The South African demersal trawl fishery, as with most trawl-directed fisheries worldwide, has a substantial bycatch component. With increasing commercial emphasis being placed on retained bycatch, an urgent need has arisen to investigate these species. In the past the bycatch component has received little research or management attention. Members of the gurnard family Triglidae make up up to 2.4 % of the South African hake-directed demersal catch and are thus considered an important bycatch species. The catch history and biology, including population structure, reproduction, feeding, age, growth and mortality, of the Cape gurnard, Chelidonichthys capensis, sampled from the Agulhas Bank, South Africa, were thus investigated. Males (mean TL = 366mm) were significantly smaller than females (mean TL = 411mm). The sex ratio was close to parity, males being more dominant in commercial trawls and less dominant in research trawls. Gonad maturation and gonadosomatic indices showed this species to have an extended spawning period with peaks in reproductive activity during September, January and April. First approximations of size at 50 % maturity were similar for females (349mm TL) and males (348mm TL) but differed significantly in terms of age (3.6 years and 4.6 years respectively). Otolith growth marks were validated as annuli using marginal zone analysis. The maximum age estimated was 16 years for a female of 675mm TL and recruitment to the commercial fishery was estimated as taking place in the fifth year of growth for both males and females. Gut content analysis showed C. capensis to be an opportunistic feeder preying preferentially on the benthic crustaceans Goneplax angulata and Mursia cristimanus. Landings from the commercial linefishery were insignificant whilst those for the commercial trawl fishery ranged from 500 tonnes to 3250 tonnes between 1984 to 1995, and indicated that this species forms an important component of the South African trawl fishery bycatch. A first approximation of fishing mortality (0.36 year⁻¹) for the inshore commercial trawl fishery was higher than that of natural mortality (0.25 year⁻¹) suggesting some fishing pressure on this species on the Agulhas Bank. However this fishing mortality value was significantly less than that for F₀·₁ (4.78 year⁻¹) that was estimated using a yield-per-recruit model.

Submitted by Alberto Vieira (martins_vieira@ibest.com.br) on 2018-06-15T19:11:10Z No. of bitstreams: 1 273649.pdf: 5583224 bytes, checksum: d138ec8299de44bf151b48f96d02d99b (MD5) / Made available in DSpace on 2018-06-15T19:11:10Z (GMT). No. of bitstreams: 1 273649.pdf: 5583224 bytes, checksum: d138ec8299de44bf151b48f96d02d99b (MD5) Previous issue date: 1995-10 / A ordem Scorpaeniformes é muito diversificada morfologicamente e tem como único caráter definindo o grupo um processo suborbitário que consiste de uma extensão posterior do terceiro infra-orbital até o pré-opérculo. Esta ordem apresenta muitos problemas sistemáticos e relações filogenéticas pouco conhecidas. Foram analisadas citogeneticamente 4 espécies pertencentes a 3 famílias da ordem: Scorpaena brasiliensis, Scorpaena isthmensis (Scorpaenidae), Prionotus punctatus (Triglidae) e Dactylopterus volitans (Dactylopteridae ). Os exemplares estudados foram coletados no litoral do Estado do Rio de Janeiro, Brasil. Este estudo teve como objetivo contribuir com o conhecimento da citotaxonomia e filogenia da ordem. Os cromossomos mitóticos foram obtidos através de preparação direta ou de cultura de curto termo. Foram estabelecidos... / The order Scorpaeniformes is morphologically diverse and the only character defining the group is a bony suborbital stay extending posteriorly from the third infraorbital to the preopercle. This order shows a great number of systematic problems and the phylogenetic relationships within the group are not clear. Four species belonging to three families of the order Scorpaeniformes were cytogenetically analyzed: Scorpaena brasiliensis, Scorpaena isthmensis (Scorpaenidae ), Prionotus punctatus (Triglidae) and Dactylopterus volitans (Dactylopteridae). The specimens were collected in the coast of Rio de Janeiro, Brazil. This study has the aim of contributing to the knowledge of the cytotaxonomy and phylogeny of the order. Mitotic chromosomes were obtained from cellular suspensions, either through air-drying or short term culture techniques. Giemsa karyotypes were established...

Invasive species, such as the red lionfish, Pterois volitans, are damaging many ecosystems around the world by out-competing native species. However, little work has been done to determine if P. volitans have a direct influence on the feeding performance of native species with which they compete. This study examines the feeding performance in terms of suction pressure, kinematic timing, and excursion distances of spotted scorpionfish, Scorpaena plumieri. Through multiple trials it was examined how S. plumieri modulate their kinematic behavior in response to P. volitans and a conspecific. The creation of a smaller buccal cavity and a decrease in time of buccal expansion may allow individuals to create greater sub-ambient pressures to increase their prey-capture success. High-speed cinematography and pressure transducers were used to determine if S. plumieri modulate feeding performance in the presence of either P. volitans or a conspecific. The results of the study suggest that S. plumieri do not create larger subambient pressures or modulate their feeding kinematics in the presence of P. volitans or a conspecific.