Добірка наукової літератури з теми "Sparidae"

ABSTRACTThe Eocene sparid fauna (Teleostei: Percoidei) from Monte Bolca, Italy and from the London Clay, U.K. is revised based on re-examination of the type material and phylogenetic analyses of primarily osteological data. Two phylogenetic analyses, one of the Eocene taxa and a combined analysis of fossil and extant taxa, were performed. The addition of fossils to the extant data greatly increased numbers of most parsimonious trees, destabilising and obscuring basal relationships within the Sparidae. Combination of the data from fossil and extant data also affected relationships among the fossil taxa, changing some from those recovered using fossil data alone and destabilising others. Successive approximations character weighting supported the inclusion of the Eocene taxa within a monophyletic Sparidae. The genus Sparnodus, as previously conceived, is paraphyletic and is partitioned to remove the paraphyly. Five monotypic genera are recognised, including three new genera, Abromasta, Ellaserrata and Pseudosparnodus. Inclusion of the fossils in the phylogenetic analysis implies a minimum age of origin for the Sparidae of 55 Ma with most Recent sparid fauna in place no later than the Miocene, and provides further evidence that the diversification of feeding strategies occurred early on in the evolutionary history of the group.

A preliminary ontogenetic series of common pandora (Pagellus erythrinus) larvae is presented showing that larvae of this species possess an occipital crest from 4 to 16 mm total length. Such a trait has been described as a diagnostic character of the larvae of another sparid fish, namely Pagrus pagrus, and has been erroneously considered as being absent in all other Sparidae species. This caused confusion and erratic identifications of the two species of larvae in Mediterranean ichthyoplankton investigations.

Abstract The present paper deals with results of the study of porgy fish (Sparidae) remains from the upper Miocene, lower and upper Pliocene, and the lower Pleistocene of Ukraine. Isolated molariform teeth were assigned to Pagrus cinctus, Pagrus sp., as well as to Sparidae? gen. et sp. indet. These findings expand our knowledge of the species composition of the Late Cenozoic fish assemblages of Southeastern Europe and force partially reconsider conclusions formulated earlier about their environment.

Sexuality in seabreams (Sparidae) is considered to be more complex than in any other family of fishes. Early work indicated five reproductive styles within the family: protandry, protogyny, simultaneous hermaphroditism, rudimentary hermaphroditism and gonochorism. More recently two reproductive styles have been suggested: sex change (protandry and protogyny) and secondary gonochorism (rudimentary hermaphrodites). The need for detailed descriptions of sex differentiation, gonad development and spawning behaviour in this family has been identified by a number of workers in this field. The aims of the present study were: i) to provide accurate, detailed descriptions and comparisons of gonadal development in representatives of each reproductive style, ii) to investigate their spawning strategies, and iii) to relate these findings to current theories on hermaphroditism and sex change in fishes. Four species were investigated. Slinger, Chrysoblephus puniceus, the only known protogynous hermaphrodite in Natal. Santer, Cheimerius nufar, described in the literature as a rudimentary hermaphrodite. Riverbream, Acanthopagrus berda suspected to be a protandrous hermaphrodite. Natal stump nose, Rhabdosargus sarba, reported elsewhere as a protandrous hermaphrodite. Detailed histological analysis showed that morphological and cytological development of all gonads proceeded initially in a female direction, irrespective of reproductive style, but that differentiating gonads of protandrous and protogynous hermaphrodites could easily be distinguished from one another. Early gonadal development was similar in R. sarba and A. berda with gonadal primordia differentiating into distinctly bisexual organs. In C. puniceus and C. nufar gonadal primordia differentiated into ovaries with reduced, inert male elements in the tunica albuginea. Sex differentiation occurred relatively late (100-150mm fork length) in all the species investigated. Few cells conforming to primordial germ cells (PGC's) described in other teleosts were identified. These cells only became evident after the appearance of gonial cells and their identity is questioned. Gonial cells appeared to develop within less-electron-dense cysts of cells. Gonial cells in presumptive male and female elements could not be distinguished from one another morphologically, suggesting the bipotentiality of these cells. All R. sarba and A. berda gonads pass through a predominantly male phase and all fish function first as males, indicating protandrous sex change in both species. All C. puniceus and C. nufar gonads develop initially into ovaries. Sex change thus occurs in both species and protogyny in C. puniceus is confirmed. In C. nufar, sex change