Monogamy,spawning and skin-shedding of the sea moth,Eurypegasus draconis (Pisces: Pegasidae)

Synopsis The Red Sea seamoth, Eurypegasus draconis, has a social structure that involves close pair-bonding with a monogamous mating system. The occurrence of 61 specimens, 95.1% paired, were recorded in the Gulf of Aqaba, during summers 1989 and 1990. Fourteen pairs were tagged and seven of them were seen again at least once. Cumulative location maps for tagged individuals showed that they were not territorial or site-attached, home ranges of pairs overlapped, they had low mobility, and occurred in low densities. Dissections and histological analyses showed that pairs (n = 12) were heterosexual and all individuals were sexually mature. E. draconis is sexually dimorphic. Females (n = 13) have significantly larger carapace volumes than males (n = 13). In aquaria, pairs spawned repetitively at dusk. At the peak of a spawning rise they released pelagic eggs from which embryos hatched in 24–29h at 27.2°C. Unpaired individuals probably have little opportunity to meet and mate. Close pair-bonding that ensures the availability of a mate, probably evolved as a style for increasing reproductive success in these small fish that occur in low density. E. draconis sheds its skin in one piece every 1 to 5 days.     

Dragonflies (Insecta,Odonata) from the Red Sea Hills and the main Nile in Sudan

Twenty-one species of dragonflies are recorded from the Nile and the Red Sea Hills in the Sudan. The majority are species of africotropical origin, but wide-ranging and tolerant of strongly fluctuating environmental conditions. A small but significant fraction is restricted to the Nile Valley, and another fraction, found only in the Red Sea Hills, is composed of Eremian species of Palaearctic origin. Besides adults, the last-instar larvae of Pseudogrion niloticum and of Paragomphus pumilio are described and figured.     

Reproductive segregation among the Barbus intermedius complex of Lake Tana,Ethiopia. An example of intralacustrine speciation?

Reproductive segregation among the large barbs Barbus intermedius complex, Cyprinidae , of Lake Tana, Ethiopia, was investigated in the mouths and upstream reaches of rivers tributary to the lake, during the spawning seasons of 1993 and 1994. The percentage of running fish of four Barbus morphotypes [Acute (Ac), Bigmouth big-eye (Be), Intermedius (In), and Shorthead (Sh)] peaks with the highest water level of the lake. Large differences are apparent in the minimum fork length of running fish among morphotypes [c. 12 cm for male Sh and 28 cm for male Bigmouth small-eye (Se)]. Significant differences occur in temporal, but especially in spatial patterns of the relative abundance of running morphotypes, when the lake is compared with the four major river mouths and their upstream reaches. These different relative abundances are clearest among Ac, Be, In, Sh and Troutlike (Tr). Also, the absence from the rivers of some morphotypes that are usually abundant in the lake itself [Barbel (Ba), Dark (Da), Lip (Li), and Zurki (Zu)], and the abundant presence in the rivers of Tr, rare in the lake, strengthen the hypothesis that spatial and/or temporal spawning segregation is present among the morphotypes. There are indications that Bighead (Bh) and Zu spawn in the lake itself, while other morphotypes were only found running in or near rivers. Combined with the morphological, ecological, and genetic differences, these data suggest the existence of several Barbus species, forming a unique species flock, which probably evolved within the lake. The presence of several, instead of one Barbus species complicates management of sustainable fisheries and protection of the lake's biodiversity. Present results show the importance of the rivers for Barbus reproduction and stress the urgent need for careful management of fishing activities in spawning times and areas.     

Climate induced increases in species richness of marine fishes

Climate change has been predicted to lead to changes in local and regional species richness through species extinctions and latitudinal ranges shifts. Here, we show that species richness of fish in the North Sea, a group of ecological and socio-economical importance, has increased over a 22-year period and that this rise is related to higher water temperatures. Over eight times more fish species displayed increased distribution ranges in the North Sea (mainly small-sized species of southerly origin) compared with those whose range decreased (primarily large and northerly species). This increase in species richness can be explained from the fact that fish species richness in general decreases with latitude. This observation confirms that the interaction between large-scale biogeographical patterns and climate change may lead to increasing species richness at temperate latitudes.     

Biogeography of the family Acartiidae (Calanoida) in the Ponto-Mediterranean Province

In the Ponto-Mediterranean Province, the geographical distribution of 19 species plus 1 variety belonging to the family Acartiidae has been studied. The study utilised cartographic techniques of terrestrial biogeography and the entire Province was subdivided in 1375 squares. The geographic distributions obtained derived from data published during the last 126 years. The first result was that about 3/4 of the area considered has never been sampled, and only about 8% of the entire area has been repeatedly sampled (at least seasonally). Long time-series of sampling are known only from very few sites. The species considered belong to three genera. Species distributions are discontinuous either in space or in time. Three species are endemic. The historical analysis suggests that four species arrived in the Province recently (two of them are Lessepsian migrants; the others have been introduced by human activities). Two species appear to have crossed the Suez Canal from the Mediterranean to the Red Sea (anti-Lessepsian migration). Two species are considered to be ante-Lessepsian (they were tropical species present in the Mediterranean before the Suez Canal opening). The doubtful presence of two species in the Mediterranean is discussed. At the present time, it seems that the distribution of many species is rapidly changing, probably as a consequence of the anthropogenic influence on communication between areas of the Province, and supported by the ability of Acartiidae to cross geographic barriers, mainly as resting stages.     

Feeding and growth of the pearl oyster Pinctada margaritifera (L.) in Dongonab Bay,Red Sea

Plankton samples and gut contents of P. margaritifera were analysed monthly from April 1972 to March 1973. Coscinodiscus sp. was the most ingested food by pearl oysters of all ages. However, food variety increased as the oyster grew older. Experiments confirmed the absence of food selectivity in P. margaritifera. Unlike the young ones, the adult showed reduced growth during summer (July–September), which coincides with its spawning season.     

Revisiting the Freedom of Fishing and Legal Obligations on States Not Party to Regional Fisheries Management Organizations

For decades, states have cooperated through regional fisheries management organizations (RFMOs) on the conservation and management of living marine resources on the high seas. Nonmembers, or third states not bound by their decisions, have been an Achilles’ heel. In this article, the legal status of RFMO nonmembers and the freedom of fishing are examined. It is concluded that RFMO nonmembers have concrete obligations with respect to established fisheries subject to RFMO regulation.     

The reproductive and feeding biology of Schilbe intermedius Rüppell in the Okavango Delta,Botswana

The reproductive and feeding biology of 314 Schilbe intermedius Rüppell 1832 collected in the Okavango Delta, Botswana, between April 1985 and February 1986 during low, intermediate and high water level were investigated. S. intermedius matures at 130 mm standard length and is a monocyclic spawner. Females predominate in the population and have an average fecundity of 27107 eggs. In the northern riverine floodplain of the Delta fish spawn in mid-summer during the peak flood. In the southern drainage rivers fish spawn in spring, which is two to three months after the arrival of the winter flood waters. S. intermedius is an opportunistic predator with a diet consisting largely of fish 41%, aquatic larvae 25%, terrestrial insects 14%, aquatic insects 7% and crustacea 5%. Juvenile S. intermedius feed predominantly on insect larvae, while adults are largely piscivorous.