M. H. Griffiths

M. H. Griffiths
Ministry for Primary Industries · Directorate of Fisheries Science

Doctor of Philosophy

About

42
Publications
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Publications

Publications (42)
Article
Full-text available
Demography and life-history characteristics of reef fishes may vary as a consequence of ecological and environmental factors that lead to changes among populations. We evaluated variation in life-history traits in the leatherjacket Meuschenia scaber (Monacanthidae) through age-based analysis of 2112 fish collected from three locations in New Zealan...
Presentation
Full-text available
Species of the family Monacanthidae are found in both temperate and tropical waters, and support growing fisheries in both the Indo-Pacific and Atlantic. In general, monacan-thids are characterised by a relatively short lifespan and indeterminate growth patterns, but the life history parameters of most species are poorly understood. Additional inte...
Poster
Full-text available
The leatherjacket Meuschenia scaber is widely distributed in Australasian waters and was added to the New Zealand Quota Management System in 2003. The Ministry for Primary Industry (MPI) of New Zealand recognises leatherjacket as a priority for research because of the lack of data on its biology (e.g. growth rate, longevity, and reproduction) and t...
Article
Full-text available
The leatherjacket Meuschenia scaber is widely distributed in Australasian waters, and is a valued bycatch of inshore bottom trawl fisheries although little is known of its life history. Here, we describe the reproductive biology of the species based on 651 leatherjackets sampled in the Hauraki Gulf, New Zealand, between July 2014 and March 2016. Th...
Article
The effect of temporal variation in growth rate on per-recruit model outputs was investigated by comparing biological reference points obtained using growth curves derived for Umbrina robinsoni populations from False Bay, on the south coast of South Africa, sampled 10 years apart (1991–1993 and 2001–2003), and applying the two different age–length...
Article
Slender baardman Umbrina robinsoni are an important component of recreational shore-angler and spearfisher catches along the eastern seaboard of South Africa. Stocks of U. robinsoni at three sites—False Bay, Stil Bay and the KwaZulu-Natal (KZN) coast—were modelled using a per-recruit approach. Total (Z) and fishing (F) mortality rates were estimate...
Article
Biological data for Umbrina robinsoni were obtained from fish sampled monthly during 2001–2002 by shore-angling in the warm-temperate De Hoop Marine Protected Area (MPA) (n = 312), and by means of spearfishing during three trips (May, September and January 2001–2002) in the Kosi Bay region of the subtropical Maputaland MPA (n = 354). Annuli in otol...
Article
The stomach contents of 391 juvenile dusky kob Argyrosomus japonicus (23–805 mm total length, TL) from the Great Fish River estuary were analysed. Early juveniles (<50 mm TL) fed predominantly on mysids and calanoid copepods. As the juveniles increased in size, copepods were replaced by teleost prey, but mysids remained an important dietary compone...
Article
The sagittal otoliths of Lophius upsicephalus, although extremely variable in shape, were found to be the only structures suitable for age estimation. The annuli are multi-ringed zones separated by "wider than normal" opaque zones. They are difficult to interpret, especially those of fish older than nine years. Periodicity of annulus formation coul...
Article
The ages of dusky kob Argyrosomus japonicus, sampled from three regions along the South African eastern seaboard during 1991 and 1992, were determined from longitudinal sections of otoliths. The otoliths were selected from fish 35 – 1 750 mm total length. Ages from 0 to 42 years were recorded, but fish older than 27 were rare. Analysis of the otoli...
Article
Adult emigration and larval dispersal of carpenter Argyrozona argyrozona from the Tsitsikamma National Park (TNP), South Africa, were investigated using mark-recapture data and Acoustic Doppler Current Profiler measurements of currents. Tagging data showed that adult carpenter were mainly resident, with a small proportion (7%) leaving the TNP in bo...
Article
Spatial and temporal variation in the diet and feeding intensity of snoek, Thyrsites atun, a top predator of the southern Benguela, was investigated to provide information on data requirements for accuracy of annual diets as inputs to ecosystem models. Appropriate sample sizes to produce accurate daily or event-scale diet descriptions were investig...
Article
It has long been accepted that snoek Thyrsites atun in the Benguela system constitute a single stock that undergoes seasonal longshore migration in waters between southern Angola and the west coast of South Africa. Based on a review of past literature and evaluation of new data, it is contended that Benguela snoek exist rather as two separate sub-p...
Article
