is commercialized mainly live or fresh soon after landing or harvesting, or processed using traditional preservation methods, such as salting, drying and smoking. Nevertheless, developing countries have experienced a growth in the share of fish production utilized as frozen products (from 13% to 24% in the 1992-2012 decade).
Social and Economical Importance
The social significance and economical value of fisheries and aquaculture are evident. According to FAO, in 2012, 58.2 million people worked in capture fisheries and aquaculture (of which 37% are full time and 23% part-time). Most (84%) of all people employed in the fisheries and aquaculture sector were in Asia, followed by Africa (>10%). Employment in the sector has grown faster than the world’s population. Overall, fisheries and aquaculture assure the livelihoods of 10–12% of the world’s population.
In 2012, about 200 countries reported exports of fish and fishery products. The fishery trade is especially important for developing nations (in some cases accounting for more than half of the total value of traded commodities). In addition, fish exports are a valuable source of foreign exchange for many developing countries, which export more than they import.
Fishery exports declined slightly but still represented 129.2 billion USD in 2012 while aquaculture production peaked at 144.4 Billion USD. Together, they are equivalent to the gross domestic product of a developed country such as Finland (ranked 40th in the world).
SEAFOOD QUALITY
Quality characteristics of fish and seafood products are comprehensively presented in a number of books only an introductory, brief account is given here.
In terms of nutritional composition, fish and fishery products have a very high water content (50-85%), are rich in protein (12-24%) but poor in carbohydrates (0.1-3%), and their lipid content is quite variable (0.1-22%). Besides, fish and fishery products constitute important sources (0,8-2%) of minerals (K>P>Na>Mg>Ca>Zn>Cu) and vitamins (B that is water soluble, and A, D and E that are fat-soluble, thus occurring in fatty fish and molluscs).
Most of the proteins, 80-90%, constitute the muscle while the remaining are non-protein, nitrogenous compounds, such as volatile bases (ammonia, methylamine, dimethylamine and trimethylamine), trimethylamine oxide (TMA-O), creatine, free amino acids (AA), nucleotides, purine bases and urea in the case of cartilaginous fish, that influence the sensory characteristics and are important in the process of fish and fishery products deterioration. On the other hand, lipid content is quite variable even in the same species, depending on reproductive cycle stage/sexual maturity, growth, water temperature, food abundance and quality, stress, etc.
All these characteristics make fish and fishery products highly prone to post-mortem deterioration due to autolithic (A), microbiological (M) and chemical (Q) phenomena. A number of signs e.g., development of unpleasant tastes and smells (due to A, M, Q), the formation of mucous and production of gas (M), the changes in color/abnormal coloration (A, (M), Q) and changes in texture (A, (M)).
Species-related factors, such as anatomy (size, skin thickness, etc.), physiology (enzymes, pH, etc.) and habitat (e.g., water quality, pollution), and the manipulation of fish and seafood, e.g., capture (fishing gear/method), production (feed, water quality, slaughter, etc.), transportation (maritime and in-land), processing (on-board or in-land), affect its quality loss and spoilage.
Seafood products are marketed and consumed in a wide spectrum of forms (chilled fresh, modified atmosphere packed, marinated, salted, canned, etc.) in order to fulfill consumers’ demands. Emerging technologies (i.e., high-hydrostatic pressure, ionizing radiation, chitosan coating, etc.) and novel packaging forms that have positive effects on the utilization of raw fishery products and contribute to the quality and safety of both raw and processed products are becoming widely used. The increased demand for fishery products in recent decades has been accompanied by growing awareness of quality and safety, and nutritional aspects as well as attention to waste reduction and valorization of by-products. Due to the nutritional composition, weak connective tissue, and high moisture content, fishery products are very perishable foods.
After harvesting or catch, seafood is prone to spoilage through microbial growth, chemical change and breakdown by endogenous enzymes and can rapidly become improper for Human consumption and possibly dangerous to health. In this context, following the good hygienic/manufacturing practices, proper handling, processing, preservation, packaging and storage measures from sea to dish (Figure 4) are essential to improve fishery products shelflife, guarantee its safety, preserve its quality and nutritional attributes and avoid waste and losses.
The methods used to assess the freshness (and/or quality) of seafood can be divided into sensory and instrumental.
The former, that included the Torry scale, the EU scheme or the Quality Index Method, are also deemed (more) subjective, while the later are considered (more) objective and include numerous (bio)chemical (e.g., K-value, TVB-N, and TBARS), physicochemical (e.g., colorimeter, Torrymeter, texture profile analysis, e-nose, and Vis-NIR spectroscopy) and microbiological methods (e.g., total viable counts, coliforms, and specific spoilage organisms). Nevertheless, the increased demand for fish products in recent decades imposed the adoption of increasingly stringent hygiene measures, at national and international trade levels, to account for food safety and consumer protection. Various parameters (not only those mentioned above) and methodologies, both traditional and more technologically demanding, are presented in the next chapters of this handbook, particularly for undervalued and/or less studied species or locales.
