Many studies have recently described and interpreted the community structure and function of fishes inhabiting estuaries and other transitional waters in terms of categories or guilds. The latter describe the main features of the fishes’ biology and the way in which they use an estuary. However, the approach has been developed by different workers in different geographical areas and with differing emphasis such that there is now a need to review the guilds proposed and used worldwide. The previous wide use of the guild approach has involved increasing overlap and/or confusion between different studies, which therefore increases the need for standardization while at the same time providing the opportunity to reconsider the types and their use worldwide. Against a conceptual model of the importance of the main features of fish use in estuaries and other transitional waters, this review further develops the guild approach to community classification of fish communities inhabiting those areas. The approach increases the understanding of the use of estuaries by fishes, their interactions and connectivity with adjacent areas (the open sea, coastal zone and freshwater catchments) and the estuarine resources required by fishes. This paper gives a global perspective on this categorization by presenting new or refined definitions for the categories, lists the synonyms from the literature and illustrates the concepts using examples from geographical areas covering north and central America, north and southern Europe, central and southern Africa, Australia and the Indo‐Pacific.

each containing multiple guilds. Emphasis has been placed on ensuring that the terminology and 31 definitions of the guilds follow a consistent pattern, on highlighting the characteristics that identify the 32 different guilds belonging to the estuarine category and in clarifying issues related to amphidromy. As 33 the widely-employed term 'estuarine dependent' has frequently been imprecisely used, the proposal 34 that the species found in estuaries can be regarded as either obligate or facultative users of these 35 systems is supported and considered in the guild context. Thus, for example, species in the five guilds 36 comprising the diadromous category and those in the guilds containing species or populations 37 confined to estuaries are obligate users, whereas those in the marine and freshwater estuarine-38 opportunistic guilds are facultative users. 39 40

GDP-L-fucose is the activated nucleotide sugar form of L-fucose, which is a constituent of many structural polysaccharides and glycoproteins in various organisms. The de novo synthesis of GDP-L-fucose from GDP-D-mannose encompasses three catalytic steps, a 4,6-dehydration, a 3,5-epimerization, and a 4-reduction. The mur1 mutant of Arabidopsis is deficient in L-fucose in the shoot and is rescued by growth in the presence of exogenously supplied L-fucose. Biochemical assays of the de novo pathway for the synthesis of GDP-L-fucose indicated that mur1 was blocked in the first nucleotide sugar interconversion step, a GDP-Dmannose-4,6-dehydratase. An expressed sequence tag was identified that showed significant sequence similarity to proposed bacterial GDP-D-mannose-4,6-dehydratases and was tightly linked to the mur1 locus. A full-length clone was isolated from a cDNA library, and its coding region was expressed in Escherichia coli. The recombinant protein exhibited GDP-D-mannose-4,6-dehydratase activity in vitro and was able to complement mur1 extracts in vitro to complete the pathway for the synthesis of GDP-L-fucose. All seven mur1 alleles investigated showed single point mutations in the coding region for the 4,6-dehydratase, confirming that it represents the MUR1 gene.L-Fucose (6-deoxy-L-galactose) is a monosaccharide found in a diverse array of organisms. The sugar is a known component of bacterial lipopolysaccharides, mammalian and plant glycoproteins, and polysaccharides of plant cell walls such as xyloglucan and rhamnogalacturonans I and II. The precise function of L-fucose within these polysaccharides is not clear, but it may stabilize conformations of xyloglucan, which can efficiently bind to cellulose microfibrils (1), possibly aiding in cell wall integrity. Furthermore, xyloglucan fucosylation is essential for the biological activity of some xyloglucan-derived oligosaccharides (2). The pathway for the synthesis of L-fucose has been studied biochemically, but genes for the corresponding enzymes have not been cloned from any eukaryote.GDP-L-fucose (guanosine-diphospho-L-fucose) is the activated form of this sugar, synthesized de novo from GDP-Dmannose via a three-step mechanism or through a salvage pathway involving phosphorylation of free L-fucose and subsequent nucleoside-diphosphate attachment (3-5). The de novo pathway for GDP-L-fucose production is shown in Fig. 1. The first step is catalyzed by GDP-D-mannose-4,6-dehydratase and involves the formation of the intermediate GDP-4-keto-6-deoxy-D-mannose, which is then used in the second and third steps of the pathway by 3,5-epimerase and 4-reductase activities to yield GDP-L-fucose. The pathway was initially elucidated in bacteria but has since been characterized in mammalian and plant systems (6)(7)(8)(9)(10)(11).Recently an L-fucose-deficient cell wall mutant, mur1, was isolated from Arabidopsis thaliana and characterized phenotypically (12). Eight recessive mur1 alleles were obtained from this screen, most of which exhibit 50-to 200-fold reducti...