may occur before or after sexual maturity and its reproductive style remains uncertain. Investigations into the spawning habits of A. berda have shown that this species spawns inside the Kosi estuary at night. Eggs are released during peak ebb tides. Spawning occurs in large aggregations and several to many males compete to spawn with individual females. This spawning strategy does not conform to predictions made from the size advantage model for protandrous species. Chrysoblephus puniceus appears to have preferential spawning sites on down-current outer reef margins. Spawning was not observed in this species, but changes in behaviour, social structure and colour during the spawning season suggest that it may have a mating system similar to several protogynous labrids and scarids, in which territories are temporary. Cheimerius nufar has a similar mating system. Temporary territories are established by large males during the spawning season, which extends from August to November. Mating is by pair-spawning and dominant territorial males obtain a disproportionate number of matings. 'Streaking' appears to represent an alternative mating strategy for males until they attain a sufficient size to establish and defend territories. The mating pattern of C. nufar suggests that it is either a gonochorist which does not conform to current theoretical predictions; or that it is a protogynous hermaphrodite incorrectly diagnosed as a rudimentary hermaphrodite; or that protogyny in the Sparidae is an ancestral condition and C. nufar is in the process of evolutionary change from a protogynous to a gonochoristic form (or visa versa).

This study focused on obtaining sound quantitative data on the reproductive biology, length and age compositions and growth of the snapper Pagrus auratus in the waters off Carnarvon at ca 25oS and Perth at ca 32oS on the west coast of Australia and at ca 34oS on the south coast of Western Australia. Sampling thus encompassed both sub-tropical and temperate waters and the geographical range within which this species is abundant in Western Australia. The resultant data were used to explore the ways in which the biological characteristics of P. auratus differ with latitude and thus water temperature. An intensive sampling regime for eggs and spawning individuals of P. auratus was conducted in Cockburn Sound, a large marine embayment in the Perth region at ca 32oS. The resultant data were used to elucidate where and when spawning occurs in this large marine embayment and to determine more precisely the factors that influence the timing of spawning. The implications of the results presented in this thesis for the management of P. auratus, a species that has been subjected to very heavy fishing pressure in recent years, are discussed. The time and duration of spawning of P. auratus in the subtropical waters of Carnarvon differed markedly from those recorded for this sparid in the temperate and cooler waters of the Perth and the south coast regions. Spawning at Carnarvon occurred predominantly in the five months between late autumn (May) and mid spring (September), whereas it took place mainly in the three months between mid spring (October) and early summer (December) in the Perth region. Spawning of P. auratus on the south coast occurred predominantly in October and November in 2003 and 2004 and scarcely at all in 2005. Gonadal recrudescence was thus initiated when water temperatures were close to their maximum but declining in Carnarvon, and close to their minima and rising in the Perth and south coast regions, respectively. The prevalence of fully mature and spawning females in all three regions was greatest in those months when water temperatures lay between 19 and 21oC. Collation of the data in this thesis and those provided in the literature for other populations showed that the spawning period was related to latitude, occurring far earlier in sub-tropical than temperate waters. The females and males attained maturity at a far smaller total length (L50) in the Carnarvon region, i.e. 378 and 353 mm, respectively, than in the Perth region, 585 and 566 mm, respectively, and also the south coast region, i.e. 600 and 586 mm. The trends exhibited by the age at maturity parallel those for length, with the A50s for the two sexes increasing from ca 4 years in Carnarvon to ca 5.6 years in the Perth region and nearly 7 years in the south coast region. The L50 and A50 at maturity thus both increased with increasing latitude. Marginal increment analysis demonstrated that, irrespective of the number of opaque zones in the otoliths of P. auratus, a single such opaque zone is laid down each year in these otoliths. Furthermore, the trends exhibited by the monthly marginal increments showed that the opaque zone is laid down predominantly in winter in the subtropical waters of Carnarvon, as opposed to mainly in spring in the temperate waters of the Perth and south coast regions. Thus, the timing of formation of the opaque zone in the otoliths of P. auratus along the Western Australian coast is not related to the trends exhibited by water