Marine Protected Areas (MPAs), the Ecosystem Approach to Fisheries management (EAF) and Integrated Coastal Management (ICM) have been identified as possible alternatives to traditional linefish ...management measures, which have largely failed. Monitoring and assessment of fish communities on a long-term basis is necessary, and will provide a means to evaluate the effectiveness of such management measures. Therefore, standardised protocols and optimal sampling methods for long-term monitoring (LTM) and assessment of coastal fish communities are essential. This study aimed to identify suitable methods and develop a protocol for assessment of inshore reef fish communities. A suitable location for evaluation of proposed methods was identified in the warm temperate biogeographical region of South Africa, encompassing the well-established Tsitsikamma Coastal National Park MPA and an adjacent exploited area. Chrysoblephus laticeps (roman) was identified as an indicator species for the study, as it has been well-studied and is well represented in the area. Underwater visual census (UVC) and controlled fishing were identified as suitable methods. UVC transects were found to be superior to point counts, in terms of sampling efficiency, variability, bias and required sample size. An effort of two angler hours per fishing station was shown to provide low catch variability, while at the same time a representative catch and low overall cost and required time. The methods were incorporated in a proposed sampling protocol, and evaluated. The methods were able to detect known differences between protected and exploited communities. It is recommended that LTM within protected areas, for detection of natural change, be focused on community-level indicators, while LTM in exploited areas, aimed at detection of anthropogenic change, be focused on species-level indicators. The proposed protocol with standardised methods will allow for comparisons across a network of LTM sites and provide the opportunity for a broad-scale assessment of the effects of environmental variables on reef fish stocks. The protocol developed in this study has application in other biogeographical regions in South Africa, and other parts of the world. Shift in the focus of much marine research, in South Africa and elsewhere, to LTM, highlights the relevance and timeous nature of this study.
White steenbras Lithognathus lithognathus (Pisces: Sparidae) has been a major target species of numerous fisheries in South Africa, since the late 19th century. Historically, it contributed ...substantially to annual catches in commercial net fisheries, and became dominant in recreational shore catches in the latter half of the 20th century. However, overexploitation in both sectors resulted in severe declines in abundance. The ultimate collapse of the stock by the end of the last century, and the failure of traditional management measures to protect the species indicate that a new management approach for this species is necessary. The species was identified as a priority for research, management and conservation in a National Linefish Status Report. Despite knowledge on aspects of its biology and life history, little is known about juvenile habitat use patterns, home range dynamics and movement behaviour in estuaries. Similarly, the movement and migration of larger juveniles and adults in the marine environment are poorly understood. Furthermore, there is a complete lack of information on its genetic stock structure. Such information is essential for effective management of a fishery species. This thesis aimed to address the gaps in the understanding of white steenbras movement patterns and genetic stock structure, and provide an assessment of its current conservation status. The study adopted a multidisciplinary approach, incorporating a range of methods and drawing on available information, including published literature, unpublished reports and data from long-term monitoring programmes. Acoustic telemetry, conducted in a range of estuaries, showed high site fidelity, restricted area use, small home ranges relative to the size of the estuary, and a high level of residency within estuaries at the early juvenile life stage. Behaviour within estuaries was dominated by station-keeping, superimposed by a strong diel behaviour, presumably based on feeding and/or predator avoidance, with individuals entering the shallow littoral zone at night to feed, and seeking refuge in the deeper channel areas during the daytime. Conventional dart tagging and recapture data from four ongoing, long-term coastal fish tagging projects, spread throughout the distribution of this species, indicated high levels of residency in the surf zone at the late juvenile and sub-adult life stages. Consequently, juvenile and sub-adult white steenbras are vulnerable to localised depletion, although they can be effectively protected by suitably positioned estuarine protected areas (EPAs) and marine protected areas (MPAs), respectively. It has been hypothesized that adult white steenbras undertake large-scale coastal migrations between summer aggregation areas and winter spawning grounds. The scale of observed coastal movements was correlated with fish size (and age), with larger fish undertaking considerably longer-distance coastal movements than smaller individuals, supporting this hypothesis. Given the migratory behaviour of adults, and indications that limited spawning habitat exists, MPAs designed to protect white steenbras during the adult life stage should encompass all known spawning aggregation sites. The fishery is plagued by problems such as low compliance and low enforcement capacity, and alternative management measures, such as seasonal closure, need to be evaluated. Despite considerable conventional dart tagging effort around the coastline (5 782 fish tagged) with 292 recaptures there remains a lack of empirical evidence of fish migrating long distances (> 600 km) between aggregation and spawning areas. This uncertainty in the level of connectivity among coastal regions was addressed using mitochondrial DNA sequencing and genotyping of microsatellite repeat loci in the nuclear genome, which showed no evidence of major geographic barriers to gene flow in this species. Samples collected throughout the white steenbras core distribution showed high genetic diversity, low genetic differentiation and no evidence of isolation by distance or localised spawning. Although historically dominant in several fisheries, analysis of long-term commercial and recreational catch data for white steenbras indicated considerable declines and ultimately stock collapse. Improved catch-per-unit-effort in two large MPAs subsequent to closure confirmed that MPAs can be effective for the protection of white steenbras. However, the current MPA network encompasses a low proportion of sandy shoreline, for which white steenbras exhibits an affinity. Many MPAs do not prohibit recreational shore angling, which currently accounts for the greatest proportion of the total annual catch. Furthermore, EPAs within the juvenile distribution protect a negligible proportion of the total available surface area of estuaries – habitat on which white steenbras is wholly dependent. Despite some evidence of recent increases in abundance in estuaries and the surf zone in certain areas, white steenbras meets the criteria for “Endangered” on the IUCN Red List of Threatened Species, and for “Protected species” status on the National Environmental Management: Biodiversity Act of South Africa. The species requires improved management, with consideration for its life-history style, estuarine dependency, surf zone residency, predictable spawning migrations and its poor conservation status. The multidisciplinary approach provides valuable information towards an improved scientific basis for the management of white steenbras and a framework for research that can be adopted for other overexploited, estuarine-associated coastal fishery species.
