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Cd Van Der Lingen - One of the best experts on this subject based on the ideXlab platform.
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Spatial variation in meristic and morphometric characteristics of sardine Sardinops Sagax around the coast of southern Africa
African Journal of Marine Science, 2019Co-Authors: G. Groenewald, Coleen L. Moloney, Cd Van Der LingenAbstract:Spatial variability in phenotypic characteristics within a fish population may be used to infer the existence of multiple stocks, and knowledge of the population structure of exploited species is important for their sustainable management. In this study we investigated geographic variability in meristic (vertebral count) and morphometric (body shape) characteristics of sardine Sardinops Sagax from three southern African regions: Namibia, the South African west coast, and the South African south coast. There were significant regional differences in vertebral counts, with Namibian fish tending to have more vertebrae than South African fish, but with no difference between sardine off the South African west and south coasts. Body shape was characterised using morphometric landmarks, and shape changes were investigated using geometric morphometrics, with influences on fish shape assessed using multivariate regressions. To remove the effects of allometry, the 22 shape variables (represented by Procrustes coordinates) were regressed against fish size (represented by centroid size). There was a significant allometric effect, which was removed by using the residuals of these regressions in further analyses. A multivariate multiple regression was applied to the 22 size-corrected shape variables and to three covariates: condition factor, stomach fullness and fat stage. The significant influence of these covariates was removed by using the residuals from this regression in a canonical variate analysis, where corrected shape variables were classified in relation to region, year and sex. The Mahalanobis distances from the canonical variate analysis differed significantly for most combinations of classifier variables, with clear separations among the three regions. Sardinops Sagax off Namibia had thicker bodies and more contracted tail regions than South African fish, whereas S. Sagax off the South African south coast had thinner bodies and smaller heads than those off the west coast. These results support the hypothesis of multiple sardine stocks around southern Africa.Keywords: body shape, canonical variate analysis, management, population structure, stock discrimination, vertebral count
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Spatial variability in branchial basket meristics and morphology of southern African sardine Sardinops Sagax
African Journal of Marine Science, 2016Co-Authors: Izwandy Idris, Coleen L. Moloney, Cd Van Der LingenAbstract:We examined spatial variability in meristic and morphological characteristics of the branchial basket of sardine Sardinops Sagax collected from four geographical regions around the southern African coast, namely Namibia and the South African west, south and east coasts. Our analysis tested the hypothesis of three putative sardine stocks off South Africa, one in each of the three geographical regions. We therefore collected fish data from Namibia to compare with South Africa, because sardine from the two countries are considered to be separate stocks. Morphometric measurements (gill arch length and gill raker spacing) and meristic data (number of gill rakers) were collected from the left side of the first gill arch from a total of 377 sardine, approximately equally divided between the regions. A multivariate general linear model with caudal length as covariate was used to assess differences among fish from the four regions and significant differences were observed, although not always consistently across a...
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Testing for the occurrence of pilchard herpesvirus (PHV) in South African sardine Sardinops Sagax
African Journal of Marine Science, 2016Co-Authors: Bm Macey, Kevin W. Christison, J De Goede, L Hutchings, Cd Van Der LingenAbstract:Catches of South African sardine Sardinops Sagax have declined in recent years from about 200 000 t harvested annually during the period 2002–2006 to less than 100 000 t. Consequently, some companies are now importing sardine from sources elsewhere in the world to meet local demand for canned sardine and bait. This importation has the potential for the introduction of sardine pathogens, in particular the pilchard herpesvirus (PHV), which could have a negative impact on the currently small South African sardine population. The aims of the current study were to determine whether PHV is present in the local sardine population and to assess the extent to which sardine is being imported into the country and whether imported fish are from countries where the virus is known to be endemic. Fish sampled from South Africa’s western (n = 150), southern (n = 182) and eastern (n = 96) putative stocks of S. Sagax were analysed for the presence of PHV using real-time quantitative polymerase chain reaction (qPCR). The or...