Fishery independent biomass surveys and commercial linefish catch returns were used to elucidate the spatial patterns of carpenter Argyrozona argyrozona distributed along the South African continental shelf. Two distinct areas of abundan ce ere determined, one on the central and the other on the eastern Agulhas Bank. Tagging studies revealed little...
Article
Two Umbrina species, U. canariensis Valenciennes 1843 and U. robinsoni Gilchrist and Thompson 1908, are recognised from southern Africa. The latter species was hitherto believed to be a synonym of Umbrina ronchus Valenciennes 1843 (type locality Canary Islands). U. canariensis is distributed along the South Africa eastern seaboard from Cape Point t...
Article
Full-text available
Carpenter Argyrozona argyrozona is an endemic sparid that constitutes an important component of the South African linefishery between Cape Agulhas and Port Alfred, where it exists as two stocks; one on the central Agulhas Bank and the other on the eastern Agulhas Bank. Spawner biomass-per-recruit (SB/R), fecundity-per-recruit (Egg/R) and yield-per-...
Chapter
IntroductionManagement of the South African marine line fisheryBiological assessment and regulationsInstitutional framework and the decision-making processComplianceCost of managementImpacts of the recreational line fisheryConclusions
Article
Umbrina canariensis were sampled from two disjunct regions of abundance off the South African east coast – the central Agulhas Bank (n = 227) and Algoa Bay (n = 550) – from March 2001 through February 2003. Marginal increment analyses supported annual deposition of growth zones in sagittal otoliths. Ages recorded using thin otolith sections were 2–...
Article
Growth rates of dusky kob Argyrosomus japonicus calculated from mark-recapture and otolith-reading methods were compared. Mark-recapture data showed that A. japonicus are resident in an area between the Breede River Estuary and Cape Agulhas on the south-east coast of South Africa. Maximum recapture length was 1 150mm. A von Bertalanffy growth curve...
Article
Full-text available
In order to determine the minimum sample size required to accurately estimate growth and mortality, and to assess the effects of using either random or stratified sampling procedures, a large sample of Argyrozona argyrozona (n = 618) was collected during February and March 1998 from the central Agulhas bank. To investigate the influence of monthly...
Article
Full-text available
Estimates of fish-community size spectra are promising indicators of the impact of fishing on fish assemblages. Size spectra consist of logarithmic graphs of abundance plotted against fish body size. Size spectra may either be constructed from length frequency data or estimated from the mean sizes and abundances of the species in an assemblage — ve...
Article
Full-text available
The carpenter seabream (Argyrozona argyrozona), known as "carpenter" regionally, is an endemic South Afri- can sparid found between St Helena Bay and KwaZulu-Natal (Fig.1) (Smith and Heemstra, 1986). Although the third most important species in the line-fishery in terms of landed mass, catch per unit of effort (CPUE) on traditional fishing grounds,...
Article
Full-text available
Within the context of an ecosystem approach for fisheries, there is a need for quantitative information on distributions of key marine species. This information is valuable input for modelling species interactions in the southern Benguela ecosystem. In the present study, a method is described for mapping the density distribution of 15 key species:...
Article
Full-text available
The 2001 Reykjavík Declaration on Responsible Fisheries in the Marine Ecosystem and the Plan of Implementation of the 2002 World Summit on Sustainable Development highlighted the need in fisheries to look beyond considering only the target species and to consider in fisheries management the impacts of fishing on the ecosystem as a whole, as well as...
Article
Full-text available
A dataset of linefish catch, effort and fish size distribution records has been assembled from archives to cover three short periods over the 100 years from 1897 to 1998 in four regions of the former Cape Colony, South Africa. Linefish catch and effort have increased several-fold over the period. Aggregate catch per unit effort (cpue) declined by m...
Article
Full-text available
Argyrozona argyrozona is an important component of the South African commercial linefishery. The purpose of this study was to develop a reliable protocol for estimating age and calculating growth. Methods based on both otoliths and mark-recapture data were investigated. Transverse sagittal sections from the Tsitsikamma National Park (TNP) showed cl...
Article
Full-text available
This review provides a historical overview of human activities in the Benguela and documents their effects on marine animal life. Considered are the activities of conventional industrial and inshore fisheries but also nonfishery activities, such as mariculture, regulation of river flow, introduction of marine invasive species, marine contruction an...