The first chapter provides a sketch of the background, education and career of Henry Burghersh, with an outline of the diocesan administration during his episcopate. The evidence of his registers ...suggests that his political career only took him away from his diocesan duties between 1327-1330 and 1334-1340, and even then the employment of vicars-general, and the development of the powers of the sequestrator ensured that the diocesan administration continued to run smoothly. In a study of the benefices of the diocese, a calculation is made of their total number in 1320 and of the relative proportions of rectories, vicarages and curacies. Ordinations of vicarages, portions of churches, and dependent chapelries are examined. An analysis, based on the Taxatio of 1291, is made of the relative values of benefices. An examination of the patronage of benefices reveals that ecclesiastical patrons outnumbered the laity by two to one. Ecclesiastical patrons consisted largely of religious houses, mainly those of the Benedictine and Augustinian orders, the secular clergy holding comparatively few advowsons. Among the laity, most patronage was held by the smaller landowners. The problems posed by divided advowsons, and the effects of `occasional' patronage, are discussed. By means of two samples (the first an analysis of all institutions made during the episcopate, and the second a more detailed biographical sample) the beneficed clergy of the diocese are studied. Their provenance is found to be mainly local; nearly two-fifths spent some time at a university, and the majority were already priests at the time of their institution. The procedure for admission to a benefice is examined. Length of tenure is discussed, and the impact of exchanges is assessed. It is suggested that, although non-residence affected nearly half of the beneficed clergy, its extent was controlled through the issue of fixed-term licences.
Okefenokee Swamp is a mosaic of dynamically related vegetation patches which represent different stages of temporal succession. This mosaic is continually changing from within as patches undergo ...succession. In the absence of disturbances, succession generally proceeds from open marsh to either cypress or shrub swamp then to either climax broad-leaved evergreen or mixed hardwood swamp. Patches within the vegetation mosaic are created by localized disturbances such as fire and logging. Severe burns are spotty in Okefenokee but can kill all or most vegetation in a given area. Post-fire communities generally resemble earlier successional stages. Secondary succession will recapitulate the original successional development and eventually restore approximate pre-fire floristic composition. Most fires, however, are light surface fires which tend to maintain existing vegetation communities and thereby arrest the process of succession. Logging operations removed over 90% of the merchantable cypress in Okefenokee Swamp. Most logged areas are now dominated by climax mixed hardwood or broad-leaved evergreen swamps, a transition historically prevented by recurrent fires. Re-establishment of cypress is not, in general, evident and return to pre-logging floristic composition is unlikely even if frequent severe fires occur. Characteristics of the Okefenokee vegetation mosaic are therefore determined by the intensity, frequency, and spatial distribution of disturbances which create patches versus the direction and rate of patch succession following disturbances. The relative lack of "climax" vegetation patches in Okefenokee indicates disturbances, primarily fires, are frequent relative to the rate of plant succession. The result of this recurrent disturbance regime is maintenance of a heterogeneous, disclimax ecosystem. If the disturbance regime under which a plant community evolved is altered or if the community is subjected to disturbances it has never encountered, then the behavior and structure of that community may change. Such changes in the Okefenokee Swamp are evident in logged areas. Modification of the recurrent fire regime could also result in permanent alteration of many of the unique characteristics of Okefenokee Swamp that its inclusion in the National Wilderness System and National Refuge System was designed to preserve.
Characterising performance of environmental models Bennett, Neil D.; Croke, Barry F.W.; Guariso, Giorgio ...
Environmental modelling & software : with environment data news,
02/2013, Letnik:
40
Journal Article
Recenzirano
Odprti dostop
In order to use environmental models effectively for management and decision-making, it is vital to establish an appropriate level of confidence in their performance. This paper reviews techniques ...available across various fields for characterising the performance of environmental models with focus on numerical, graphical and qualitative methods. General classes of direct value comparison, coupling real and modelled values, preserving data patterns, indirect metrics based on parameter values, and data transformations are discussed. In practice environmental modelling requires the use and implementation of workflows that combine several methods, tailored to the model purpose and dependent upon the data and information available. A five-step procedure for performance evaluation of models is suggested, with the key elements including: (i) (re)assessment of the model's aim, scale and scope; (ii) characterisation of the data for calibration and testing; (iii) visual and other analysis to detect under- or non-modelled behaviour and to gain an overview of overall performance; (iv) selection of basic performance criteria; and (v) consideration of more advanced methods to handle problems such as systematic divergence between modelled and observed values.
► Numerical, graphical and qualitative methods for characterising performance of environmental models are reviewed. ► A structured, iterative workflow that combines several evaluation methods is suggested. ► Selection of methods must be tailored to the model scope and purpose, and quality of data and information available.
