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Assessing the suitability of commercial fisheries data for local-scale marine spatial planning in South Africa ab
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R Chalmers , A Oosthuizen , A Götz
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, A Paterson & WHH Sauer
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Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, South Africa b
South African Institute for Aquatic Biodiversity, Grahamstown, South Africa
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Park Planning and Development, South African National Parks, Nelson Mandela Metropolitan University (NMMU), Port Elizabeth, South Africa d
Elwandle Node, South African Environmental Observation Network (SAEON), Grahamstown, South Africa e
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Zoology Department, NMMU, Port Elizabeth, South Africa Published online: 23 Dec 2014.
To cite this article: R Chalmers, A Oosthuizen, A Götz, A Paterson & WHH Sauer (2014) Assessing the suitability of commercial fisheries data for local-scale marine spatial planning in South Africa, African Journal of Marine Science, 36:4, 467-480, DOI: 10.2989/1814232X.2014.979228 To link to this article: http://dx.doi.org/10.2989/1814232X.2014.979228
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AFRICAN JOURNAL OF MARINE SCIENCE ISSN 1814-232X EISSN 1814-2338 http://dx.doi.org/10.2989/1814232X.2014.979228
Assessing the suitability of commercial fisheries data for local-scale marine spatial planning in South Africa R Chalmers1,2*, A Oosthuizen3,5, A Götz1,4,5, A Paterson2 and WHH Sauer1 Department of Ichthyology and Fisheries Science, Rhodes University, Grahamstown, South Africa South African Institute for Aquatic Biodiversity, Grahamstown, South Africa 3 Park Planning and Development, South African National Parks, Nelson Mandela Metropolitan University (NMMU), Port Elizabeth, South Africa 4 Elwandle Node, South African Environmental Observation Network (SAEON), Grahamstown, South Africa 5 Zoology Department, NMMU, Port Elizabeth, South Africa * Corresponding author, e-mail:
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This study integrates fisheries logbook data with observer and vessel monitoring system (VMS) data in order to assess the accuracy of reported data and to develop high-resolution spatial data suitable for use in local-scale marine spatial planning analyses. Spatial assessments were conducted on five nearshore commercial fisheries to provide baseline information to inform spatial management and conservation planning in Algoa Bay, South Africa. Clear spatial patterns in the distribution of fishing effort were apparent for the linefishery, chokka-squid and inshore demersal trawl sectors. Observer and VMS data confirmed the broad spatial distribution of resource-use patterns of logbook data. Combining these data sources allowed higher-resolution spatial indices of fishing effort to be developed, which are suitable for systematic spatial planning on a local scale and can be used for future spatial management and conservation. Keywords: chokka-squid, conservation planning, demersal trawl, linefish, logbooks, observer data, shark longline, small pelagic, vessel monitoring system
Introduction Commercial fisheries are a primary driver of change in marine ecosystems (Nelson 2005), affecting the abundance and distribution of target and non-target species, and altering marine habitats. This is evident through studies that report globally declining landings of wild capture fisheries (Griffiths 2000; Rosenberg 2003; Pauly 2008), collapse of stocks (Myers et al. 1997; Attwood and Farquhar 1999; Jackson et al. 2001; Mullon et al. 2005) and ecosystem degradation as a result of destructive fishing techniques (Kaiser et al. 1998; Thrush et al. 1998; Thrush and Dayton 2002; Hinz et al. 2009). Understanding the spatial and temporal patterns of fisheries activities is critical for management, spatial planning of extractive use and conservation of marine resources (Halpern et al. 2008). Despite commercial fisheries data being available for most sectors, they are often not accessible at suitable spatial resolution or in a useable format. Coastal management and conservation efforts are increasingly being undertaken on local scales. However, commercial fisheries data collection and analyses are typically undertaken on a national scale and a sectoral basis (Griffiths 2000; Rademeyer et al. 2008) with little regard for local-level requirements, or the cumulative impacts resulting from multiple sectors (Guerry 2005; Curtin and Prellezo 2010). Spatial planning is integral to managing a diverse range of activities and is key to improving management
and conservation of coastal resources (Douvere 2008), but requires high-resolution spatial data for fisheries and other activities in order to be effective on a local scale (Richardson et al. 2006). Detailed local-scale spatial analyses of commercial fisheries are critical for understanding patterns in resource use, and how they have changed in response to past management interventions or to changes in the distribution and abundance of target stocks. The incorporation of high-resolution fisheries data into the planning and design process has been shown to reduce substantially the displacement of fisheries (Richardson et al. 2006). This information is becoming increasingly important for spatial management where fisheries and conservation efforts are in conflict over the use of resources within small, spatially defined areas (e.g. where important fishing grounds overlap with biodiversity hotspots). Synthesising and presenting complex fisheries data in a format that aids in understanding the competing interests of different user groups improves the transparency of the planning process, and facilitates decision-making. Catch-landing information from commercial logbooks is a commonly used source of fishery information for management (Cotter and Pilling 2007). The accuracy of logbook information, however, can be questionable (Lee et al. 2010), because it is dependent on the honesty of each fisher and on their dedication to maintaining accurate records.
