Harvesting Pressures Research Articles

REDUCING THE RISK OF FISHERY RESOURCE DISASTERS: A BIOECONOMIC APPROACH TO SUSTAINABLE RESOURCE MANAGEMENT1

Abstract: Recognition is growing that fisheries must be both ecologically and commercially sustainable. The bioeconomic models proposed herein constitute an analytic framework capable of integrating the ethics and Societal values associated with fisheries preservation. Specifically, we focus on the normalized optimal (equilibrium) fish population, z*, a dimensionless variable representing biomass as a proportion of environmental capacity. We model z* as a function of (a) the dimensionless “bionomic growth ratio”, γ, which is the ratio of the discount rate to the intrinsic population growth rate, and (b) the preservation coefficient, Ω, which is the ratio of the preservation value (a measure of Society's value for the stock) to price, assuming that the population growth rate and intrinsic growth rate are fixed. It is shown that increasing Ω significantly impacts z*, particularly for moderate values of γ (2 γ 4). Finally, stochastic population models are used to analyze the risk of a fish stock collapse due to harvesting pressures. The bioeconomic models and simulations herein described improve the accuracy and reliability of maximum sustainable yield management.

Sustainable management of Canada’s boreal forests: Progress and prospects

:The last decade of innovation in forest management in Canada is reviewed. Institutions such as the Sustainable Forest Management Network and Canada’s Model Forest Program have attempted to develop a better understanding of ecological disturbance patterns and processes. Additional research has explored socio-economic dimensions of sustainable forestry, such as ways to incorporate the aspirations of indigenous peoples, build community capacity, and facilitate forest certification. The most promising innovations tend to have both environmental benefits (sustaining non-timber values) and economic benefits (reducing costs and sustaining future timber values), making their implementation more likely. Some on-theground examples of “win-win” solutions at stand and landscape levels in Canada’s boreal forests include: patch retention in conjunction with the creation of large cutblocks; protection of advance regeneration during timber harvesting; promotion and prediction of natural regeneration; various approaches to mixedwood (broadleaf and conifer) management; avoidance of unnecessary brush control; extended rotations and selection management for some tree species and stand types; promoting the flow of fibre to its highest value uses; and zoning in support of intensive silviculture, thereby potentially reducing harvesting pressures from lands with high conservation value. More closely emulating natural patterns of forest disturbance and forest recovery can help sustain biodiversity and ecosystem services, but may not generate all values desired from managed forests. Further research is needed to calibrate indicators of ecological sustainability. Institutional and policy innovation must also be evaluated in the context of adaptive management to improve the effectiveness of forestry practices and nurture the social license for the utilization and management of public forests.

The Social Context For Harvesting Iriartea deltoidea (Arecaceae)

Iriartea deltoidea grows abundantly from Nicaragua to Bolivia. The stem is harvested for construction, furniture making, and handicrafts. The objective of my study was to understand the potential for sustainable harvesting of this palm. Ethnographic fieldwork about market patterns and decision-making among harvesters revealed the nature of harvesting pressures near settled areas. The study also demonstrates methods for assessing social and economic influences on harvesting.

Local Management of Mangrove Forests in the Philippines: Successful Conservation or Efficient Resource Exploitation?

Recent environmental “narratives” suggest that local people are effective stewards of forest resources. Local restoration and management of mangrove forests, in particular, are now widely advocated as a solution to achieve both economic and environmental conservation goals. This paper presents findings from a study of 2 coastal sites in the Philippines that are renowned and often showcased as success stories in community-based, mangrove reforestation and management. These cases are especially intriguing because local tree planting and management emerged in both areas long before governments and nongovernment organizations began to promote such activities. These management systems are a successful economic innovation in that planted mangroves protect homes and fish pond dykes from wave and wind damage, and the production of high-value construction wood is dramatically enhanced through intensive plantation management. Mangrove plantations are an efficient alternative to harvesting from unplanted, natural mangroves and their spread may reduce harvesting pressures on existing forests. However, mangrove plantations are structurally and compositionaly very different from unplanted forests, a finding of particular concern given that such plantations are increasingly encroaching into and replacing natural forests. Furthermore, planted forests are not typically viewed by planters in terms of their environmental conservation values and are frequently cut and cleared to make space for alternative uses, especially fish farming and residential settlement. The suggestion that these local mangrove management systems are successful for conservation thus needs to be qualified.

