More than one-third of all sharks, rays, and chimaeras are now at risk of extinction because of overfishing, according to a new study re-assessing their IUCN Red List of Threatened Species extinction risk status. Governments and regional fisheries bodies must act now to stop overfishing and prevent a global extinction crisis.
bad fish case study answers.zip
Only buy fish that is refrigerated or displayed on a thick bed of fresh ice (preferably in a case or under some type of cover). Because the color of a fish can be affected by several factors including diet, environment, treatment with a color fixative such as carbon monoxide or other packaging processes, color alone is not an indicator of freshness. The following tips can help you when making purchasing decisions:
Through more than 30 original case studies related to contemporary conservation and management issues in fisheries, this new book challenges students to develop critical-thinking and problem-solving skills that will serve them as future natural resource professionals. Intended to encourage students to go beyond the information level of many science texts, these case studies have no right answers. Many of the cases are presented in a dilemma format, where students are asked to assess information from a variety of sources, find additional information as needed, and propose and evaluate alternative solutions. Cases are approached from a variety of dimensions (biological, ecological, political, cultural, and socioeconomic) and stakeholder perspectives. Spiral binding allows the book to lie flat for easy reference during classroom discussions and activities.
This gear is used across the world, but there are some general patterns to where certain methods are more widely used. Pole-and-line, longline, and gillnet methods are more common in lower-income countries where much of the fishing activity is subsistence or small-scale. Purse seine and trawling methods are more common in industrial fishing practices; these tend to catch more fish per unit of effort. But the downside is that they tend to have larger negative impacts, with more bycatch (catch of fish that are not the target species) and in some cases, damage to the seabed.
In the charts here we see the average per capita consumption of fish and seafood across the world.6 The highest seafood consumers are countries including Iceland, the Maldives and Hong Kong which consume over 70 kilograms per person, and in some cases upwards of 90 kilograms. Contrast that with those at the bottom of the table: Indians and South Africans consume less than 10 kilograms. Those from Ethiopia and Pakistan eat only a few.
In a new study published in Nature, Jessica Gephart and colleagues conducted a meta-analysis of the impacts of fish and seafood across multiple environmental metrics.19 To do this they combined life-cycle analysis data from studies of wild-caught and farmed seafood products. It covered over 1690 fish farms, and 1000 records from fisheries.
What has changed is where bottom trawling is happening. Trawling rates were very high across Europe in the 1950s, 60 and 70s. However, growing concern about the depletion of wild fish stocks has led to a significant reduction in recent decades, to allow populations to recover. The case of the UK, Portugal and Spain are shown in the chart. Portuguese catch from bottom trawling has fallen by 90% since the 1960s.32 In 2016, the European Commission also banned bottom trawling in deeper water, below 800 meters. We see the same in Japan, where catch peaked in 1972 at 4 million tonnes, and has since fallen by around 90% to 400,000 tonnes.
The Antarctic icefishes (Family Channichthyidae) provide excellent examples of unique traits that can arise in a chronically cold and isolated environment. Their loss of hemoglobin (Hb) expression, and in some cases, loss of myoglobin (Mb) expression, has taught us much about the function of these proteins. Although absences of the proteins are fixed traits in icefishes, the losses do not appear to be of adaptive value. Contrary to some suggestions,loss of Hb has led to higher energetic costs for circulating blood, and losses of Mb have reduced cardiac performance. Moreover, losses of Hb and Mb have resulted in extensive modifications to the cardiovascular system to ensure adequate oxygen delivery to working muscles. Recent studies suggest that losses of Hb and Mb, and their associated nitric oxide (NO)-oxygenase activities, may have accelerated the development and evolution of these cardiovascular modifications. The high levels of NO that should occur in the absence of Hb and Mb have been shown in other animal groups to lead to an increase in tissue vascularization, an increase in the lumenal diameter of blood vessels, and an increase in mitochondrial densities. These characteristics are all hallmark traits of Antarctic icefishes. Homeostatic feedback mechanisms thus may have accelerated evolution of the pronounced cardiovascular traits of Antarctic icefishes.
All three isoforms of NOS are present in fish. Endothelial NOS (eNOS) has been reported in vascular endothelium and heart muscle of developing zebrafish(Fritsche et al., 2000), and the presence of nNOS and iNOS clearly has been established in a variety of tissues from several fish species (e.g. Holmqvist et al., 1998; Holmqvist et al., 2004; Morlá et al., 2003, Pellegrino et al., 2002; Pellegrino et al., 2004). A recent study shows that nNOS is expressed at a higher level in skeletal muscle from icefishes than in the tissue from red-blooded species(Morlá et al., 2003). Both eNOS and iNOS have been identified in ventricular cardiomyocytes of white and red-blooded nototheniods, and eNOS is also found in the endothelium and epicardium in heart ventricles from these fishes(Tota et al., 2005). NO has been shown to regulate cardiovascular activities in icefish, including dilation of branchial vasculature, cardiac stroke volume and power output(Pellegrino et al., 2003). Interestingly, NO has a positive inotropic effect on cardiovascular function in icefish, whereas in other fish and mammals, NO has a negative inotropic effect (Tota et al., 2005). At this point it is unknown if this difference is related to the absence of hemoglobin, or some other species-specific difference in the expression of signaling molecules operating downstream of NO. Regardless, it seems likely that if NO is present at sufficient levels to control these processes, then it likely also contributes to the regulation of additional features of the cardiovascular and muscular system.
The extraordinary biology of channichthyid icefish was first recognized more than 50 years ago. Today we continue to learn much about basic biological processes by studying these unusual animals. The icefishes have provided a tremendous opportunity to learn more about the function of the oxygen-binding proteins hemoglobin and myoglobin, and the unique physiologies that arise in the absence of these proteins. Indeed, icefishes were around several million years before the development of the much-studied myoglobinless mice.
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