SEAFOOD SAFETY
Seafood is rich in terms of nutritional composition, making seafood a preferable when trying to maintain a healthy life. However, due to habitat, species or group-specific (e.g., finfish, mollusk, crustacean) biological characteristics, fishing grounds and season, there are hazards, biological and chemical, that might have serious health effects (causing illnesses, sometimes fatal) after consumption, particularly of raw (fish and shellfish) and contaminated seafood. These include virus, bacteria, parasites and biotoxins that already occur in seafood at pre-harvest. Moreover, there is no reliable and accurate preventive method to determine the risk’s level during harvesting. However, during processing and/or handling there are established, demonstrated methods to control and maintain the quality and safety and to prevent (re-)contamination of seafood products such as pre-requisite programs (good hygiene practices (GHP), good manufacturing practices (GMP)) and the HACCP system . Additionally, controlling the growth of pathogenic microorganisms in seafood, that eventually limit the shelf life of the product, is also necessary not to. The main parameter that affects the growth of spoilage and pathogenic microorganisms which contaminate and/or have re-contaminated the product is temperature. Thus, proper handling, processing and application of preservatives plays a significant role in controlling and maintaining the safety of seafood. A number of risk assessment models for biological hazards and detection methodologies for chemical hazards published in the literature. In the next sections, existing biological and chemical hazards together with their detection and prevention methods are compiled and discussed.
Biological Hazards
Public health problems can be caused by many factors such as environmental conditions, climate change, and tobacco and health equity. However, most of the reports regarding public health issues showed that the main problem is coming from the consumption of contaminated food. Seafood as a very perishable food poses a high level of risk and can harbour a wide range of biological agents (i.e., bacteria, virus, and parasites). Once unfit or contaminated seafood is consumed, symptoms can arise in 1 to 7 days. Some symptoms are very mild (i.e.abdominal cramps and low-temperature fevers). In contrast, there are some severe symptoms depending on the type of biological hazard that need to be treated in the hospital (i.e., bloody diarrhea, haemolytic uremic syndrome caused by E. coli O157:H7, liver disease by V.parahaemolyticus, enteric fever, urinary tract infections by Salmonella serovars, toxic megacolon, bacteremia, Reiter’s syndrome by Shigella species, acute, symmetric, descending flaccid paralysis by Clostridium botulinum, diarrhea, vomiting, nausea, abdominal cramps, and sometimes headaches, myalgias, and low-grade fever by norovirus.
As the vegetative cells and spores of the microorganisms are widely spread in the aquatic environment, contamination is very likely before harvesting or at the final preparation of the product (i.e., processing). Growth or survival of the pathogens is also depending on the processing methodologies (application of non-thermal technologies such as ionizing radiation, high-hydrostatic pressure, thermal technologies, packaging such as MAP, salting, freezing, marinating), storage and transportation temperatures, and hygienic procedures.
On the other hand, regardless the contamination, re-contamination of lightly preserved seafood and/or undercooked or raw products also poses health risks to the consumers. To control the contamination level, authorized agencies play a very significant role from harvesting area to the retail level (“from sea to dish”).
Chemical Hazards
Occurrence of chemical hazards in seafood is generally due to improper conditions of the catch area which are contaminated by marine toxin producers (i.e., dinoflagellates and diatoms). The toxins produced by these aquatic organisms accumulates in filter feeding shellfish, namely mussels, oysters, scallops and clams. The shellfish is not affected by the toxins, however, the higher the concentration of the toxin in the edible portion of the shellfish, the higher the risk of (chemical) poisoning after consumption. Depending on the accumulated quantity of toxin the symptoms vary. Notwithstanding, a number of health conditions arise: amnesic shellfish poisoning (ASP), paralytic shellfish poisoning (PSP), neurologic shellfish poisoning (NSP), diarrhetic shellfish poisoning (DSP), azaspiracid shellfish poisoning (AZP), spirolides and gymnodimines (cyclic imines). In the period 1992-1996, 5-28% ofreported seafood-borne disease outbreaks were by caused by biotoxins.
Another type of seafood-borne toxin that can be poisonous is scombrotoxin. Compared to biotoxins the prevalence of scombrotoxin poisoning is higher (51% of the cases in 1992-1996). Scombrotoxin (or histamine) poisoning is the result of decarboxylation of free histidine by bacteria such as Morganella morganii, Klebsiella pneumonuae, K. oxytoca, Plesiomonas shigelloides, Enterobacter intermedium, Serretia mercescens, S. plymuthica and S. fonticola in the fish species that belongs to Scombroid family.
In "Handbook of Seafood - Quality and Safety Maintenance and Applications", Ismail Yüksel Genç, Eduardo Esteves and Addulla Diler (editors), Nova Science Publishers, New York, 2016, excerpts pp. 2-9. Adapted and illustrated to be posted by Leopoldo Costa.