Life history of the dusky kob<i>Argyrosomus japonicus</i>(Sciaenidae) off the east coast of South Africa

Griffiths, Matthew

doi:10.2989/025776196784158653

Cited by 100 publications

(108 citation statements)

References 15 publications

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“…Machado-Schiaffino et al, 2010). In the case of South African kob species, spawning migrations of adults is more prevalent in dusky-than silver kob, although common breeding areas may occur in the southern and south-eastern regions (Griffiths, 1996b(Griffiths, , 1997b. Silver kob distribution is "locked" between that of dusky kob (Indian Ocean) and west coast dusky kob (A. coronus) (Atlantic Ocean) (Potts et al, 2010), following adaptation to colder waters compared with the other two species.…”

Section: Resultsmentioning

confidence: 99%

“…Given the fact that dusky kob attain sexual maturity at a much larger size than silver kob (Griffiths, 1996b(Griffiths, , 1997b and that drumming muscles are used during courtship in sciaenid species (Griffiths, 1997c), unidirectional hybridization could be explained by hypothesizing that large dusky kob males may occasionally out-compete silver kob males by gaining access to oestrous silver kob females. Griffiths (1996b) found that sexually mature dusky kob males (but not females) could be found throughout the distribution range of the species in South African waters and Griffiths (1997b) reported a tendency for silver kob to have a skewed sex-ratio in favour of females, which could result in increased opportunities for dusky kob males to compete with silver kob males. This could take place in areas where species-ratios are skewed such as overlapping inshore/estuarine habitat, as it is the case between silver kob and west coast dusky kob in estuaries of the south-western African coast, where the former seems to outcompete the latter (Lamberth et al, 2008).…”

Section: Squaretailmentioning

confidence: 99%

“…Silver kob (Argyrosomus inodorus) and dusky kob (A. japonicus) are two large sciaenid fish species that partly co-occur along southern coasts of South Africa, from False Bay in the Western Cape province (Atlantic Ocean) to the Kei River in the Eastern Cape Province (Indian Ocean) (Griffiths, 1996b(Griffiths, , 1997b. Silver-and dusky kob have been identified as distinct species since 1995, following an in depth study of habitat distribution, morphometrics, otolith and anatomical structure (Griffiths and Heemstra, 1995).…”

Section: Introductionmentioning

confidence: 99%

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Identification of naturally occurring hybrids between two overexploited sciaenid species along the South African coast

Mirimin¹,

Kerwath²,

Macey³

et al. 2014

Molecular Phylogenetics and Evolution

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Hybridization between fish species can play a significant role in evolutionary processes and can influence management and conservation planning, however, this phenomenon has been widely understudied, especially in marine organisms. The distribution limits of two sciaenid species (silver kob, Argyrosomus inodorus, and dusky kob, A. japonicus) partly overlap along the South African coast, where both species have undergone severe depletion due to overfishing. Following the identification of a number of possible cases of species misidentification or hybridization (21 out of 422 individuals), nuclear and mitochondrial DNA data (12 microsatellite loci and 562 bp of the COI gene) were analysed to investigate the genetic composition of these individuals. Results indicated a field-based species misidentification rate of approximately 2.8% and a rate of natural hybridization of 0.7%. Interestingly, all hybrid fish resulted from first-generation (F1) hybridization events, which occurred exclusively between silver kob females and dusky kob males. Whether hybridization is the result of natural events (such as secondary contact following a shift in distribution range), or anthropogenic activities (size-selective pressure due to overfishing), these findings have important implications for critical recovery and future management of these species in the wild.

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Section: Resultsmentioning

confidence: 99%

Section: Squaretailmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Identification of naturally occurring hybrids between two overexploited sciaenid species along the South African coast

Mirimin¹,

Kerwath²,

Macey³

et al. 2014

Molecular Phylogenetics and Evolution

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“…This is the case of meagre and other large-sized sciaenids, in which anatomical scales with four levels (Hermas 1995), five levels (Tixerant 1974), six levels (Abou Shabana et al 2012), seven levels (Griffiths 1996) and eight levels (Farmer 2008, Gil et al 2013) have been previously used in describing the male reproductive cycle. In such species, the few studies that used histology sections to assess reproductive parameters did not detail the histological results (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…The set included characteristics reported in previous meagre studies (Tixerant 1974) and in studies of other large sciaenids (Murphy and Taylor 1990, Griffiths 1996, Farmer 2003, and two characteristics that were found varying with fish size and/or season: a) the presence/absence of a groove running longitudinally along the proximal side of each testicle which makes this side appear concave (hereafter termed the proximal groove) and b) the presence/absence of striae, generally over two centimetres long, running longitudinally on the ventral surface of spent testicles (hereafter termed ventral striae). Objectively defined levels were set for each morphological feature with no a priori judgment of gonad maturity being made.…”

Section: Macroscopic Analysismentioning

confidence: 99%

Reproductive phase determination in male meagre (<em>Argyrosomus regius</em>, Sciaenidae): testis development and histologic corroboration of a gross anatomical scale

Prista¹,

Gordo²,

Costa³

et al. 2014

Sci. Mar.