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Indicators of sustainable fishing for South African sardine Sardinops Sagax and anchovy Engraulis encrasicolus
African Journal of Marine Science, 2006Co-Authors: T. Fairweather, Cd Van Der Lingen, Anthony J. Booth, Laurent Drapeau, J. J. Van Der WesthuizenAbstract:Six indicators were investigated for South African sardine Sardinops Sagax and anchovy Engraulis encrasicolus: mean length of catch, length-at-50% maturity, total mortality, exploitation rate, ratio of bycatch, and centre of gravity of commercial catches. Sardine length-at-50% maturity is the most promising as a descriptive indicator because it is positively correlated with population size for an extensive time period (1953–2005). The remaining indicators were limited by shorter data-series (1984–2005). However, mean length of catch, ratio of bycatch and exploitation rate were found to be useful when considered in conjunction with other indicators. The centre of gravity of commercial sardine catches has shown a significant eastward shift from the West Coast, whereas that of anchovy has remained off that coast. Ratio of bycatch indicates that school composition is a reliable descriptive indicator of relative abundance in the two species. Fewer indicators for anchovy were useful, which is attributed to this...
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Density-dependent changes in reproductive parameters and condition of southern Benguela sardine Sardinops Sagax
African Journal of Marine Science, 2006Co-Authors: Cd Van Der Lingen, Pierre Fréon, T. Fairweather, J. J. Van Der WesthuizenAbstract:The sardine Sardinops Sagax population in the southern Benguela has undergone substantial fluctuations in size over the past 50 years, collapsing from an apparently large population in the 1950s to low levels in the mid-1960s, remaining low for the next two decades, and recovering from the late 1980s to a population size that is now similar to or larger than that which occurred during the 1950s. Marked changes in condition and reproductive parameters of sardine have also occurred during this period; condition and standardised gonad mass are higher and length-at-maturity is lower at low population size compared with high population size. The correspondence between the temporal patterns in condition, reproductive parameters and population size are strongly suggestive of density-dependence, and indicate a compensatory response arising from reduced intra-specific competition. This is likely to have resulted from greater per capita food intake, improved body condition and hence faster growth, thus enabling fis...
Carl D. Van Der Lingen - One of the best experts on this subject based on the ideXlab platform.
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Otolith δ18O and microstructure analyses provide further evidence of population structure in sardine Sardinops Sagax around South Africa
ICES Journal of Marine Science, 2020Co-Authors: Tatsuya Sakamoto, Carl D. Van Der Lingen, Kotaro Shirai, Toyoho Ishimura, Yonela Geja, James Peterson, Kosei KomatsuAbstract:Abstract Sardine Sardinops Sagax is an ecologically and economically important Clupeid found off the entire South African coast that includes both coastal upwelling and western boundary current systems. Although the management of the sardine fisheries historically assumed a single, panmictic population, the existence of three, semi-discrete subpopulations has recently been hypothesized. We conducted otolith δ18O and microstructure analyses to investigate nursery habitat temperatures and early life growth rates, respectively, of sardine collected from three biogeographic regions around South Africa’s coast to test that hypothesis. Analyses indicated that for both summer- and winter-captured adults and summer-captured juveniles, fishes from the west coast grew significantly slower in water that was several degrees cooler than those from the south and east coasts. This suggests that mixing of sardines between regions, particularly the west and other coasts, is relatively limited and supports the hypothesis of semi-discrete subpopulations. However, the west-south differences disappeared in the results for winter-captured juveniles, suggesting that differences in early life conditions between regions may change seasonally, and/or that all or most winter-captured juveniles originated from the west coast. Further elucidating the interactions between South African sardine subpopulations and the mechanisms thereof is important for sustainable harvesting of this species.
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Polyhalogenated Compounds (Halogenated Natural Products and POPs) in Sardine (Sardinops Sagax) from the South Atlantic and Indian Oceans.
Journal of Agricultural and Food Chemistry, 2020Co-Authors: Sarah Schlag, Carl D. Van Der Lingen, Ryan C. Uren, Hindrik Bouwman, Walter VetterAbstract:Halogenated natural products (HNPs) and persistent organic pollutants (POPs) were quantified in South African sardines (Sardinops Sagax) from one site in the South Atlantic Ocean and one in the Ind...