Article
Snoek (Thyrsites atun) is a valuable commercial species and an important predator of small pelagic fishes in the Benguela ecosystem. The South African population attains 50% sexual maturity at a fork length of ca.73.0 cm (3 years). Spawning occurs offshore during winter-spring, along the shelf break (150-400 m) of the western Agulhas Bank and the S...
Article
Fishery-dependent and fishery-independent distribution analyses together reveal four discrete areas of white stumpnose Rhabdosargus globiceps abundance between Port Nolloth and the Kei River off the Cape Province of South Africa: the Western Cape (Saldanha Bay), the South-Western Cape, the Southern Cape and the South-Eastern Cape. On the basis of m...
Article
Full-text available
The southern African coastline is dominated by strong currents. Along the eastern seaboard, the warm western boundary Agulhas Current sweeps close inshore along the shelf edge before diverging from the coast on the Agulhas Bank and retroflecting back into the Indian Ocean. On the western seaboard, strong jet currents develop in the southern Benguel...
Article
Movements of five warm-temperate, sparid reef fishes were studied on South Africa’s Agulhas Bank by mark–recapture. A small proportion (7.4%) of recaptured Petrus rupestris had moved distances of 200–1000 km towards adult aggregations along the east coast. Movement patterns of non-migratory P. rupestris and the other four species were, in spite of...
Article
The South African boat-based linefishery is a multi-species fishery with participants broadly divided into commercial (approximately 3000 vessels) and recreational (at least 4000 vessels) components. Atractoscion aequidens is an important species which, owing to a migratory lifestyle, is targeted by commercial communities throughout its estimated 2...
Article
The Cape commercial linefishery, established during the first half of the 19th century, currently consists of about 2 500 vessels (±20 000 crew), which land some 15 500 tons of fish each year. In spite of a long history, a lack of a long-term catch and effort data series has severely hindered the management of the fishery. This paper providcs comme...
Article
The dusky kob Argyrosomus japonicus is an important linefish species that is abundant in South African waters between Cape Agulhas and the Moçambique border. The juveniles (Y/R) and spawner biomass-per-recruit (SB/R) models were applied to the South African dusky kob stock, with accommodation for different inshore (Finshore) and offshore (Foffshore...
Article
The feeding ecology of dusky kob A. japonicus was determined from the stomach contents of line-caught specimens from several estuarine, surf zone and nearshore localities in KwaZulu-Natal and the Eastern and Western Cape. The accuracy of dietary descriptions for dusky kob depends on sample size, sampling frequency and sampling period. A. japonicus...
Article
Argyrosomus inodorus is an important linefish species off the eastern seaboard of South Africa, where it comprises three discrete stocks. Per-recruit models indicate that all three stocks are exploited far beyond optimal (FSB40 and F0.1) and threshold (FSB25) fishing limits, and that spawner biomass-per-recruit () ratios were 2.9–12.5%(SB/R)F = 0....
Article
Fishery dependent and fishery independent distribution analyses together reveal that there are three discrete areas of Argyrosomus inodorus abundance between Cape Point and the Kei River: one in the southeastern Cape, one in the southern Cape, and one in the southwestern Cape. On the basis of migratory patterns determined from tagging and catch dat...
Article
The life history of Argyrosomus japonicus off the east coast of South Africa was studied using biological, size composition and tagging data from fish caught in the estuaries, surf zone and nearshore marine environment of three coastal regions. Capture methods included hook and line (all habitats), seine-netting (estuaries and surf zone), and gill-...
Article
Silver kob Argyrosomus inodorus sampled from three regions along the South African southern and eastern seaboard during 1991–1992 were aged using frontal otolith sections. Otoliths (n = 750) were selected from fish ranging between 60 and 1 310 mm total length. Ages of 0–25 years were recorded, but fish older than 13 years were uncommon. Marginal in...
Article
East coast geelbek exist as a single stock comprising three distinct age/size structured subpopulations. The subadults (1-4 years) occur in the SW Cape, South Africa. They feed principally on anchovy Engraulis capensis, which they follow inshore in summer and offshore in winter. The adults (5-9+ years) undergo a seasonal inshore and longshore migra...

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Project (1)
Project
The aim of my PhD project are to estimate the parameters for models of growth (i.e., length at age), variability of length at age, length-weight relationship, natural mortality rate (M), and proportion mature at length or age in the New Zealand leatherjacket, Meuschenia scaber.