Sexual size dimorphism in calanoid copepods (Centropagidae) from Patagonia (Argentina)

Calanoid copepods of the genus Boeckella and Parabroteas (P. sarsi) are dominant in zooplankton communities of Patagonian lakes and ponds. This study addresses the occurrence of sexual size dimorphism in calanoid copepods of the genus Boeckella and in the monospecific genus Parabroteas occurring in 12 lakes and ponds of Patagonia (Argentina). The morphometric analysis performed showed that in all the species studied the female is larger than the male, although the difference in size among sexes was found to be variable between species. Interestingly, all species showed significant intraspecific stability in their sexual size dimorphism despite potential differences in their environments regarding predation pressure, environmental stability (permanent or temporary waters) and altitude distribution of populations. Finally, we discuss the potential implications of sexual dimorphism in terms of resource use and vulnerability to predation among other environmental forces which may play a role in promoting larger female to male size.     

Trends in exploitation, development and management of artisanal mud crab (Scylla serrata-Forsskal-1775) fishery and small-scale culture in Kenya: An overview

Mud crab (Scylla serrata) is a delicacy for subsistence consumption in fisher communities and tourist hotels in the coast of Kenya while export demand to markets in China and Japan is expanding and provides competitively higher prices. Crab exploitation and degradation of the mangrove forests have increased over the last decades therefore threatening the capture fishery. The preferred market size crab has consistently decreased from more than 1 kg two decades ago to the current size of 0.5 kg therefore posing both management and livelihood threat to the critical ecosystem (mangrove) and coastal populations. To meet the increased tourist and export demand and provide surplus for the local community while conserving the critical crab ecosystem, small-scale aquaculture has been initiated in the concept of silvofisheries. Initial culture methods have targeted sub-adult crabs of 150–350 g for culture to market size (>0.5 kg) in drive-in cages and pens (mud crab fattening). These technology attained survival of between 50 and 70% and a market price of 5 dollars per kilogram. However, research is ongoing to assess viability of stocking juvenile seed crabs directly in ponds as practised in South East Asia (SEA) as opposed to stocking of sub-adults in drive-in cages. In comparison with other areas, crab capture fisheries in East Africa have limited management and enforcement frameworks/capabilities within the wider regional fisheries policies. Also there is limited understanding of wild mud crab resources and suitable management options to avoid over-exploitation as observed in SEA. The double-edged demand (wild market size capture and juvenile capture for aquaculture) for mud crabs in addition to mangrove degradation are likely to cause great challenges to stock exploitation and livelihoods of the coastal people dependent on the resource. This review paper provides an inside onto the tradition, trends and options for development of mud crab capture and culture in Kenya.     

An evaluation of artificial shelters in the artisanal spiny lobster fishery in Gazi Bay,Kenya

Two designs of artificial shelters were evaluated for use in the artisanal spiny-lobster fishery in Gazi Bay, Kenya. Both types of shelter were effective in aggregating the spiny lobster Panulirus ornatus in nearshore sea-grass beds. Lobsters aggregated at the shelters were caught by free-diving fishermen, using spearguns and hand nets. Mean lobster catches taken from the shelters ranged from 0,38 to 0,83 kg·trip^?1, around 50% of those taken farther offshore in natural reefs. No significant difference was found in the size or sex composition between shelter and reef-caught lobsters.     

Spatial distribution of Illex argentinus in San Matias Gulf (Northern Patagonia,Argentina) in relation to environmental variables: A contribution to the new interpretation of the population structuring

Traditionally, it was assumed that major spawning activity of Illex argentinus occurs in discrete pulses along the outer-shelf/slope off Argentina/southern Brazil during late-fall/winter and that early life stages develop near the Brazil–Malvinas Confluence (BMC). However, a novel hypothesis of the population structuring of the species was proposed that states that coastal waters may be important as spawning and feeding grounds. Here, we analyzed the spatial distribution of Illex argentinus inside San Matias Gulf based on the position of the CPUE of jiggers in order to improve the knowledge of the population structuring in coastal regions. Squids were mainly concentrated on the northern region of the gulf where favorable oceanographic conditions (e.g. water stratification, chlorophyll-a concentration peaks) to feeding and spawning are present. These results provided empirical evidences that individuals of I. argentinus use Argentinean coastal waters, particularly San Matias Gulf, as permanent feeding and spawning grounds which supports the new hypothesis.     