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stock discrimination of south african sardine Sardinops Sagax using a digenean parasite biological tag
Fisheries Research, 2015Co-Authors: Laura Frances Weston, Cecile Reed, Marc Hendricks, Henning Winker, Carl D. Van Der LingenAbstract:a b s t r a c t Spatial and temporal variation in infection of South African sardine, Sardinops Sagax, by a metacercar- ial parasite was examined to test the hypothesis that the South African sardine population comprises multiple stocks. Samples of adult S. Sagax were collected monthly from four commercial fishery land- ing harbours off the west and south coast and three indices of infection (infection prevalence, mean infection intensity and mean parasite abundance) were determined for each sample. Generalized linear models (GLMs) were used to assess the relative importance of putative stock (sardine caught off the west coast were assumed to be from the putative "western" stock whereas those caught off the south coast were assumed to be from the putative "southern" stock), season, year, fish size and all possible two-way interactions, where a binomial distribution was assumed for prevalence and a negative binomial distri- bution assumed for infection intensity and parasite abundance. The most parsimonious model for each index was selected based on Akaike's Information Criterion, and significant GLMs were derived for all three indices. Putative stock was the most significant contributor to explaining deviance seen in infection intensity and parasite abundance, and was the second most important contributor to explaining deviance seen in infection prevalence, with fish from the putative western stock having significantly (p < 0.001) higher parasite loads compared to those from the putative southern stock. Temporal variability was also observed, with season and year also contributing significantly to all three models. Despite this temporal variability, the marked spatial difference in the distribution of infection of S. Sagax by metacercariae sup- ports the hypothesis of western and southern stocks of sardine off the coast of South Africa. The presence of infected large sardine off the south coast indicates that these putative stocks are not discrete and that some degree of mixing occurs between them, at least from the western to the southern area.
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Incorporating parasite data in population structure studies of South African sardine Sardinops Sagax.
Parasitology, 2014Co-Authors: Carl D. Van Der Lingen, Laura Frances Weston, Nurudean Norman Ssempa, Cecile ReedAbstract:A multidisciplinary approach has been applied to examine the population structure of sardine Sardinops Sagax off South Africa, where this species supports significant fisheries and is also of ecological and eco-tourism importance. Observations of discontinuous sardine distribution patterns, discrete spawning grounds and significant spatial differences in a variety of phenotypic characteristics have suggested the existence of discrete western, southern and eastern sardine sub-populations or stocks. The use of parasites as biological tags to elucidate sardine population structure has recently been investigated, and strong spatial gradients around South Africa in the prevalence, mean infection intensity and mean abundance of a digenean 'tetracotyle' type metacercarial endoparasite considered to be of the genus Cardiocephaloides and found in the humours of fish eyes support and have proved particularly convincing evidence for the sardine multiple stock hypothesis. A discontinuous distribution in the occurrence of another parasite, the coccidean Eimeria sardinae found in fish testes, has provided additional but weaker evidence of discrete stocks. These results have contributed to a changed understanding of the population structure of South African sardine and have significant implications for management of the fisheries for this species.
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The effects of freezing on the morphometrics of sardine Sardinops Sagax (Jenyns, 1842)
Fisheries Research, 2010Co-Authors: Grea Wessels, Coleen L. Moloney, Carl D. Van Der LingenAbstract:Abstract The effects of freezing on the morphometrics of sardine Sardinops Sagax were studied. Results were variable depending on the length of the freezing period, but all fish showed significant ( p
Kevin Hill - One of the best experts on this subject based on the ideXlab platform.
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re assessment of the stock recruit and temperature recruit relationships for pacific sardine Sardinops Sagax
Canadian Journal of Fisheries and Aquatic Sciences, 2010Co-Authors: Sam Mcclatchie, Ralf Goericke, Guillermo Auadg Auad, Kevin HillAbstract:The harvest guideline for Pacific sardine (Sardinops Sagax) incorporates an environmental parameter based on averaged surface temperatures at the Scripps Institution of Oceanography pier (SIO pier) in La Jolla, California, USA, which would be invoked after a series of cool years to reduce commercial catches using a precautionary decision rule. We revisit the stock-recruit and temperature-recruit relationships underpinning the currently used environmental parameter for sardine assessment and found that the temperature-recruit relationship no longer holds for the SIO pier when time series are updated with data from more recent years. The significance of the correlation between temperature and recruitment was also artificially increased by autocorrelation in the time series. In contrast, the stock-recruit relationship was still valid when recent data were added. SIO pier surface temperatures are warmer than 10 m-depth Southern California Bight (SCB) temperatures where the sardine spawn, and the difference has increased since the late 1970s. Sardine recruitment was also not related to offshore temperatures in the SCB. We demonstrate that the environmental proxy derived from SIO pier tem- perature, which has never affected the harvest guideline since its implementation, no longer predicts recruitment of Pacific sardine, and should be removed from sardine management.