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Summary:Reproductive stage determination of male gonads has received sparse attention in fish biology literature with few studies detailing the building of gross anatomical-and histologic scales. The meagre (Argyrosomus regius) is one of the world's largest sciaenids and supports a significant regional fishery in European and North African waters whose reproductive patterns are yet to be fully investigated. In the present study, we derive a macroscopic grading system for meagre testis using semi-quantitative graphs that feature the testis variability along the species size range and time of the year. We then describe the histological stages and reproductive phases of male testes and determine the extent to which they corroborate the anatomical scale. Our results indicate that gross anatomical analyses are accurate in assessments of the meagre spawning season but may not precisely distinguish the testes of well-mature fish and first spawning virgins. Furthermore, we show that milt expression varies widely with size and misclassifies as immature many smaller fish in spawning-capable condition. We discuss these findings in terms of their contribution to the understanding of testes development and the uncertainties involved in determining the size-at-maturity of male fish using gross anatomical scales.Keywords: histology; testes; reproduction; males; validation; Argyrosomus regius.Determinación de la fase reproductiva en los machos de la corvina (Argyrosomus regius, Sciaenidae): desarrollo de los testículos y corroboración de una escala anatómica Resumen: La determinación de la etapa reproductiva de las gónadas masculinas ha recibido escasa atención en la literatura con poca información disponible sobre la construcción de escalas macroscópicas e histológicas. La corvina (Argyrosomus regius) es uno de los más grandes esciaénidos mundiales y registra pesquerías regionales significativas en las aguas europeas y del norte de África pero sus patrones reproductivos han sido poco investigados. En el presente estudio, se deriva un sistema de clasificación macroscópica para los testículos de la corvina utilizando gráficos semi-cuantitativos que contemplan la variabilidad de los testículos respecto al tamaño de los ejemplares a lo largo del año. A continuación se describen las etapas histológicas y fases reproductivas de los machos y se corrobora la escala macroscópica. Nuestros resultados indican que los análisis macroscópicos son exactos en las evaluaciones de la estación de puesta pero pueden no ser capaces de distinguir con precisión los testículos de peces bien maduros y en la primera madurez. Además, se muestra que la expresión de esperma varía con el tamaño del pez lo que puede dar lugar a clasificar erróneamente como inmaduros peces jóvenes que se encuentran en condiciones de puesta. Estos resultados se discuten en términos de su contribución a la comprensión actual del desarrollo de los testículos y de las incertidumbres que rodean el uso habitual de las escalas macroscópicas en la valoración de la talla de madurez d...

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Quantitative SWOT analysis of key aquaculture species in South Africa

Babatunde

Deborah

Gan

et al. 2021

Aquaculture Fish & Fisheries

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South Africa produces both marine and freshwater aquaculture species, with a combined production output of 5418 tons of food fish in 2015. Key aquaculture species reportedly cultured include four marine species -abalone, dusky kob, mussels and oysters and seven freshwater species -tilapia, trout, catfish, marron crayfish, carp, koi-carp and ornamental species. The study aims to quantitatively assess the SWOT factors (Strengths, Weaknesses, Opportunities and Threats) of major aquaculture species of South Africa to determine their aquaculture development and market potential. Key food fish species -abalone, dusky kob, mussel, oyster, salmon, trout, tilapia, catfish and marron crayfish, were selected and subjected to qualitative and quantitative SWOT analyses by adapting the quantified SWOT analytical method coupled with the multi-attribute decision-making method MADM (SWOT-MADM). Trout and tilapia are positioned in quadrant I, showing a combination of competitive strengths and market opportunities. Abalone, oyster and marron crayfish are situated in quadrant II; thus, they possess market opportunities but weak in competitive strengths as aquaculture species. Salmon and dusky kob are positioned in quadrant III; both species are weak in competitive strengths and faced with more threat factors rather than market opportunities. Mussel and catfish are in quadrant IV; both species thus have competitive strengths but are facing more threats than opportunities. Catfish recorded the highest competitive strengths due to internal assessment factors such as low FCR, ability to tolerate very high stocking density, rapid growth rate, high survival rate, hardiness and versatility of production systems and locations. Abalone and marron crayfish, on the other hand, both exhibited more market opportunities compared to other key aquaculture species due to external assessment factors like high pricing and good financial indicators. The study is expected to add to the existing body of knowledge and in guiding aquaculture industry stakeholders to make informed decisions with regards to the feasibility of aquaculture species in South Africa.

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Life history of the dusky kobArgyrosomus japonicus(Sciaenidae) off the east coast of South Africa

Cited by 100 publications

References 15 publications

Identification of naturally occurring hybrids between two overexploited sciaenid species along the South African coast

Identification of naturally occurring hybrids between two overexploited sciaenid species along the South African coast

Reproductive phase determination in male meagre (<em>Argyrosomus regius</em>, Sciaenidae): testis development and histologic corroboration of a gross anatomical scale

Quantitative SWOT analysis of key aquaculture species in South Africa

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