Participatory artisanal fisheries management in islands: Application to the Canary Islands (Spain)

Socio-economic development of small-island fishing communities is greatly dependent on local coastal and marine resources. However, illegal fishing and aggressive practices in insular ecosystems lead to over-exploitation and environmental deterioration. Moreover, a lack of scientific data increases uncertainty and prevents the adequate monitoring of marine resources. This paper focuses on the integration of local fishing communities into decision-making processes with the aim of promoting artisanal fishing on the Island of Tenerife (the Canary Islands), as a way to preserve the marine ecosystem and socio-economic development of traditional cofradias (fishers' organisations). A qualitative methodological framework, based on participatory problem-solution trees and focus groups, was used to identify the main factors impeding the sustainable development of the artisanal fishing sector on the island and to elaborate collective proposals with policy implications. The fishing community involved identified four main issues that are maintaining an unsustainable island fishery: 1) Over-exploitation; 2) Poor self-management of cofradias and commercialisation problems; 3) Fisher individualism and low co-management strategies, and 4) Illegal fishing increase vs. artisanal fishing decline. Results show the required policy enhancements to tackle them and the need to adapt regulations to the local situation.     

Diagenetic model of the Bajo Barreal formation (Cretaceous) in the southwestern flank of the Golfo de San Jorge Basin (Patagonia, Argentina)

This paper analyses the diagenetic evolution of sandstones belonging to the Bajo Barreal Formation (Cretaceous) in the Golfo de San Jorge Basin (Patagonia, Argentina). The Bajo Barreal Formation includes the main reservoirs, which are located along the western area of the basin and is composed of sandstones, conglomerates, mudstones, tuffaceous mudstones and some layers of tuffs. The principal reservoirs comprise medium-to coarse-grained sandstones, which are dominated by feldspathic litharenites and contain minor amounts of litharenites and lithic arkoses. The authigenic minerals include kaolinite, smectite, chlorite, quartz overgrowths, microquartz and calcite, with minor proportions of megaquartz, siderite, analcime, laumontite, feldspar overgrowths and illite/smectite and chlorite/smectite mixed layers. Secondary porosity is much more important than primary porosity and is produced by the dissolution of feldspar, lithic clasts and clay cements. The diagenetic history of the Bajo Barreal sandstones can be divided into seven diagenetic stages, each of which is characterized by a specific assemblage of authigenic minerals and diagenetic processes. Eogenetic conditions occur in stages 1, 2, 3 and 4. Stage 1 corresponds to shallow burial characterized by the physical reduction of primary porosity by compaction; during stage 2, rim clay cements of chlorite, smectite and clinoptilolite, as well as thin quartz overgrowths, were formed. The precipitation of pore-filling cements of kaolinite, chlorite and smectite occurred during stage 3, while stage 4 records the intense dissolution of feldspar, lithic fragments and kaolinite cements. Mesogenesis occurs in diagenetic stages 5 and 6. The former corresponds to a new phase of authigenic kaolinite, while the latter records the significant dissolution of feldspar, lithic clasts and previous cements, which produced the highest values of secondary porosity. Finally, stage 7 corresponds to the highest degree of diagenesis in the Bajo Barreal Formation (mesogenesis), which resulted in the precipitation of cements of zeolites and calcite, as well as quartz and plagioclase overgrowths.     

Linking fishery management and conservation in a tropical estuarine lagoon: biological and physical effects of an artisanal fishing gear

Information coming from fishery monitoring, surveys and experimental fishing with participation of fishers was employed to determine the impact of an artisanal gear, ‘boliche’, on the biodiversity of the Ciénaga Grande de Santa Marta (CGSM), an estuarine lagoon on the Caribbean coast of Colombia. Fishery monitoring (catch data) included landings before (1968 and 1978) and after (1994–1996) the introduction of the boliche in the CGSM (1985), whereas surveys were conducted seasonally during 1993–1994. Fishing experiments involved evaluating different mesh sizes and the short-term effect of physical disturbance by the boliche. Monitoring suggested potential trophic effects of this fishing gear: the catch of large, long-lived, carnivorous species declined after the introduction of the boliche in the CGSM, whereas catch rates of smaller, shorter-lived, and lower trophic level species increased. Surveys revealed that the boliche retained 41 species. The by-catch made up 62% of the total catch and the remaining 38% involved the three target species Eugerres plumieri, Mugil incilis and Cathorops spixii. Selectivity experiments showed that 2.5 in. stretched mesh size gill nets caught more species than the 3.0-in. mesh. The smaller mesh also increased the risk of a critical reduction in the spawning stock of target species (notably E. plumieri); a situation that could affect the fish community if mesh sizes lower than 2.5 in. were intensively used. Suspended particulate matter significantly increased after fishing activity, with higher resuspension on mud-shells and mud substrata, whereas dissolved oxygen showed no appreciable changes after fishing operations. Notwithstanding, the activity of the boliche would generate sediment resuspension between 382 and 470 t day⁻¹, which could lead to potential cascade impacts on water quality. We propose a framework of redundancy in management measures in order to simultaneously reach management and conservation goals.     