temperature, but, in both the Carnvarvon and Perth regions, was coincident with the timing of spawning. The maximum total lengths recorded for females and males in the Carnarvon region, i.e. 864 and 840 mm, respectively, were considerably less than the corresponding values of 1051 and 1056 mm in the Perth region, and 1083 and 1099 mm in the south coast region. Growth in the Perth and south coast regions was greater than in Carnarvon, as is reflected in, for example, the respective lengths of 820, 720 and 610 mm for females at 10 years of age, as determined from the von Bertalanffy growth equations. The length and age compositions in the Carnarvon and south coast regions were essentially unimodal, whereas those in the Perth region were bimodal. However, the 'mode' in the length-frequency distribution for the south coast region was located well to the right of that in the Carnarvon region, reflecting relatively lower contributions by individuals of the age cohorts of 3 to 6 years. The marked bimodality in the length-frequency distribution for P. auratus in the Perth region was due to the presence of a group of mainly smaller individuals caught outside Cockburn Sound and another of mainly larger individuals that were caught in Cockburn Sound and which formed part of a spawning aggregation in that embayment. The proportion of fish > 10 years old in the Carnarvon region declined markedly between 2003 and the following two years, presumably reflecting the effect of heavy fishing pressure. This contributed to the decision by fisheries managers to reduced the TAC in those waters after 2003. Age-frequency data demonstrated that annual recruitment success in Cockburn Sound varied greatly, with the 1991, 1992 and 1996 year classes being particularly strong, and recognizing that the relative numbers of the first two year classes did decline progressively between 2002 and 2004. Annual recruitment was particularly variable in the south coast region, with the catches of the 1996 year class dominating the samples. The relative number of early stage P. auratus eggs in ichthyoplankton samples collected from Cockburn sound on each of four new moons during the spawning seasons of four consecutive years peaked in November in three of those years, i.e. 2001, 2003 and 2004, and in November/December in the remaining year, i.e. 2002. This showed that spawning in this embayment peaked during these months, at which times the mean sea surface temperatures ranged only from 19 to 20oC. The prevalence of spawning fraction females in sequential samples demonstrated that spawning peaks at the new and, to a lesser extent, full moons. This helps account for the strong positive correlation between spawning fraction and tidal regime, with spawning being greatest when the tidal range is greatest. Spawning times, back-calculated from the ages of the eggs collected during ichthyoplankton surveys in Cockburn Sound on each of 16 new moons within the spawning periods of four successive years, demonstrated that, in this embayment, P. auratus spawns at night and within the first three hours of the onset of the ebb tide. The distribution of egg concentrations on the 16 new moons showed that, each year, spawning occurred firstly in the north-eastern area of Cockburn Sound and then in the middle and finally north-western areas of this embayment. In the Perth region, the marine embayments of Cockburn and Warnbro Sound act as nursery areas for P. auratus during the first two years of life. The majority of 2 to 5 year old fish and a large proportion of the 6 year old fish occupy the marine waters outside the embayments. The remaining 6 year old and almost all of the older fish begin to move in September into particularly Cockburn Sound, where they form relatively large spawning aggregations between October and December, before undergoing a massive emigration from this embayment in December/January. The limited returns from fish that were tagged in Cockburn Sound and were subsequently caught outside this embayment indicate that, following spawning, P. auratus does not tend to move in a particular direction. Pagrus auratus stocks are heavily exploited in offshore, oceanic waters and in embayments, such as Cockburn Sound, where they are particularly susceptible to capture because of the tendency of this species to form spawning aggregations in these same easily accessible locations each year. The data obtained during this thesis show that the L50 at maturity of females and males in temperate waters, i.e. nearly 600 mm, is far greater than the current minimum legal length (MLL) of 410 mm TL. There is thus a need to increase the MLL and/or reduce fishing pressure on immature individuals in open waters. However, the effectiveness of an increase in the MLL may be limited because there is evidence that P. auratus suffers from fishing-induced barotrauma. Closures of specific areas during the spawning season of P. auratus, such as those that have been applied in Cockburn Sound and Shark Bay, are potentially a very effective method for reducing the effects of heavy fishing on spawning individuals.

