Fisheries, Sustainability and Development

ICES Journal of Marine Science, 2000

Global Biogeochemical Cycles, 2002

1] Localized upwelling is a strong driver of primary production in many regions of the open ocean. This is achieved through providing an increased vertical flux of nutrients to otherwise starved surface waters. The impact of such upwelling hot spots on regional production is investigated with particular emphasis on three parameters: the fraction of the region experiencing upwelling, the increase in nutrient flux within upwelling regions with respect to ambient waters, and the rate of horizontal mixing between upwelled and ambient waters. It is demonstrated that although independently increasing one of these parameters has a limited effect on the production of the region, increasing them simultaneously can dramatically increase production. Furthermore, it is shown that the spatial distribution of upwelling regions can have a strong influence on productivity. Numerous small upwelling regions increase production significantly more than one large upwelling hot spot even if the total rate of upwelling is constant for the two cases. The magnitude of this discrepancy is shown to be influenced by the presence of coherent structures such as eddies in the surface ocean. The ocean components of global carbon cycle models are still far from being able to resolve mesoscale features fully. These results imply that such models may be greatly underestimating primary production in large parts of the ocean as a consequence.

Coastal ocean …, 2008

Frontiers for Young Minds

At the eastern side of the Atlantic and Pacific Oceans, Earth’s rotation combined with winds blowing toward the equator push water away from the coasts. Deep ocean water rises to replace what was pushed away, in a process called upwelling. The colder, deep water that rises to the surface is rich in nutrients and oxygen, and it supports healthy ecosystems. That is, upwelling in coastal oceans equals lots of fish! There are four coastlines where upwelling is crucial, known as eastern boundary upwelling systems (EBUS for short). These regions cover <3% of the world’s ocean area, but they are responsible for 20% of the global fish catch. EBUS change constantly along with Earth’s changing climate. Given their extraordinary biological productivity, it is very important to understand how global warming may impact EBUS. In this article, we describe what EBUS are and discuss how climate change may affect them and the fish populations in their ecosystems.

1990

Egestion: the process by which undigested food is eliminated by an organism in the form of faeces. End-to-end model: model of marine ecosystems with representation of the dynamic effects of both the physical environment and human activities on living organisms, ranging from the lowest trophic levels (phytoplankton and zooplankton) to the highest trophic levels (fish, birds and mammals). ENSO: the El Niño Southern Oscillation is a global event arising from an oscillation in the surface pressure (atmospheric mass) between the south-eastern tropical Pacific and the Australian-Indonesian regions. When the waters of the eastern Pacific are abnormally warm (an El Niño event), sea-level pressure drops in the eastern Pacific and rises in the west. The reduction in the pressure gradient is accompanied by a weakening of the low-latitude easterly in a given year and thereby becoming available to the fisheries.at developing realistic and robust models at different levels of organisation and a...

2010

Fish and Fisheries, 2014

Understanding the mechanisms driving fisheries production is essential if we are to accurately predict changes under climate change and exploit fish stocks in a sustainable manner. Traditionally, studies have sought to distinguish between the two most prominent drivers, 'bottom-up' (resource driven) and 'top-down' (consumer driven); however, this dichotomy is increasingly proving to be artificial as the relative importance of each mechanism has been shown to vary through space and time. Nevertheless, the reason why one predominates over another within a region remains largely unknown. To address this gap in understanding, we identified the dominant driver of commercial landings within 47 ecosystems, encompassing a wide range of biogeochemical conditions and fishing practices to elucidate general patterns. We show that bottom-up and top-down effects vary consistently with past fishing pressure and oceanographic conditions; bottom-up control predominates within productive, overfished regions and top-down in relatively unproductive and under-exploited areas. We attribute these findings to differences in the species composition and oceanographic properties of regions, together with variation in fishing practices and (indicative) management effectiveness. Collectively, our analyses suggest that despite the complexity of ecological systems, it is possible to elucidate a number of generalities. Such knowledge could be used to increase the parsimony of ecosystem models and to move a step forward in predicting how the global ocean, particularly fisheries productivity, will respond to climate change.

2021

Three-fourths of the world's marine capture fisheries are at or beyond 'full exploitation', indicating the likelihood that many fish populations, and the ecosystem of which they are a part, will decline (if they are not already) with current and expanded levels of competitive extraction, though the geographies of fisheries decline and recovery are uneven. Fish, whether saltwater or freshwater, farmed or captured, are an important source of animal protein, micronutrients and fatty acids crucial to alleviating malnutrition, hundreds of millions of people are employed as fish workers and in fisheries-related activities, and fish exports from developing countries generate a higher export value than coffee, bananas, cocoa, tea, sugar and tobacco combined (Campling et al. 2012). State and market pressures from outside fishing industries also shape the ecological resources that fisheries depend upon. For example, the 'deadly trio' of oceanic warming, acidification and d...