Accounting for indirect effects and non-commensurate values in ecosystem based fishery management (EBFM)

Ecosystem-based fishery management (EBFM) requires taking account of indirect effects (such as habitat destruction, incidental mortality, and competition between the fishery and marine mammals or birds) and dealing with non-commensurate values (such as yield from the fishery and production of offspring by the birds or mammals competing for the same resource). The perspective of EBFM requires that the rate of fishing mortality is less than the value that provides maximum sustainable yield (MSY), but the question is how far below this level should the fishery operate? For this problem in multiobjective programming, simple method of solution was developed and illustrated with the fishery for sandeels (Ammodytes spp.) in the Shetland Islands. The yield from the fishery at a given fishing mortality F is scaled by MSY (so that this quantity increases as fishing mortality increases from 0 to that giving MSY) and the breeding success of predators (black-legged kittiwakes Rissa tridactyla and Arctic terns Sterna paradisaea) at a given fishing mortality is scaled by that in the absence of fishing. The result is two non-dimensional quantities that can be combined into a single value function, which can then be explored or optimized. It is shown that a reduction of only about 20 percent in yield can nearly double the breeding performance of the more sensitive predator. Extensions of the method are discussed; these include the use of maximum economic yield (MEY) and state dependent life history, as implemented by stochastic dynamic programming.     

Socio-economic,operational and technical characterisation of the harvesting of gooseneck barnacle (Pollicipes pollicipes) in SW Portugal: Insights towards fishery co-management

The present study characterised the socio-economic, operational and technical aspects of harvesting the gooseneck barnacle (Pollicipes pollicipes) along the southwestern coast of Portugal. For this purpose, face-to-face interviews were conducted with commercial harvesters of the two most representative fishery associations (covering 51% licensed harvesters) in the area of the Parque Natural do Sudoeste Alentejano e Costa Vicentina. Based on traditional ecological knowledge, this study confirmed the local importance, ancestral character and family traditions of this activity, which constitutes the exclusive occupation of nearly half of the interviewed harvesters and an important source for household incomes. In addition, data was also gathered on preferential fishing zones, harvesting effort and duration, daily catches and selling prices. The main concerns, problems and difficulties experienced in this activity relate to the excessive number of recreational harvesters, creating problems at the levels of exploitation, commercialisation, management and inspection. The study further confirms the rising interest and involvement of the commercial harvesters in enhancing the competences of the local fishery associations. In particular, local harvesters want to encourage the development of a co-management system comprising spatial-temporal measures to avoid conflicts of use over space and resources, as well as innovative marketing strategies to improve the recognition, value and traceability of the shellfish. Overall, the information gathered is most valuable for adopting an alternative approach based on the cooperation and co-responsibility at local and regional levels, involving the stakeholders in the proposal of management measures adapted to the specificities of this area, activity and resource.     

Factors contributing to effective management in the Sakuraebi (Sergia lucens) fishery of Donggang,Taiwan

An in-depth assessment was conducted on the functioning of a Taiwanese Sakuraebi (Sergia lucens) fishery management institution to understand the role of leadership in the context of long-term incentive creation. Interviews with relevant stakeholders and statistical analysis of fisheries data indicated that the daily vessel quota system and fishers’ collective efforts to influence the market resulted in increased sales value, while simultaneously allowing for the equitable distribution of benefits from the Sakuraebi fishery in Donggang, Taiwan. Local fishers expressed a high level of satisfaction with the corresponding activities initiated by the fisher's organization. Interview respondents felt that promotional marketing activities led by the organization to enhance domestic consumption were particularly effective, and statistical analysis suggests that these activities helped to reduce the dependency of Taiwanese Sakuraebi fishers on export markets. A notable characteristic of this fishery is that it combines a large-scale sales organization, which enables the exertion of market influence, with a small-sized subsidiary organization for fisheries management. An annually rotating leadership system for managing fishery operations also provides members with the opportunity to share a sense of participation and responsibility, while keeping long-term policy goals. This study reinforces previous findings that leadership, social cohesion, and the nature of the resource are key factors determining the effectiveness and success of fisheries management.     