The most significant bottleneck to the development of marine finfish culture is a reliable production of juveniles for growout. This is due to the small size at hatch and delicate nature of the pelagic larvae produced by most commercially desirable species. However, over the last 30 years, improved larviculture techniques have been developed to the extent that many species are being successfully cultured worldwide. These techniques were applied to two endemic species as a preliminary step towards establishing marine finfish aquaculture in South Africa. Adult roman Chtysoblephus laticeps and carpenter Argyrozona argyrozona (Pisces: Sparidae) were caught in the Tsitsikamma National Park. Both species responded to injection with pituitary extract, HCG and LHRHa, and were succesfully stripped up to 48 hours after injection. Fish were stripped twice, the second stripping producing better quality eggs. Chyrysoblephus laticeps also spawned naturally after injection with LHRHa. The fertilised eggs were incubated and the larvae reared in a fully recirculating seawater system. One batch of A. argyrozona and three batches of C. laticeps were reared through metamorphosis on a diet of enriched rotifers and Anemia, and inert foods, following commonly used rearing procedures. Both species followed developmental patterns of other cultured larvae, displaying typical critical stages; high mortalities at first-feeding and cannibalism from 26-30 days after hatch resulted in survival rates ranging from 0.1-0.5%. Growth, survival, size of gape at first-feeding, and ease of weaning onto an inert diet of C. laticeps was comparable to other species being reared for the first time, indicating some potential as a candidate species. The numbers of A. argyrozona larvae reared were insufficient to make comparisons with other studies. The adults also proved to be susceptible to physical damage while in captivity and were, therefore, considered unsuitable for aquaculture. The thesis describes the spawning procedure, the systems developed and the larval rearing process. The critical stages of first-feeding, swim bladder inflation, settlement and cannibalism are discussed and the development of the larvae described. The ontogeny of both species is described in detail. Both species displayed typical sparid developmental patterns, but differed with respect to pigmentation, head spination and morphometrics.

The blacktail, Diplodus sargus capensis and the zebra, Diplodus cervinus hottentotus, sparid fishes endemic to South Africa, are important components of the recreational shore-fishery. To provide a basis for the management of these fish, aspects of the biology of both species were investigated in the Tsitsikamma National Park (TNP). In particular, the role of the TNP was evaluated as a management option for the conservation of both species. Examination of stomach contents showed that juveniles of both species fed predominantly on amphipods, polychaetes and harpacticoid copepods. Adult !h. sargus were omnivorous and fed opportunistically on a wide variety of reef associated invertebrates and algae including echinoids, polychaetes, anthozoans, ascidians and rhodophytes. The diet of adult D. cervinus was more specialized with a preference shown for polychaetes and amphipods. Seasonal differences were apparent in the diets of both species where considerably more amphipods were consumed in winter than in summer. Feeding requirements of both species were reflected in their habitat preferences. Visual underwater assessment revealed that both species were most abundant on turbulent inshore reefs (1-10m). !h. sargus were observed over a wide variety of reef associated habitats. In the literature they have also been recorded in the surf zone of sandy beaches and in the lower reaches of estuaries. !h. cervinus, on the other hand, were more specific in their habitat requirements and were observed in greatest abundance on inshore reefs, often in close association with caves or overhangs. A comparison between the relative abundance and size structure of both species in the TNP with that of an exploited area immediately adjacent to the reserve, showed no significant differences. This was attributed to the low level of exploitation by rock-and-surf anglers occurring in the exploited study area, as well as the possibility of seeding of eggs and larvae, or emigration of adults from the TNP. An investigation of the reproductive biology of both fish showed that !h. sargus had an extended summer spawning season while in !h. cervi nus it was more restricted. Detailed histological examination of gonadal development showed that !h. sarqus were dygynous with partial protandry occuring in the male population. ~ cervinus were shown to be rudimentary hermaphrodites. Size at 50% maturity in ~ sargus and ~ cervinus was determined at 225 and 285mm fork length respectively, corresponding to ages of 4 and 6 years. An age and growth study based on the examination of sectioned otoliths showed that both species were slow growing capable of reaching ages in excess of 20 years. Growth in ~ sargus and ~ cervinus was described by the von Bertalanffy growth equations: L(t) = 309.44(1-e-0 . 247[t+l. 048 l) and L(t) = 396.85(1-e-0.146[t+2.148J) respectively. Life history characteristics of D. sargus and D. cervinus including slow growth, late maturation and occupation of a localised, demersal habitat showed that both species were vulnerable to the effects of over-fishing. Due to the present increase in the number of participants and the decrease in catch per unit effort in the recreational shore-fishery, more stringent management recommendations were proposed to ensure the adequate protection of both species. These included an increased minimum size limit and a decreased bag limit for both species. Based on the residency shown by both species and their high relative abundance in the TNP, marine reserves were considered to be a valuable addition to the suite of management options available for the conservation of these species . In this respect the reserve provided both protection for the spawner stock as well as the potential to seed adjacent areas.

