A virtually intact subtropical reef community (14 phyla, 40 families and 62 non-native taxa) was associated with a rig under tow from Brazil that became stranded on the remote island of Tristan daCunha. This exposes rigs as a significant vector spreading alien marine organisms, and includes the first records of free-swimming marine finfish populations becoming established after unintentional movement. With relatively trivial effort, a pre-tow clean would have obviated the need to salvage and dispose of the rig (undertaken largely to address concerns about invasive species), at a cost of *US$20 million. Our findings show that towing biofouled structures across biogeographic boundaries present unexcelled opportunities for invasion to a wide diversity of marine species. Better control and management of this vector is required urgently. Simultaneous, unintentional introductions of viable populations of multiple marine organisms are rare events, and we develop a basic framework for rapid assessment of invasion risks.

In late 2006, diseased fish of a variety of species began to appear in the Chobe and upper Zambezi rivers in southern Africa. In April 2007, investigations showed that the levels of pesticides and heavy metals in the tissues of the fish were very low, discounting pollution as an underlying cause for the disease. However, histological evidence showed that the disease closely resembled the epizootic ulcerative syndrome caused by the oomycete Aphanomyces invadans, a serious aquatic pathogen that has been isolated from freshwater and estuarine fish in Japan, south-east Asia, Australia and the usa since the 1970s, but not previously recorded in Africa.

Age and growth in the scorpaenid Sebastes capensis was studied at Tristan da Cunha and Gough Island using otoliths. The growth rate of specimens collected at Gough Island was almost twice that of specimens collected at Tristan da Cunha. The largest specimen from Tristan was aged at 18 years while similar‐sized fish from Gough were only 11 years old. Because the populations at the two localities were not considered to be genetically isolated from one another, it was hypothesized that the difference in the growth rate and longevity was related to site‐specific environmental conditions. Inshore sea temperatures were, on average. 3°C higher at Tristan than at Gough throughout the year. It is concluded that this temperature difference may affect growth rate indirectly through regulating diet and metabolic activity in S. capensis. Changes in reproductive strategy related to the level of environmental predictability at the two localities may also affect growth rate in this species.

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The reproductive and recruitment characteristics of moggel, Labeo umbratus, populations were examined in four small South African reservoirs. Reproduction, characterised by an extended spawning season, high fecundity, short incubation time and rapid larval development, appears to be ideally suited to the highly variable environment of small reservoirs. Evidence suggested that L. umbratus spawns in the reservoirs. In two reservoirs where samples were conducted monthly, GSI (gonado-somatic index) was positively correlated with both water temperature and day length, whilst the CPUE (catch per unit effort) of juveniles was not related to any environmental variable. The success of moggel spawning appeared to increase when there was early spring and consistent summer rainfall.

SynopsisThe reproductive biology of the concha wrasse, Nelabrichthys ornatus, at Tristan da Cunha in the South Atlantic Ocean is described . Histological evidence shows that the species is a monandric protogynous hermaphrodite . N. ornatus displays full permanent sexual dichromatism with all males occurring in the upper size classes of the population . Size specific habitat preference is described . Aspects of the mating system of the species resemble a lek although the possibility of mating site selection by females is not discounted . Spawning groups have a sex ratio of between 4 and 7 females per male .