History,effort distribution and landings in an artisanal bottom longline fishery: An empirical study from the North Atlantic Ocean

Commercial fishing data were used to reconstruct historical spatio-temporal patterns of fishing effort and landings in the bottom longline fishery of the Azores. Key events during an important 15-year period were charted, through fisher interviews together with GIS analysis. While effort distribution varied over time, the prevailing pattern was a shift in focus from eastern to western areas and from shelf/slope to offshore banks and seamounts in response to policy measures (e.g. banning bottom longline inside 3 NM, public aids for modernization of the fleet) and reduced fishing yields. Areas 12–50 NM from shore represented the most vital fishing grounds in terms of fishing effort and production. Declining landings of the major demersal species, in recent years, indicate that present catch levels are not sustainable and further measures need to be taken in order to sustain fisheries resources. Knowledge of fleet behavior and the distribution of fishing effort, particularly in patchy environments, provide valuable insights into the impacts of past management decisions and help predict the outcome of new policies both in this region and elsewhere.     

Population dynamics and fishery management of the paua,Haliotis iris

A population model is developed and used in conjunction with the results of a study of an unexploited population of paua (Haliotis iris Martyn) to examine the historical pattern of recruitment and yield per recruit. As H. iris cannot yet be aged, the population model uses size rather than age classes, but is structurally similar to the Leslie matrix model. Simulations suggest that the observed population size structure resulted from a short (about 5 year) period of high recruitment, preceded and followed by longer periods of low recruitment. Yield per recruit analysis shows that the present minimum legal size for the fishery (127 mm) provides close to the maximum yield per recruit for most stocks, although yield per recruit could be increased in some areas by a reduction in minimum legal size.     

Evolution of operational management procedures for the South African West Coast rock lobster (Jasus lalandii) fishery

The commercial fishery for Jasus lalandii, the South Africa West Coast rock lobster, began in the late 1800s and at its peak in the early 1950s yielded an annual catch of 18 000 t. Although this annual catch has dropped to only some 2000 t over recent years, the fishery remains South Africa's third most valuable for landed value. The primary reason for the low total allowable catch (TAC) over these recent years has been a marked drop in somatic growth rate that occurred at the end of the 1980s, for reasons that remain unexplained. A key problem in formulating TAC recommendations with longer‐term objectives in mind, has been uncertainties about likely future trends, particularly in somatic growth and recruitment. To address this problem, an “operational management procedure” (OMP) was adopted in 1997 and has twice been re‐evaluated and modified (in 2000 and 2003) in the light of further data and changing perceptions of resource dynamics. The history of this process is reviewed, concentrating on the most recent modification. In particular, a summary is given of the process by which the merits of alternative management procedures were evaluated over a range of important uncertainties about the dynamics of the resource. This summary includes a discussion of the key trade‐offs between resource rebuilding, future TAC trends and TAC variability, and the eventual choice that was made. The paper concludes by listing a number of lessons learnt concerning best practice for OMP development as this process evolved.     

Development policies,state interventions and struggles for livelihood rights in coastal communities in Kerala,India: A case study of the Cochin clam fishery

One of the major dilemmas of using rural commons for industrial uses in developing countries relates to the failure of the state to evolve consensus on allocating property rights to local communities and modern enterprises in a manner that sustains livelihoods and ecosystems. While traditional coastal communities enforce customary rights for fishing and mineral mining, the state sometimes reallocates traditional fishing territories to commercial mining to facilitate rapid industrialization. Communities oppose such transfers because of the negative impacts of commercial dredging on traditional fishing and ecosystems. Based on detailed field level surveys conducted in 2004, this paper describes how rural island communities along Cochin estuary expressed their opposition to the transfer of clam-mining rights to industries by democratic social mobilization. Counter moves were collectively organized by modern enterprises and trade unions which had the support of the state. However, major political parties retreated from conflict management, leaving the matter in a state of flux. This paper suggests that the state must recognize traditional livelihood rights of communities if it is to resolve conflicts and ensure the sustainable and equitable use of natural resources.