Se ha llevado a cabo un estudio sobre el parasitismo branquial de 91 dentones (Dentex dentex, Pisces, Sparidae). Dicha muestra se compuso de 61 dentones salvajes capturados mediante palangre procedentes de aguas de Mallorca y canal de Menorca, y 30 dentones cautivos procedentes de una jaula situada en el puerto de Mallorca. Se encontraron un total de ocho especies parásitas, un dinoflagélido (Amyllodinium ocellatum), un monogénido (Microcotyle erythrini), un udonélido (Udonella caligorum), un trematodo digenea (Stephanostomum sp. metacercariae), tres copépodos (Caligus productus, Caligus diaphanus y Clavellotis fallax) y un isópodo (Gnathia vorax, praniza larvae). De dichas especies únicamente el dinoflagélido apareció en la muestra de peces cautivos, hallándose el resto de parásitos encontrados en la muestra de peces salvajes. El udonélido Udonella caligorum fue hallado como hiperparásito o foronte de los tres copépodos. Se describen, las prevalencias, intensidades y abundancias medias, así como otros parámetros ecológicos, igualmente se estudia la distribución espacial de cada parásito sobre el tejido branquial. Se discute el hipotético daño que las infecciones producidas por estos parásitos podrían causar en peces cultivados en el área de estudio. No se han podido establecer correlaciones positivas entre los diferentes parásitos y las condiciones de peso/talla del hospedador, no pudiendo concluir por lo tanto, que el número de parásitos aumente según lo hace el tamaño del hospedador. Sólo aparecieron correlaciones positivas entre los cáligos y C. diaphanus y C. fallax. Al ordenar los hospedadores por grupos de peso y estudiar las prevalencias, intensidades y abundancias medias de cada parásito, no se ha encontrado un patrón de comportamiento constante de los diferentes parásitos a lo largo de los grupos de peso. También se estudia qué ocurre con el parasitismo según la talla de los hospedadores, pues es este factor el que muestra la edad del animal. No se observaron diferencias de peso significativas en los hospedadores atribuibles a la carga de parásitos soportada. Por último se examinan cómo se asocian los diferentes parásitos en combinaciones multiparásitas.
A preliminary study of the gill parasites from 91 common dentex (Dentex dentex, Pisces, Sparidae) was developed. Sample was formed by 61 wild fishes caught in waters of Mallorca and Menorca channel (Balearic Islands) and 30 farmed fishes from a cage located in the harbour of Mallorca. Eight parasite species were found: one dinoflagellate (Amyllodinium ocellatum), one monogenean (Microcotyle erythrini), one udonellidean (Udonella caligorum), one digenean trematode (Stephanostomum sp. metacercariae), three copepods (Caligus productus, Caligus diaphanus and Clavellotis fallax) and one isopod (Gnathia vorax, praniza larvae). The udonellidean U. caligorum was found as a hyperparasite or phoront of the three copepods. Prevalence, mean intensity and abundance and other ecological parameters as well as the spatial site of each parasite in the gill tissue are described. It also discusses the hypothetical damage that infections might cause in sea cage-farmed common dentex from the same area through interaction between wild and farmed common dentex populations. Positive correlations among the different parasites and the host conditions (size/weight) have not been found, so we could not affirm that the number of parasites increases with host body size. We only found positive correlations between both caligid copepods and between C. diaphanus and C. fallax. After grouping hosts in weight classes and studying the prevalence, mean intensity and abundance of each parasite, any of them showed a constant behavior pattern along such weight classes. Host size and parasitism is analyzed in order to know the possible relationship between parasitism and host age. No significative differences on host weight in relation with the parasitic burden were detected. The multiparasitic combinations are also examined.