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Furthermore, most commercial sectors operate over large areas and report catch and effort using low-resolution grids (i.e. 5′, 10′ or 20′ grids) that are of limited use for local-level planning that requires high-resolution spatial information (Lee et al. 2010). Integrating commercial logbook data with observer and vessel monitoring system (VMS) data sources provides a means to assess the spatial accuracy of the logbook data (Gerritsen and Lordan 2011). Observer programmes and VMS provide information on fisheries activities that is independent of potential reporting biases by the fishers themselves. Observer programmes are designed to collect information on fishing effort, catch composition and weight, as well as spatial information on catch or fishing location. Onboard observer programmes obtain this information for fisheries that utilise larger vessels and spend extended periods of time at sea. However, access-point monitoring is used in fisheries where vessels are small and fishing trips are short. This allows only for the assessment of landings; the spatial information provided by skippers cannot be assessed. Systems such as VMS are integral components of monitoring, control and surveillance (MCS) programmes, and allow regulatory authorities to track the identity, position, heading and speed of vessels remotely (Lee et al. 2010). This information can be used to infer fishing activities, thereby providing an independent means to assess the spatial accuracy of reported logbook data, and is being used increasingly for research and monitoring purposes (Witt and Godley 2007; Bastardie et al. 2010; Lee et al. 2010; Gerritsen and Lordan 2011). In this paper, the spatial patterns of five nearshore commercial fisheries in Algoa Bay, on the south-east coast of South Africa (Figure 1), are reviewed using logbook, observer and VMS data sources. We aim to provide scientists, managers and fishery rights-holders with information to inform marine spatial planning initiatives currently under way in Algoa Bay. Furthermore, fisheries logbook data are assessed against observer and VMS data to determine the spatial accuracy of reported information and to assess the efficacy of using these data in marine spatial planning. This study presents an approach that is applicable to potential future marine conservation and systematic planning studies in South Africa. Material and methods Descriptions of the fisheries Commercial linefishery The South African commercial linefishery is a multispecies hook-and-line fishery that mainly uses skiboats with twin outboard motors; these vessels are of variable length (6–10 m) and crew size. The first management framework and data collection system was implemented in 1985 (van der Elst and Garratt 1984; van der Elst and Penney 1995; Penney et al. 1997), yet, owing to the limited scientific information available for most species, the regulations were ineffective at restricting catch (Attwood and Bennett 1995; Brouwer et al. 1997; Penney et al. 1997), resulting in the depletion of most stocks, and a state of emergency being declared in 2000 (DEAT 2000). This led to a reduction in effort from approximately 3 000 vessels at the end of the 20th century (Griffiths 2000; Mann 2000) to 450 vessels
Chalmers, Oosthuizen, Götz, Paterson and Sauer
during the medium- and long-term-rights allocation process from 2003–2006 and to more restrictive bag and size limits being implemented in 2005 (Mann 2013). Chokka-squid jig fishery Chokka-squid Loligo reynaudii was a bycatch species landed in the trawl sector (Augustyn et al. 1992). Exclusion of foreign trawling and the development of an overseas market led to the formalisation of a highly selective jig-handline fishery in the mid-1980s (Augustyn 1990; Sauer et al. 1992). Small twin-outboard skiboats were replaced by larger deck-boats (>20 m) with onboard freezer facilities, in order to improve the quality of the product. The fishery is managed by a total allowable effort (TAE) (Sauer 1995; Augustyn and Roel 1998) with a seasonal closure imposed for a variable length of time over summer to protect dense aggregations on the inshore spawning grounds. There is no restriction on vessel movement; however, the stocks are distributed primarily in the Eastern Cape, resulting in the sector being of considerable socio-economic importance to the provincial economy (Sauer et al. 2003). The TAE was set at 138 vessels for the period 2006–2013, following a long-term-rights allocation process (DEAT 2006a). Small-pelagic purse-seine fishery This fishery targets small, short-lived fish species, mainly sardine Sardinops sagax and anchovy Engraulis encrasicolus (DEAT 2005a). The national fleet comprises approximately 100 vessels that have no spatial restrictions on movement along the coastline. However, effort is focused primarily along the Western Cape coast with only a small portion of the fleet being based in the Eastern Cape, where it fishes predominantly local waters. Inshore demersal trawl fishery This fishery targets two main species; the shallowwater hake Merluccius capensis and the East Coast sole Austroglossus pectoralis (DEAT 2005b, 2006b). The inshore fleet consists of approximately 35 vessels which are permitted to trawl within 20 nautical miles of the coastline and shallower than 110 m, and are subject to size, power and gear restrictions (DEAT 2005b). Coastal embayments along the south-east coast are closed to trawling. Onboard freezing facilities are limited and trips are therefore of only a few days’ duration (Wilkinson and Japp 2005). Illegal targeting of bycatch species is a concern (DEAT 2005b). Demersal shark longline fishery Directed longline permits for the targeting of sharks were first introduced in the early 1990s (Japp 1999), and were subsequently separated into demersal and pelagic sectors in 2005 (Clarke and Smith 2007). The sector utilises weighted bottom-set gear in coastal waters (