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Data on the species compositions and the ages, sizes, reproductive biology, habitats and diets of the main species in the ichthyofaunas of seven estuaries in temperate southwestern Australia have been collated. Twenty‐two species spawn in these estuaries, of which 21 complete their lifecycles in the estuary. The latter group, which includes several species of atherinids and gobies with short lifecycles, make far greater contributions to the total numbers of fish in the shallows of these estuaries than in those of holarctic estuaries, such as the Severn Estuary in the United Kingdom. This is presumably related in part to far less extreme tidal water movements and the maintenance of relatively high salinities during the dry summers, and thus to more favourable conditions for spawning and larval development. However, since estuaries in southwestern Australia have tended to become closed for periods, there would presumably also have been selection pressures in favour of any members of marine species that were able to spawn in an estuary when that estuary became landlocked. Furthermore, the deep saline waters, under the marked haloclines that form in certain regions during heavy freshwater discharge in winter, act as refugia for certain estuarine species. The contributions of estuarine‐spawning species to total fish numbers in the shallows varied markedly from 33 or 34% in two permanently open estuaries to ≥ 95% in an intermittently open estuary, a seasonally closed estuary and a permanently open estuary on the south coast, in which recruitment of the 0 + age class of marine species was poor. The larger estuarine species can live for several years and reach total lengths of ~ 700 mm and some estuarine species move out into deeper waters as they increase in size. Several marine species use southwestern Australian estuaries as nursery areas for protracted periods. However, sudden, marked increases in freshwater discharge in winter and resultant precipitous declines in salinity in the shallows, and in other regions where haloclines are not formed, are frequently accompanied by rapid and pronounced changes in ichthyofaunal composition, partly due to the emigration of certain marine species. In contrast, the ichthyofaunal compositions of macrotidal holarctic estuaries undergo annual, cyclical changes, due largely to the sequential entry of the juveniles of different marine species for short periods. The ichthyofaunal compositions of the narrow entrance channels, wide basins and saline riverine reaches of large, permanently open southwestern Australian estuaries vary, reflecting the marked tendency for some species to be restricted mainly to one or two of these regions. Comparative data indicate that the characteristics determined for ichthyofaunas in southwestern Australian estuaries apply in general to estuaries elsewhere in temperate Australia.

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Extensive sampling of the intake screens of power stations in the Severn Estuary (Berkeley, Oldbury-upon-Severn and Uskmouth) and Bristol Channel (Hinkley Point) yielded a total of 97 species of lampreys, elasmobranchs and teleosts. Data were most comprehensive for Oldbury in the inner estuary where samples of all the fish collected over 24 h were obtained on four occasions in each month between July 1972 and June 1977. The Gadidae was the most abundant family at Oldbury, both in terms of numbers of individuals (51934) and species (13). The fifteen most abundant species at Oldbury included two anadromous (river lamprey (Lampetrafluviatilis), twaite shad (Alosafallax)), one catadromous (European eel (Anguilla anguilla)), one estuarine (common goby {Pomatoschistus microps)) and one freshwater species (3-spined stickleback (Gasterosteus aculeatus)). The remaining ten species, which fall within the broad category of estuarine-dependent marine species, contained a large proportion of o + individuals. This group comprised a species complex consisting of two morphologically very similar sand gobies {Pomatoschistus minutus and Pomatoschistus lozanoi), which were only separated during one year of the study, and the whiting (Merlangius merlangus), flounder (Platichthys flesus), bass (Dicentrarchus labrax), sea snail (Liparis liparis), poor cod (Trisopterus minutus), thin-lipped grey mullet {Liza ramada), herring (Clupea harengus), sprat (Sprattus sprattus) and bib (Trisopterus luscus). Juveniles of the last nine species took on average between 11-15 and 38-42 weeks to enter the shallows in the middle of the inner estuary from their spawning grounds, often having previously passed further up the estuary as postlarvae. These species showed a markedly seasonal pattern of occurrence at Oldbury, with the majority of each usually being collected within distinct two month periods. The number of species, and to an even greater extent the total number of fish, underwent consistent seasonal trends, with maximum and minimum values for the latter occurring between September and January and between March and May respectively. The seasonal trends for species richness (D), Shannon-Wiener (//') and Evenness indices (J) were similar, with maximum and minimum values generally occurring in the winter and summer respectively. A comparison between our data and those of earlier workers indicates that no major change has occurred in the composition of the fish fauna of the Severn Estuary during this century, except for the establishment of two 'northern' species, northern rockling (Ciliata septentrionalis) and Norway pout {Trisopterus esmarkii), during recent times.