Due to the nature of the marine environment genetic studies allow insight into behaviour and natural history that is difficult or impossible to identify by direct field observation. Current as well as historical population demography and gene flow can be detected by using molecular techniques. Genetic studies on only a few commercially important marine species along the South African coast have been conducted, although many marine fish species utilize estuaries as nursery areas and little attention has been afforded to studying larval distribution and recruitment of these species from a molecular point of view. Many of these estuarine associated species, especially in the South African milieu, are important for recreational and subsistence use. Associated with southern African estuaries are 13 species of the family Sparidae of which Cape stumpnose Rhabdosargus holubi is the most abundant. Juveniles are mostly confined to estuaries while the adults are strictly marine. Rhabdosargus holubi are serial spawners but temporally separated spawning peaks have been recorded along the South African coastline. Within the first part of this dissertation, the general characteristics of marine fish populations and the marine environment along the South African coast are being discussed. The main aim of this study was to determine the population genetic structure from estimates of nuclear and mitochondrial genetic variation across the distributional range of Rhabdosargus holubi. Samples were collected from 13 geographic localities along the South African coastline from St Lucia in the northeast to Klein River in the southwest. Juveniles were sampled in estuaries and adults were collected in the marine intertidal zone. Mitochondrial DNA control region fragments of 368 bp in length were obtained from a total of 214 individuals from all sampling localities. A total of 36 alleles were identified from 34 polymorphic sites. Following an allele homogeneity test, samples from different localities were lumped to represent six distinct geographical regions. Mitochondrial DNA control region analyses of juveniles showed high haplotype diversity and low nucleotide diversity with no divergent maternal lineages. No pattern between haplotype genealogy and geographic locality was evident. Population genetic analyses using heterologous microsatellite amplification have been successfully completed for a number of studies, including numerous studies of variation within marine fish species. Microsatellite studies have proven to be more sensitive in detecting subtle population structure than mtDNA and/or protein polymorphisms in high gene flow species. A total of 113 microsatellite loci previously isolated from phylogenetically closely related marine fish species were tested for amplification. The success rate of heterologous microsatellite amplification was extremely low (0.02%), with only two polymorphic loci amplifying consistently for analysing 133 individuals sampled from six localities along the distributional range of R. holubi. Results from these two loci were insufficient to draw conclusions about the population genetic structure of R. holubi along the South African coast. Possible reasons for the low rate of amplification success and future research recommendations are discussed. The findings from this study suggest that R. holubi is not geographically restricted, has high gene flow among localities and likely exist as a single stock.
Dissertation (MSc (Genetics))--University of Pretoria, 2006.
Genetics
unrestricted

The Scotsman Seabream, Polysteganus praeorbitalis, is one of several large, slow-growing members of the Sparidae family of fishes endemic to the Agulhas Current system in the Western Indian Ocean (WIO). Relatively little research has been conducted on this species despite its importance to both recreational and commercial line fisheries in South Africa and the drastic decline in catch per unit effort (CPUE) that has been recorded since the 1940s. Changing sea temperatures as a result of global climate change are further expected to affect the distribution and abundance of many fish species based on their thermal tolerances, life histories and population structures. The ability of these species to shift their distribution and adapt to new environments and thermal conditions will depend to some degree on the levels of genetic variation and gene flow, within and between populations. A combined approach using species distribution modelling and genetic analyses may prove to be a useful tool in investigating the potential effects of climate change on the distribution and genetic diversity of species. An ensemble species distribution model (SDM) based on 205 occurrence records and 30 years of Reynolds Optimum Interpolated (OI) sea surface temperature data was constructed to predict the distributional response of P. praeorbitalis to climate change in the Agulhas Current system. The ensemble SDM displayed a true skill statistic (TSS) of 0.975 and an area under the receiver operating curve (ROC) of 0.999, indicating good model fit. Autumn and winter minimum temperatures, as well as bathymetry, were the most