Scientific Reports, 2021

Upwelling is a physical phenomenon that occurs globally along the eastern boundary of the ocean and supports pelagic fishery which is an important source of protein for the coastal population. Though upwelling and associated small pelagic fishery along the eastern Arabian Sea (EAS) is known to exist at least for the past six decades, our understanding of the factors controlling them are still elusive. Based on observation and data analysis we hypothesize that upwelling in the EAS during 2017 was modulated by freshwater-induced stratification. To validate this hypothesis, we examined 17 years of data from 2001 and show that inter-annual variability of freshwater influx indeed controls the upwelling in the EAS through stratification, a mechanism hitherto unexplored. The upper ocean stratification in turn is regulated by the fresh water influx through a combination of precipitation and river runoff. We further show that the oil sardine which is one of the dominant fish of the small pelagic fishery of the EAS varied inversely with stratification. Our study for the first time underscored the role of freshwater influx in regulating the coastal upwelling and upper ocean stratification controlling the regional pelagic fishery of the EAS. Upwelling is a physical process that brings cold and nutrient-rich subsurface waters to the upper ocean. This process makes the nutrient-deficit and sunlight-replete waters of the upper ocean biologically productive by kick-starting the organic carbon production by phytoplankton through photosynthesis. Consequently, upwelling regions of the world ocean are also regions of intense fishery activities 1. Though upwelling regions occupy only 5% of the total ocean area, it accounts for 25% of the global marine fish catch 2. Usually, eastern boundaries of the ocean are well known for coastal upwelling 3 and high chlorophyll a (Chl-a) concentrations, such as California, Peru and Chile coasts in the Pacific and West Africa (Canary upwelling) and SouthWest Africa (Benguela upwelling) in the Atlantic. The exception is the coastal upwelling along Somalia 4 and Arabia 5 in the Indian Ocean that occurs along the western boundary (Fig. 1). This is because the seasonal monsoon wind that blows in a south-westerly direction (summer or southwest monsoon) from June to September drives offshore Ekman transport supporting upwelling. The same southwest monsoon wind system also drives upwelling along the eastern Arabian Sea (EAS) 6,7 (Fig. 1). This makes the Arabian Sea a unique basin with seasonal upwelling occurring along both eastern and western boundaries. Though the magnitude of upwelling in the EAS is much smaller compared to the other eastern boundary upwelling regions, it supports a substantial pelagic fishery like oil sardine, mackerel, and anchovies 8-13 that supplements the nutrition requirement of the population in this region. In fact, the pelagic fishery from the EAS contributes to 20% of the total marine fish catch from India 14 , while the oil sardine alone accounts for 15% of the total marine fish landings of India 15. The regional oceanography of the EAS is unique 16 with semi-annually reversing winds and coastal currents 17 , upwelling driven phytoplankton bloom and primary production 6 , seasonal hypoxia 18 , intrusion of high and low salinity waters 19,20 , presence of coastal Kelvin wave and westward propagating Rossby wave 17 , and occurrence of warm pool 21. The coastal regions of the EAS receive substantial seasonal monsoon rainfall from June to September, which feeds the numerous small and medium rivers flowing through the coastal plain and joins

2013

from the effect of fishing. However, recent large investments in fishing capacity and navigation aids have led to fleets that now cover the world's ocean, including polar and deep, low-productivity areas, where catches are affecting easily depleted populations of long-lived species. The biomass of large pelagic fish in these areas taken by longlines, purse seines, and drift nets has also plummeted. Studies on available data have shown that deep-sea fisheries that collapsed in the 1970s have not recovered. Overfishing has negative impacts on marine biodiversity. The lowered biomasses and fragmented habitats resulting from the impacts of fishing have led to local extinctions, especially among large, long-lived, slow-growing species with narrow geographical ranges. In addition, the ability of the component ecosystems and their embedded species to withstand stresses resulting from climate change and other human impacts will be reduced, though direct demonstration of this effect may not be evident in many systems for some decades. Destructive practices such as trawling, dynamiting, and dredging change the structure of marine ecosystems, with consequential changes in their capacity to provide services, such as food provisioning and income generation. Longterm losses in species and habitats through destructive fishing ultimately reduce the biodiversity of these affected systems, resulting in a further loss of services such as coastal protection. Some systems may recover and improve the availability of some services and products fairly quickly; other more vulnerable systems, such as cold-water corals and seamounts, may take hundreds of years to recover. The implementation of no-take marine reserves combined with other interventions, such as controls on fishing capacity, would be a more proactive response to fisheries management than current reactive approaches. Marine reserves can contribute to better fisheries management-helping to rebuild stocks through enhanced recruitment and spill-over effects, maintaining biodiversity, buffering marine systems from human disturbances, and maintaining the ecosystems that fisheries rely on. Aquaculture is not a solution to the problem of declining wild-capture fisheries. Good governance and effective management of wild-capture fishing are likely to be more successful approaches. Farmed species such as salmon and tuna, which use fishmeal, may in fact contribute to the problem since much of the fishmeal and oil currently used in the aquaculture industry is derived from wild-caught small pelagic fish. In some countries, such as Chile, small pelagic fish that were once a source of cheap protein for people are now largely diverted for fishmeal. The supply of wild marine fish as a cheap source of protein for many countries is declining. Per capita fish consumption in developing countries (excluding China) has declined from 9.4 kilograms per person in 1985 to 9.2 kilograms in 1997. In some areas, fish prices for consumers have increased faster than the cost of living. Fish products are heavily traded, and approximately 50% of fish exports are from developing countries. Exports from developing countries and the Southern Hemisphere presently offset much of the demand shortfall in European, North American, and East Asian markets. The proposed future uses of marine systems pose significant policy challenges. Ocean ranching of marine organisms, bioprospecting, seabed mining, and carbon sequestration in deep ocean waters are foreseeable uses of marine systems. However, the potential impacts of these activities are not well known. In some cases no or only limited field studies have been conducted to test the theoretical basis for the activity. Policies will need to deal with the uncertainty of potential impacts and the limited understanding of marine biodiversity. National and regional ocean policies that incorporate zoning for various uses within an integrated ecosystem-based management framework are likely to be needed. Such policies might include marine protected areas that can contribute to the restoration of species and habitats and thus form part of a precautionary strategy for guarding against management errors. Central Gyres Food -human ** ** ** ** Food -animal ** ** Fiber, timber, fuel * * * Medicines, other services * Biodiversity ** ** * * Biological regulation Nutrient cycling and fertility * * * * Atmospheric and climate regulation * * * Human disease control Waste processing Flood/storm protection Employment ** ** * * Cultural and amenity ** Key: * some importance ** very important