JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. American Society of Ichthyologists and Herpetologists (ASIH)is collaborating with JSTOR to digitize, preserve and extend access to Copeia.In this study I review the literature on resource partitioning in fish assemblages from 1940-83. Studies are grouped into seven global habitats: tropical reefs, temperate reefs, coastal marine, the Antarctic, mesopelagic/slope environments and freshwater streams and lakes. Freshwater systems first attracted the interest of resource ecologists; however, the number of studies of assemblages in all global habitats has risen sharply in the last decade.Studies treating single fish families show that resource partitioning occurs along more resource axes in more diverse assemblages. Unlike terrestrial systems, trophic separation is more important than habitat separation in fish assemblages. Based on 37 studies which concurrently examined habitat, food and temporal axes, 32% showed primary separation by habitat, 57% showed the greatest separation by food and 11% showed temporal separation to be most important. Global habitat differences in the importance of major resource axes are difficult to determine because of sampling bias; however, fish assemblages in most habitats show approximately equal importance of separation along spatial and trophic dimensions. The exceptions are marine systems, especially tem-1(41)

Cytochemical and in vitro whole‐cell patch clamp techniques were used to investigate granule cell hyperexcitability in the dentate gyrus 1 week after fluid percussion head trauma. The percentage decrease in the number of hilar interneurones labelled with either GAD67 or parvalbumin mRNA probes following trauma was not different from the decrease in the total population of hilar cells, indicating no preferential survival of interneurones with respect to the non‐GABAergic hilar cells, i.e. the mossy cells. Dentate granule cells following trauma showed enhanced action potential discharges, and longer‐lasting depolarizations, in response to perforant path stimulation, in the presence of the GABAA receptor antagonist bicuculline. There was no post‐traumatic alteration in the perforant path‐evoked monosynaptic excitatory postsynaptic currents (EPSCs), or in the intrinsic properties of granule cells. However, after trauma, the monosynaptic EPSC was followed by late, polysynaptic EPSCs, which were not present in controls. The late EPSCs in granule cells from fluid percussion‐injured rats were not blocked by the NMDA receptor antagonist 2‐amino‐5‐phosphonovaleric acid (APV), but were eliminated by both the non‐NMDA glutamate receptor antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) and the AMPA receptor antagonist GYKI 53655. In addition, the late EPSCs were not present in low (0·5 mM) extracellular calcium, and they were also eliminated by the removal of the dentate hilus from the slice. Mossy hilar cells in the traumatic dentate gyrus responded with significantly enhanced, prolonged trains of action potential discharges to perforant path stimulation. These data indicate that surviving mossy cells play a crucial role in the hyperexcitable responses of the post‐traumatic dentate gyrus.

The Southeastern Fishes Council Technical Advisory Committee reviewed the diversity, distribution, and status of all native freshwater and diadromous fishes across 51 major drainage units of the southern United States. The southern United States supports more native fishes than any area of comparable size on the North American continent north of Mexico, but also has a high proportion of its fishes in need of conservation action. The review included 662 native freshwater and diadromous fishes and 24 marine fishes that are significant components of freshwater ecosystems. Of this total, 560 described, freshwater fish species are documented, and 49 undescribed species are included provisionally pending formal description. Described subspecies (86) are recognized within 43 species, 6 fishes have undescribed subspecies, and 9 others are recognized as complexes of undescribed taxa. Extinct, endangered, threatened, or vulnerable status is recognized for 28% (187 taxa) of southern freshwater and diadromous fishes. To date, 3 southern fishes are known to be extinct throughout their ranges, 2 are extirpated from the study region, and 2 others may be extinct. Of the extant southern fishes, 41 (6%) are regarded as endangered, 46 (7%) are regarded as threatened, and 101 (15%) are regarded as vulnerable. Five marine fishes that frequent fresh water are regarded as vulnerable. Our assessment represents a 75% increase in jeopardized southern fishes since 1989 and a 125% increase in 20 years. The trend for fishes in the southern United States is clear; jeopardized fishes are successively being moved from the vulnerable category to that of imminent threat of extinction.

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We studied trophic relationships of Florida pompano (Trachinotus carolinus), gulf kingfish (Menticirrhus littoralis), scaled sardine (Harengu/a jaguana~ striped anchovy (Anchoa hepsetus) and dusky anchovy (A. /yo/epis) during their spring residency in the Horn Island, Mississippi, surf zone. Harengu/a jaguana, A. /yo/epis and A. hepsetus were zooplanktivores, utilizing primarily calanoid copepods, mysids and various decapod larvae. Menticirrhus /ittoralis and T. caro/inus utilized benthic prey including Donax, Emerita and polychaetes; however, small pompano also fed on zooplankton. Menticirrhus littoralis, T. carolinus, H. jaguana and A. lyo/epis also showed distinct dietary changes with increasing fish size. Three species, A. lyolepis, H. jaguana and M. littoralis fed at least partially at night, while T. carolinus and A. hepsetus were primarily diurnal predators. Cluster analysis of size intervals of all species based on presence or absence of prey taxa formed groups consistent with taxonomic relationships, thus indicating considerable interspecific resource separation.