important predictor variables in the majority of models, indicating that these variables may directly constrain the distribution of P. praeorbitalis. In particular, the southern range edge of this species appeared to be constrained by autumn and winter minima, with high model agreement on this range edge. Conversely, the northern range limit showed poor model agreement leading to a gradual reduction in occurrence. This indicates that this range edge may be constrained by other factors not included in the models such as species interactions. The ensemble SDM projected the current range of P. praeorbitalis to be 1500 km², smaller than the published range for this species. The model underestimated the northern range edge of this species by approximately 5° latitude when binary transformed. This is probably due to the rarity of this species in the landings of the Mozambican linefishery, which was assumed to be an indication of low abundance of P. praeorbitalis in these waters. The absence of a specimen to verify the published northern range edge of this species indicates that the northern range edge produced by this model is likely to be closer to the actual range limit of the species. A range contraction of 30% occurring at both the northern and southern edge of P. praeorbitalis’ range and range fragmentation occurring, towards its northern range edge by 2030, was predicted. These changes are modelled to be the results of cooling related to the intensification of the Port Alfred upwelling cell and of warming predicted north of the Natal Bight and in southern Mozambique. Genetic analyses of the nuclear DNA (nDNA) S7 intron 1 and mitochondrial DNA (mtDNA) control region genes were carried out using 118 tissue samples of P. praeorbitalis collected at four main localities: the Eastern Cape, Transkei, southern KwaZulu-Natal and northern KwaZulu-Natal. Analyses of genetic diversity levels revealed relatively low diversity in the mtDNA dataset (Hd = 0.488; π = 0.004) and moderate levels of diversity in the nDNA dataset (Ad = 0.922; π = 0.005). The low levels of diversity observed in the mtDNA dataset might be explained by a number of factors, including high variation in spawning success, the negative effects of over-harvesting, or a recent population bottleneck. The last explanation is supported by characteristic star-shaped haplotype networks and unimodal mismatch distributions displayed by both datasets. These results, in conjunction with a significant (p = 0.005) negative Tajimas D value (-2.029) in the mtDNA dataset and significant (p = 0.0005) negative Fu’s F statistic in both the nDNA (F = -26.5) and mtDNA (F = -11.9) datasets, provide strong evidence for a recent population expansion after a bottleneck event in this species. Spatially, mtDNA diversity was highest in the Eastern Cape and lowest in the middle localities, while nDNA diversity showed the opposite pattern. These results may be indicative of differences in the sex ratio between localities, possibly as a result of the protogynous hermaphroditism that has been postulated for this species. Although pairwise comparisons and exact tests of population differentiation revealed no significant geneticdifferentiation between populations in the mtDNA dataset, there was some evidence of low levels of differentiation in the nDNA dataset. This occurred for comparisons between the Eastern Cape and Transkei (Fst = 0.039; p <0.05), and the northern KwaZulu-Natal (Fst = 0.045; p < 0.05).. This might be the result of one or a combination of factors including the effects of the Port Alfred upwelling cell on dispersal and gene flow, or the possibility of more than one spawning ground for this species promoting sub-structuring. A SAMOVA analyses run on the nDNA dataset maximised variance by grouping the Eastern Cape and southern KwaZulu-Natal together and Transkei and northern KwaZulu-Natal together in two groups. This revealed no evidence of spatial structure (p = 0.36), with only 3.30% of variation explained by this grouping. The removal of individuals below the estimated length at 50% maturity in the nDNA dataset, in order to test for temporal structure, resulted in stronger evidence of differentiation between the Eastern Cape and all other localities: Transkei (Fst = 0.081; p< 0.05), southern KwaZulu-Natal (Fst = 0.031; p<0.05), and northern KwaZulu-Natal (Fst = 0.078; p< 0.05). This indicates that some temporal genetic structure may exist between age classes within this species. The differentiation observed between the Eastern Cape and other localities, coupled with the high percentage of private haplotypes in the mtDNA dataset in this locality, indicates that this area is where P. praeorbitalis is most vulnerable to the potential negative effects of climate change on its genetic diversity. However, the vast majority of this species genetic diversity appears to reside towards the centre of its range where it is most abundant and the lack of strong genetic structure indicates high levels of gene flow. In conclusion, while P. praeorbitalis is vulnerable to range loss as a result of climate change, its genetic diversity is unlikely to be greatly affected.