Ionic aspects of the physiology and biology of Macrobrachium rosenbergii (De Man) 1879.

The giant Malaysian freshwater prawn, Macrobrachium rosenbergii spends its juvenile and adult life primarily in freshwater. The larval stages of this species require brackishwater for their survival and development. Adult females of Macrobrachium rosenbergii migrate into brackishwater to spawn, and some populations of this prawn live entirely in brackishwater. Other Macrobrachium species have larval stages that require brackishwater for development. Some Macrobrachium species do not require brackishwater for larval survival and have abbreviated larval development. The ,ionic requirements for successful larval development and metamorphosis were studied using a formulated artificial seawater. It was found that trace element impurities, either in the salts used in the artificial seawater, or contained within the artemia fed to the larvae, were sufficient to allow normal larval development. The omission of bromide from the artificial seawater was found to cause total mortality to early stage larvae. Further work attempted to discover the minimum threshold concentration of bromide required by the larvae. The manner by which Macrobrachium rosenbergii adults regulate the ionic composition of their haemolymph when exposed to freshwater and brackishwater of varying salinity was investigated. The effect of the moult cycle on divalent cation regulation is studied. It was found that in varying salinity adult Macrobrachium showed a strong regulation of its haemolymph osmotic pressure, Na, Cl, Mg, Ca, K and Sr concentrations. The haemolymph Ca and Br concentration increased with increasing salinity, while the haernolymph Cu concentration decreased. The high concentration of bromide and strontium in the haemolymph of prawns held in freshwater was regarded as an indication that they might be essential to the adult prawn. The implication of their roles was in the process of cuticle hardening. A close relationship between haemolymph strontium and magnesium concentrations was revealed, although the significance of this is uncertain. The effect of the moult cycle on haemolymph divalent cation regulation revealed that Ca and Cu decreased after the ecdysis. Haemolymph magnesium concentrations were elevated during pre- and postmoult. Strontium increased markedly prior to ecdysis, this was further evidence as to a potential role in the calcification process. The haemolymph bromide concentration was reduced during pre- and postmoult. This was attributed to, either its incorporation into the cuticle, or increased ionic fluxes during the pre- and postmoult period. The calcification of the larval stages of Macrobrachium rosenbergii was investigated. The larvae are calcified in a similar manner to the postlarvae. Concentrations of strontium and bromine in the postlarvae decrease when they are transferred to freshwater. Analysis of larval exuviae revealed high concentrations of bromine (=1000ppm) confirming its role in the sclerotisation of the larval cuticle. A close relationship was found between the strontium and magnesium concentrations of the larvae and postlarvae held in seawater, confirming this discovery in the adult haemolymph. Such a relationshipwas not found between these ions and calcium. Salinity did not affect the function of Macrobrachium rosenbergii haemocyanin significantly. This was attributed to the relatively stable internal ionic environment that this prawn is able to maintain over a wide range of salinities. Temperature had a pronounced effect on the haemocyanin oxygen affinity. The oxygen transporting characteristics of Macrobrachium rosenbergii haemocyanin were similar to those found for marine and brackishwater crustaceans. The P02 of Macrobrachium rosenbergii haemolymph was found to be substantially lower than the P02's recorded for marine and bracklshwatar species. This was attributed to a reduced perfusion of the gills by haemolymph. The reason for this was supposed to be a means by which this prawn reduces its permeability, and hence loss of ions, when in freshwater

Victimization of the Homeless: Public Perceptions, Public Policies, and Implications for Social Work Practice

Homeless individuals are particularly vulnerable to victimization, sometimes resulting in fatalities. Theories of victimization prove useful to understanding the risks inherent in being homeless as well as the public’s perception of the homeless population. Problematically, public policy that criminalizes this population may exacerbate the victimization of this group. Municipalities have turned to law enforcement and the criminal justice system to respond to people living in public spaces. Programs that ensure adequate income, affordable housing, and supportive services to prevent homelessness and address the needs of those who are homeless are essential. In addition, increased law enforcement training and the implementation of legislation to include homeless persons as a protected class in hate crime statutes is needed. In effect, these interventions focus on reducing the risks associated with being homelessness—in turn reducing the risk of their further victimization. Social workers are both uniquely positioned and ethically obligated to support these efforts and contribute to the social inclusion of people who are homeless or at risk of becoming homeless

Intersectorality in the governance of inland fisheries

© 2018 by the author(s). One of the defining characteristics of inland fisheries is that they are closely impacted by other essential human activities that rely on the same fresh or brackish water ecosystems, such as hydroelectricity generation and irrigated agriculture. Starting with the premise that an understanding of fisheries' interactions with these external sectors is in itself critical for achieving sustainability of the fisheries, this paper explores the topic of intersectoral governance and outlines an approach to analyzing the intricate and often challenging sector relationships. By drawing on examples of inland fisheries from around the world, the paper proposes four broad discursive mechanisms that can structure the study of the intersectoral dynamics, i.e., system characterization, valuation, power relations, and vertical policy interaction. A synthesis model then demonstrates their interwoven nature, revealing the way each mechanism influences one another as together they shape overall outcomes. It is apparent that analyses often need to be combined to advance more rigorous (and transdisciplinary) science and also inform appropriate courses for the governance of inland fisheries. Given the typically marginal position of fisheries in inland water-use discussions, we call for a more systematic understanding of intersectoral interactions to enhance the sector's resilience within the wider society and subsequently contribute to integrated governance of waterbodies

Choosing best practices for managing impacts of trawl fishing on seabed habitats and biota

