Fisheries and Aquaculture

This volume examines fisheries and aquaculture. The chapters in this volume synthesize the current understanding of the diverse topics in fisheries and aquaculture. The first part of the book explores worldwide crustacean fisheries and concludes with two chapters on harvested crustaceans that are usually not within the focus of the mainstream fisheries research, possibly because they are caught by local fishing communities in small-scale operations and sold locally as subsistence activity. In the second part of the book, the authors explore the variety of cultured crustacean species. The chapters of the third part of the volume focus on important challenges and opportunities, including diseases and parasitism, the use of crustaceans as bioindicators, and their role in biotechnology. Collectively, these 19 chapters provide a thorough exposition of the present knowledge across the major themes in crustacean fisheries and aquaculture.

Crustaceans as Fisheries Resources: General Overview

Much of the biological and other research efforts on crustaceans have been driven by their importance to humans as a food source. Production comes from a diverse array of methods and scales of extraction, from small recreational or subsistence fisheries to industrial-scale operations. Most crustacean catch comes from shrimp fisheries, with over two million tons taken in 2014, mainly by trawl. The genera Acetes, Fenneropenaeus, and Pandalus account for around three quarters of this catch. Crab, krill, and lobster are the other main crustacean products (around 600,000 t crab, 380,000 t krill, and 300,000 t lobster in 2014). Trends in crustacean fisheries are broadly similar to those of other seafood, although crustaceans often target different market segments and receive higher prices than fish. Crustacean fisheries management faces many challenges with management of bycatch from trawl gears especially significant. Fortunately, crustaceans tend to be easily handled with low discard mortality, and this has enabled widespread use of regulations based on size, maturity, or sex (e.g., male-only fisheries). Total allowable catch (TAC) limits are widely used and highly effective for ensuring sustainable harvests when set responsibly using good information. TAC systems are often combined with catch share or individual transferable quota systems, which had a mixed history in crustaceans, sometimes reducing overall community benefit. This parallels the challenge facing fisheries globally of ensuring that harvests are not only sustainable but also deliver benefits to the wider community beyond the commercial fishers; management of some crustacean fisheries is at the forefront of these developments.

Inland Crustacean Fisheries

Freshwater crustacean inland fisheries are typically confined to small local areas that are associated with bodies of water, like rivers and swamps. They are small-scale fisheries, enough to supply the requirements for local commercial use, and considered mainly as a subsistence resource for small fishing communities. As such, inland crustacean fisheries exemplify a subsistence opportunity for small countries with limited economic power, particularly rural communities. Crustaceans are a relevant protein source alternative to fish, and they are often also associated with local gastronomical and cultural identity. Data for the most commonly caught species are often unavailable since these fisheries exist in remote areas where government or institutional monitoring is limited, making it difficult to obtain reliable data about small-scale fisheries. Nonetheless, the captured species and the techniques used are widely diverse. In inland fisheries, the main target species are prawns from the genus Macrobrachium, gathered within the tropics all over the world. Natural fisheries of crayfishes in their native range exist on several continents, with Procambarus clarkii, Pacifastacus leniusculus, and Astacus astacus as the main commercial species. Some of them have also become a fisheries resource in areas where they were introduced. The only terrestrial crab fishery is for an anomuran, the coconut crab Birgus latro. The future of most of these fisheries depends in part on the health of the water sources threatened by contamination and unrestricted waterways jeopardized by the construction of dam-like structures that block the migration of some species to complete their reproductive cycles. The creation of regulatory policies is key for keeping the fishery activity self-sustainable because most of the exploitation depends on wild populations. There are some conservation efforts implemented thanks to the relevant gastronomical value of the species, as well as to economically sustain local communities in remote areas.

Biological traits and population dynamic of Parapenaeus longirostris (Lucas, 1846) in the Marmara Sea, Turkey

Parapenaeus longirostris is a valuable resource for the crustacean fisheries in the Marmara Sea, therefore, in this study length-weight relationships, growth, mortality, reproduction, recruitment patterns, the probabilities of capture and per recruit analyses were determined. Total 36288 samples were collected by beam trawl between September 2011 and July 2014 in 229 sampling stations. The total length (TL), body weight (g) and carapace length (CL) values ranged between 34 -175 mm, 0.2 - 28.9 g and 8 - 41 mm, respectively. CL-weight relationship equations were calculated for females, males and combined sexes, respectively, W=0.0023×CL2.5, W=0.0029×CL2.43, W=0.0022×CL2.52. The growth parameters were determined as L∞=199.5 mm, k=0.47, t0=-0.5 in TL, L∞=36.8 mm, k=0.37, t0=-0.69 in CL. L25, L50, and L75 values were found to be 15.15 mm, 16.29 mm, 17.44 mm for males and 16.62 mm, 18.07 mm, 19.52 mm for females. The sexual maturity length for females was found 27.3 mm CL and the exploitation rate was found at 0.62 for the whole population.

Ocean acidification could cost the UK's shellfish industry £6 billion

Shellfish harvesting accounts for over ⅓ of total fisheries landings by value in the United Kingdom. Contributing over £400 million each year, shellfish aquaculture and the wild-capture shellfish, mollusk, and crustacean fisheries are important economic drivers in the UK. Ocean acidification could affect some of these species, affecting their survival as some of their shells could be affected by low pH conditions. To understand the monetary effects of ocean acidification, the authors calculated the costs of lost shellfish harvesting on the UK economy.