W. J. Fletcher - One of the best experts on this subject based on the ideXlab platform.
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Growth rate of larval Sardinops Sagax from ecosystems with different levels of productivity
Marine Biology, 2001Co-Authors: D. J. Gaughan, W. J. Fletcher, K. V. WhiteAbstract:Otolith increment data were used to age larval Sardinops Sagax from shelf waters between 118°E and 137°E off southern Australia. Maximum and mean growth rates up to an age of 30 days, estimated from a Laird–Gompertz model, were 0.62 and 0.48 mm day–1, respectively. The growth rate of larval S. Sagax from southern Australia was less than, or at most comparable to, those estimated from the substantially more productive upwelling systems of southwestern Africa, the central coasts of North and South America, and inshore of the Kuroshio system east of Japan. The lower productivity of the sardine habitat off southern Australia could be expected to manifest as fewer and/or less extensive patches of suitably dense plankton, or lower levels of sufficient food availability, which results in the lower growth rate of larvae. This probably causes higher mortality and, along with slower growth rates of post-recruit stages, may therefore contribute to the low stock size of sardines in southern Australia. Nonetheless, the similarities in growth rates of larvae within a single species over widely separated regions suggest such rates fall between predetermined bounds, limited by starvation at the lower end and an ontogenetic maximum at the other.
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The links between functionally distinct adult assemblages of Sardinops Sagax: larval advection across management boundaries
ICES Journal of Marine Science, 2001Co-Authors: D. J. Gaughan, K. V. White, W. J. FletcherAbstract:Otolith increment data were used to age larval Sardinops Sagax collected from shelf waters between Kangaroo Island in South Australia (SA) and Albany in Western Australia (WA). Distributions of both ages and hatch-dates were compared between six regions across this broad area to examine the hypothesis that larvae arising from spawning sardines in WA may be advected by the Leeuwin Current to the central coast of SA prior to metamorphosis. Current and wind data were analysed to estimate potential rates of passive transport. It appears likely that larvae arising from commercially exploited S. Sagax populations in WA can be passively transported close to the region of the S. Sagax fishery on the central coast of SA prior to metamorphosis. The potential for links between distant (>1000 km) management units requires reconsideration of the scale over which the population dynamics of southern Australian S. Sagax operate. This study provides an example of how information on larval dynamics, including the influences of oceanographic factors, gained from a relatively short period of field work (1 month) can significantly increase our understanding of population dynamics of exploited fish and subsequently have direct relevance to resource management. 2001 International Council for the Exploration of the Sea
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Spatial distribution of sardine (Sardinops Sagax) eggs and larvae : an application of geostatistics and resampling to survey data
Canadian Journal of Fisheries and Aquatic Sciences, 1999Co-Authors: W. J. Fletcher, Neil R SumnerAbstract:The abundance of eggs and larvae of sardine (pilchard) (Sardinops Sagax) off the south coast of Western Australia was investigated using geostatistical and bootstrap resampling techniques. A two-dimensional correlogram showed that the patch of newly spawned pilchard eggs had dimensions of 8 nautical miles (M) in diameter in the offshore direction and 10 M in the alongshore direction. For older stages, the size of the patch tended to increase and the level of cohesion decrease. It was more difficult to determine the size of the patch from directional variograms. The abundance of 1- and 2-day-old eggs in the study area was estimated using ordinary kriging. A bootstrapping analysis suggested that the optimal sampling design for day 1 eggs should use 4 × 10 M grids, an increase in intensity on the 5 × 15 M grids used in previous surveys.
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Use of the Daily Egg Production Method to Estimate the Stock Size of Western Australian Sardines (Sardinops Sagax).
Marine and Freshwater Research, 1996Co-Authors: W. J. Fletcher, E. A. Hayes, R. J. Tregonning, S. J. BlightAbstract:The daily egg production method was used to estimate the spawning biomass of the sardine Sardinops Sagax in the Albany region of Western Australia. Plankton surveys covering 10000 - 14000 km² were completed in July of 1991 and 1992 in three to five days using up to three boats. Adult sardines were obtained from the local purse-seine fleet. The spawning area was similar in both years at approximately 3800 km² (1100 nmile²), but the number of eggs collected was larger in 1991 with egg production values of 6.5 per 0.05 m2 day-1 compared with 3.9 per 0.05 m2 day-1 in 1992. The average batch fecundity values were similar (approximately 11000 eggs female-1) as were the proportions spawning (0.13 in 1991; 0.09 in 1992). The calculated biomass estimates were 23 121 t (CV = 0.51) and 16 121 t (CV = 0.44) in 1991 and 1992 respectively.