Bottom trawling accounts for almost one quarter of global fish landings but may also have significant and unwanted impacts on seabed habitats and biota. Management measures and voluntary industry actions can reduce these impacts, helping to meet sustainability objectives for fisheries, conservation and environmental management. These include changes in gear design and operation of trawls, spatial controls, impact quotas and effort controls. We review nine different measures and actions and use published studies anda simple conceptual model to evaluate and compare their performance. The risks and benefits of these management measures depend on the extent to which the fishery is already achieving management objectives for target stocks and the characteristics of the management system that is already in place. We offer guidance on identifying best practices for trawl-fisheries management and show that best practices and their likelihood of reducing trawling impacts depend on local, national and regional management objectives and priorities, societal values and resources for implementation. There is no universalbest practice, and multiple management measures and industry actions are required to meet sustainability objectives and improve trade-offs between food production and environmental protection

Maintaining Diversity of Integrated Rice and Fish Production Confers Adaptability of Food Systems to Global Change

Rice and fish are preferred foods, critical for healthy and nutritious diets, and provide the foundations of local and national economies across Asia. Although transformations, or "revolutions," in agriculture and aquaculture over the past half-century have primarily relied upon intensified monoculture to increase rice and fish production, agroecological approaches that support biodiversity and utilize natural processes are particularly relevant for achieving a transformation toward food systems with more inclusive, nutrition-sensitive, and ecologically sound outcomes. Rice and fish production are frequently integrated within the same physical, temporal, and social spaces, with substantial variation amongst the types of production practice and their extent. In Cambodia, rice field fisheries that strongly rely upon natural processes persist in up to 80% of rice farmland, whereas more input and infrastructure dependent rice-shrimp culture is expanding within the rice farmland of Vietnam. We demonstrate how a diverse suite of integrated production practices contribute to sustainable and nutrition-sensitive food systems policy, research, and practice. We first develop a typology of integrated production practices illustrating the nature and degree of: (a) fish stocking, (b) water management, (c) use of synthetic inputs, and (d) institutions that control access to fish. Second, we summarize recent research and innovations that have improved the performance of each type of practice. Third, we synthesize data on the prevalence, outcomes, and trajectories of these practices in four South and Southeast Asian countries that rely heavily on fish and rice for food and nutrition security. Focusing on changes since the food systems transformation brought about by the Green Revolution, we illustrate how integrated production practices continue to serve a variety of objectives to varying degrees: food and nutrition security, rural livelihood diversification and income improvement, and biodiversity conservation. Five shifts to support contemporary food system transformations [i.e., disaggregating (1) production practices and (2) objectives, (3) utilizing diverse metrics, (4) valuing emergent, place-based innovation, (5) building adaptive capacity] would accelerate progress toward Sustainable Development Goal 2, specifically through ensuring ecosystem maintenance, sustainable food production, and resilient agricultural practices with the capacity to adapt to global change.This work was undertaken as part of the CGIAR Research Program on Fish Agri-Food Systems (FISH) led by WorldFish with contribution from the CGIAR Research program on Water Land and Ecosystems (WLE) led by the International Water Management Institute. Both these programs are supported by contributors to the CGIAR Trust Fund. Additional funding support for this work was provided by the Australian Government and the Australian Centre for International Agricultural Research grant work was provided by the Australian Centre for International Research through the Development of Rice Fish Systems in the Ayeyarwady Delta, Myanmar (ACIAR project FIS/2016/135). The support through the United States Agency for International Development under Cooperative Agreement No. AID-OAA-L-14-00006 and KAES contribution number 20-317-J and grant number AID-442-IO12-00001 are duly acknowledged. Photo credits: Anon., Finn Thilsted, Anon., Anon., Todd Brown (Figure 1)

Collateral damage? Small-scale fisheries in the global fight against IUU fishing

© 2020 The Authors. Fish and Fisheries published by John Wiley & Sons Ltd Concern over illegal, unreported and unregulated (IUU) fishing has led to a number of policy, trade and surveillance measures. While much attention has been given to the impact of IUU regulation on industrial fleets, recognition of the distinct impacts on small-scale fisheries is conspicuously lacking from the policy and research debate. In this paper, we outline three ways in which the application of IUU discourse and regulation undermines small-scale fisheries. First, the mainstream construction of “illegal,” “unreported” and “unregulated” fishing, and also the categorical use of “IUU” in an all-inclusive sense, disregards the diversity, legitimacy and sustainability of small-scale fisheries practices and their governing systems. Second, we explore how the recent trade-related measures to counter IUU fishing mask and reinforce existing inequalities between different sectors and countries, creating an unfair burden on small-scale fisheries and countries who depend on them. Third, as IUU fishing is increasingly approached as “organized crime,” there is a risk of inappropriately targeting small-scale fisheries, at times violently. Reflecting on these three trends, we propose three strategies by which a more sensitive and ultimately more equitable incorporation of small-scale fisheries can be supported in the global fight against IUU fishing

Stocking fish in inland waters: Opportunities and risks for sustainable food systems

Stocking is one of the foremost tools in the inland fisheries management toolbox, but it comes with both opportunities and risks. Stocking is often used as compensation for depleted wild populations, particularly where recruitment processes have been disrupted, but it can introduce disease, disrupt community structures, reduce genetic integrity, and cause conflicts between fishery stakeholders. Despite its widespread use, examples of effective stocking for food fisheries in inland waters are sparse in the peer-reviewed literature. Nevertheless, it is well established that stocking is frequently used to maintain fish yield, so there is a need to conduct the practice in a robust manner that minimises the potential risks. This paper serves as the front matter for a special section of Fisheries Management and Ecology focused on fresh waters feeding the world, which resulted from two panel sessions, one focused on aquaculture and one focused on stocking, hosted by the international InFish research network (https://infish.org/). The paper highlights current practices of fish stock enhancement in inland waters for food, examines potential synergies and interactions of stock enhancement programmes with aquaculture, and provides an outline framework for responsible management of fish stock enhancement