The effects of selective logging on forest structure and tree species composition in a Central African forest: implications for management of conservation areas

The forests of Central Africa enjoy world-wide recognition for their spectacular wildlife and also harbor an abundance of high quality timber. With mismanagement and the conversion of large tracts of West African forest to agricultural production, Central African forests are experiencing increased harvesting pressures. This is particularly true for species of African mahogany ( Entandrophragma spp.). In the tri-national region of Cameroon, Central African Republic, and Republic of Congo, a widely applied version of the Integrated Conservation and Development Model attributes the dual management objectives of biodiversity conservation and timber production to the same zones. Many conservationists working in the region believe that highly selective timber extraction is the best management scenario to meet these objectives. Conventional wisdom holds that if selective logging does not adequately regenerate Entandrophragma spp., loggers will quit the region after having mined the forest. A comparison between unlogged, 6-month and 18-year post-harvest forest stands indicates lasting effects of highly selective, high grade logging. While there was little difference in tree species composition and diversity between treatments, stem densities of both saplings and trees in unlogged forest were significantly higher than those in forest sampled 18 years after logging. Evidence suggests inadequate recruitment of Entandrophragma cylindricum and E. utile, the principal timber species, to justify continued timber extraction. Data indicate a significant shift in canopy dominance from shade intolerant to shade bearing species due to insufficient canopy disturbance. Nevertheless, an abundance of other top quality timber species remains after selective removal of African mahogany and these forests will remain attractive to loggers long after the elimination of Entandrophragma spp. A better approach to manage timber zones for timber production and conservation would be an adaptive management approach based on increased species selection and canopy disturbance. Zones targeting the conservation of closed forest obligate species should not be logged.

Arapaima: An Amazonian fish species of immense proportions

The Arapaima (Arapaima gigas), the largest freshwater fish in the world, is coming under increasing threat from a deluge of modern economic pressures. Dying traditional management practices, increased harvesting pressures, habitat destruction, and the seemingly insurmountable challenges for enforcing and managing the interior fisheries of the Amazon present an uncertain future for this species. In the face of a cultural reshaping, indigenous communities in the interior of Guyana, South America are partnering with the Iwokrama International Center for Rain Forest Conservation and Development and the Guyanese government, to stem the immediate onslaught and establish a long-term strategy for sustainable community-based management of the fish. Peer-reviewed article accepted for publication on 15 January 2002.

The Distribution and Production of the Hard Clam, Mercenaria mercenaria, in Wassaw Sound, Georgia

Hard clams,Mercenaria mercenaria, occurred in four intertidal habitats in the outer, high salinity (18‰) region of Wassaw Sound, Georgia: small feeder creeks\((\bar x = 36 per m^2 )\); oyster shell bar deposits\((\bar x = 31 per m^2 )\); headwaters of shelly, sandy-mud, sand, and mud bottom creeks (\(\bar x\) = 26, 19, 13 and 3 per m2, respectively); and among live oysters (\(\bar x\) = 1 per m2). 0266 03 Clams from creek bottoms were larger (\(\bar x\) = 7.3 cm) than those from intertidal flats (\(\bar x\) = 4.7 cm) due to differences in predation or harvesting pressures, not to differeing rates of recruitment. Juveniles were absent from most areas, possibly because of increased juvenile mortality, natural sporadic settling, or restricted gonadal development due to abnormally low spring salinity from 1977 through 1979. Clams from Little Tybee Island, where sediments are sandy-mud, had faster growth rates than those from North Cabbage and Wassaw Islands, where clam beds were in shell deposits. Clams older than 7 years dominated at Wassaw and Little Tybee Islands (64 and 71%, respectively) and younger clams dominated (82%) at North Cabbage Island. These differences in age class structures are attributed to different harvesting or predation pressures. Clams from Little Tybee and Wassaw Islands occurred in creek bottoms, whereas clams from North Cabbage Island occurred on an intertidal flat in the open sound. Also, a greater variety of clam predators and greater densities ofUrosalpinx cinerea andBusycon spp. occur on intertidal flats of the open sound than on creek bottoms. Net reproduction ofMercenaria was 7.7 g ash-free dry weight (AFDW) per m2 per yr at Little Tybee Island, 6 g AFWD per m2 yr at Wassaw Island and 2.7 g AFDW per m2 per yr at North Cabbage Island. Differences are attributed to differences in standing stocks, age class structure, and growth rate. Standing stocks were low (11 g AFDW per m2) at North Cabbage, moderate at Little Tybee (50 g AFWD per m2) and high (120 g AFDW per m2) at Wassaw Island. The turnover ratios (P/B) of Wassaw, Little Tybee, and North Cabbage Island populations were low (0.05, 0.14, and 0.23, respectively) because a high percentage of older (>7 years) clams make up the populations.

Effects of Harvesting Aquatic Bait Species from a Small West Virginia Stream

Abstract The potential impact of commercial bait harvest from small streams was studied in Rich Creek, West Virginia. A mail survey and personal interviews of bait dealers in the mountain areas of this state established typical harvest pressures exerted by commercial operations. Bait fish and crayfish in 50-m sections of Rich Creek were harvested three times every two weeks from May 15 until September 15, 1973, via seine and minnow traps. Treatments consisted of no harvest, a harvest simulating a typical bait dealer, and a harvest pressure twice that of a commercial dealer; all treatments were in triplicate. The effects of the harvests were determined by comparisons over time within treatments, comparisons between treatments and comparisons with final population indices. No significant differences in these comparisons were found to occur for the bait species or for the game fish species inhabiting the study sections. The different harvesting pressures did not appear to affect the densities of the bait and...