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Validity of Using Translucent Zones of Otoliths to Age the Pilchard Sardinops Sagax neopilchardus from Albany, Western Australia
Marine and Freshwater Research, 1996Co-Authors: W. J. Fletcher, S. J. BlightAbstract:Otoliths (sagittae) of the pilchard (Sardinops Sagax neopilchardus) from the Albany region of Western Australia were examined on a monthly basis during 1989 to 1991. When read consecutively, with the month of capture known, a clear annual cycle of an increase in marginal increments to October followed by a decline was recorded. This pattern was, however, severely distorted when samples were re-examined after having been jumbled and the month of capture concealed. Younger age groups (≤3) showed evidence of multiple rings being formed annually, but not in all years or individuals, and this was not evident in older individuals (≥4). Agreement between readings was low (43-53%), especially between different readers. Resultant growth curves showed that males grow to a smaller size (L∞ =164, K = 0.805, Φ = 1.03) than females (L∞ = 174, K = 0.584, Φ= 0.95). Agreement between counts of annuli and ages estimated by using otolith weight and length was only 54% for all individuals, but increased to 76% for individuals assigned the same age by different readers. Given the poorer predictions of future catch rates from the relative number of 2-year-olds in the commercial catch using annuli (implying lower accuracy) and increased complexity in preparation, otolith weights will be the method adopted for future ageing.
Mónica Hernández-rodríguez - One of the best experts on this subject based on the ideXlab platform.
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Critical thermal maxima and minima of Sardinops Sagax caeruleus Girard 1854 and the analyses of behavioral responses to establish adequate endpoints
Tropical Zoology, 2010Co-Authors: Marcel Martínez-porchas, Mónica Hernández-rodríguezAbstract:Endpoint responses identifying critical thermal maximum (CTMax) and minimum (CTMin) temperatures of the Pacific sardine Sardinops Sagax caeruleus Girard 1854 were estimated, after acclimation to a summer (SC) and a winter (WC) thermal cycle, to establish a precise endpoint for this species. The initial response observed during critical thermal limits was the onset of muscle spasms (OS) which was followed by loss of equilibrium (LE). Significant differences were found between SC and WC acclimated sardines when LE was used as the CTM endpoint. No differences were observed when the OS endpoint was used, owing to the high variance of OS values. Sardines had a CTMax of 30.4 and 31.8 °C for fish that underwent the WC and SC, respectively, while the CTMin was 5.2 and 6.5 °C for WC and SC sardines, respectively. Sardines showed a marked tolerance to low temperatures and some capacity to modify their critical limits when acclimated to different cycling thermal regimes. The thermal limits can be useful to compare sub-populations of this species inhabiting the North Pacific Ocean. Moreover, loss of equilibrium (LE) was a more consistent response than onset of spasms (OS); thus, it can be used as a reliable endpoint in further studies.
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Estimación de los rangos térmicos asociados con la distribución de Sardinops Sagax caeruleus, con base en su preferencia térmica Estimation of the thermal ranges associated with the distribution of Sardinops Sagax caeruleus, based on its thermal pref
2010Co-Authors: Marcel Martínez-porchas, Mónica Hernández-rodríguez, Educación Superior De EnsenadaAbstract:The Pacific sardine (Sardinops Sagax caeruleus) from Ensenada, Mexico, was exposed to two thermal regimes, cold (CR:13-18°C) and warm (WR:18-23°C) for 20 days. The thermal preference was studied using a gradient of temperatures, recording the preferred and avoided sites by the sardine. No significant differences among acclimation thermal regimes were observed for thermal preference. However, there was some difference for avoided temperatures showed by these two groups of sardine; 13.3-19.3°C was for CR and 16.9-22.3°C for WR. These results suggest that the studied sardine are able to survive within a thermal environment from 13.3 to 22.3°C, which shifts in the area delimited by San Francisco and Magdalena Bay.
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Estimación de los rangos térmicos asociados con la distribución de Sardinops Sagax caeruleus, con base en su preferencia térmica
Revista de biología marina y oceanografía, 2010Co-Authors: Marcel Martínez-porchas, Mónica Hernández-rodríguezAbstract:The Pacific sardine (Sardinops Sagax caeruleus) from Ensenada, Mexico, was exposed to two thermal regimes, cold (CR:13-18°C) and warm (WR:18-23°C) for 20 days. The thermal preference was studied using a gradient of temperatures, recording the preferred and avoided sites by the sardine. No significant differences among acclimation thermal regimes were observed for thermal preference. However, there was some difference for avoided temperatures showed by these two groups of sardine; 13.3-19.3°C was for CR and 16.9-22.3°C for WR. These results suggest that the studied sardine are able to survive within a thermal environment from 13.3 to 22.3°C, which shifts in the area delimited by San Francisco and Magdalena Bay.
