Marine Biology » Fish

Decline of endangered California delta smelt linked to nutrient pollution

_T14b — Mon, 14 Jun 2010 16:02:33 +0000

A new study recommends that efforts to restore the endangered California delta smelt and other declining pelagic fish should more sharply focus on reducing nutrient pollution to the species' native waters. The research indicates these fish populations would greatly benefit from reductions in the amount of nitrogen flowing into the Sacramento-San Joaquin Bay-Delta from waste-water treatment plants and balancing the ratio of nitrogen and phosphorus contained in the discharged water.... ...
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Prehistoric fish extinction paved the way for modern vertebrates; Event of unknown origin occurred as first vertebrates tested land

_T14b — Mon, 14 Jun 2010 16:02:32 +0000

A mass extinction of fish 360 million years ago hit the reset button on Earth's life, setting the stage for modern vertebrate biodiversity, a new study reports. The mass extinction scrambled the species pool near the time at which the first vertebrates crawled from water towards land, scientists report. Those few species that survived the bottleneck were the evolutionary starting point for all vertebrates -- including humans -- that exist today.... ...
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Oil spill threatens toothy marine predator that is cultural and historic icon

_T14b — Mon, 14 Jun 2010 16:02:28 +0000

The BP oil blowout in the Gulf of Mexico threatens the existence of a critically endangered sawfish and its relative that recently has been proposed to join it as the only two marine fish in United States waters to receive such federal protection.... ...
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New methodology to define safe distances between sensitive ecosystems and marine farms

_T14b — Mon, 14 Jun 2010 16:02:28 +0000

Scientists have developed a methodology to detect the influence of discharges from open water fish farms on marine ecosystems. With this methodology, based on the analysis of the isotopic signal of nitrogen in the tissue of marine macrophytes, coastal managers can select areas which are suitable for aquaculture under ecological criteria, in order to establish a safe distance between the farm and the sensitive ecosystem.... ...
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Could climate change and biodiversity of marine plankton in North Atlantic affect carbon cycle?

_T14b — Mon, 14 Jun 2010 16:02:27 +0000

Over the last decades, global warming has been accompanied by an increase in the taxonomic biodiversity of phytoplankton and zooplankton in the North Atlantic Ocean and a reduction in the average size of these organisms, according to researchers. They demonstrate that this structural modification of biological systems could bring about an alteration to the carbon sink in the North Atlantic and a reduction in the presence of subarctic fish such as cod.... ...
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Gamma-aminobutyric acid is a neurotransmitter in the auditory pathway of oyster toadfish, Opsanus tau

_T14b — Sun, 13 Jun 2010 05:01:02 +0000

Binaural computations involving the convergence of excitatory and inhibitory inputs have been proposed to explain directional sharpening and frequency tuning documented in the brainstem of a teleost fish, the oyster toadfish (Opsanus tau). To assess the presence of inhibitory neurons in the ascending auditory circuit, we used a monoclonal antibody to GABA to evaluate immunoreactivity at three levels of the circuit: the first order descending octaval nucleus (DON), the secondary octaval population (dorsal division), and the midbrain torus semicircularis. We observed a subset of immunoreactive (IR) cells and puncta distributed throughout the neuropil at all three locations. To assess whether contralateral inhibition is present, fluorescent dextran crystals were inserted into dorsal DON to fill contralateral, commissural inputs retrogradely prior to GABA immunohistochemistry. GABA-IR somata and puncta co-occurred with retrogradely filled, GABA-negative auditory projection cells. GABA-IR projection cells were more common in the dorsolateral DON than in the dorsomedial DON, but GABA-IR puncta were common in both dorsolateral and dorsomedial divisions. Our findings demonstrate that GABA is present in the ascending auditory circuit in the brainstem of the toadfish, indicating that GABA-mediated inhibition participates in shaping auditory response characteristics in a teleost fish as in other vertebrates. (C) 2010 Elsevier B.V. All rights reserved. ... ...
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The Effects of Grazing by Parrotfishes (Family Scaridae) on Selected Shallow Hawaiian Marine Communities

T11 — Sat, 12 Jun 2010 16:02:38 +0000

Title: The Effects of Grazing by Parrotfishes (Family Scaridae) on Selected Shallow Hawaiian Marine Communities Author(s): Brock, Richard Eugene Abstract: This study has been conducted to: (1) assess the quantitative effects that rasping parrotfishes in a coral reef ecosystem have on the structure of benthic communities; (2) describe the standing crop of parrotfishes and (3) examine scarid recolonization patterns on a fish depopulated patch reef. Field studies were conducted at both Johnston Atoll and Kaneohe Bay, Oahu, Hawaii from 1975 through 1977. These studies suggest that there are two principal groups of Hawaiian parrotfishes. i.e., those with heavy dentition (Scarus perspicillatus, S. sordidus and S. taeniurus) that consume large quantities of calcium carbonate and probably utilize endolithic resources and those possessing relatively lightweight dentition (Scarus dubius and Calotomus sandvicensis) that appear to feed primarily on epilithic organisms. The latter species are not particularly abundant possibly due to competitive interactions with other herbivorous fishes (e. g., acanthurids) on Hawaiian reefs. Using an acid dissolution technique of extraction, the cryptobiota are estimated to range from 10 to 1400 g/m2 (dry weight) and average about 50 g/m2 in most Hawaiian reef systems. This potentially large food resource is systematically harvested by few other large reef species besides some parrotfishes and sea urchins. Laboratory experiments conducted at the Hawaii Institute of Marine Biology in Kaneohe Bay using a flow-through seawater system suggests that parrotfish (Scarus taeniurus) at low density cause benthic community structure to proceed to macroalgal dominance. At intermediate density, (0.6 to 1. 5 parrotfish/m2 or 9 to 17 g wet weight/m2 ) a diverse, high biomass community (to 400 g/m2 dry weight) develops which may be enhanced by the presence of refuges. At Scarus densities greater than 1. 9 fish (20 g wet weight per m2 ) and in the absence of refuges, a benthic community of low diversity and biomass (3 to 8 g/m2, dry weight) develops. Under high grazing pressure coralline algae are competitively superior as manifested through greater coverage. Recruitment and growth of corals in the experimental situation correlates positively with increased grazing pressure and the presence of refuges (P < 0.01). These data suggest that parrotfishes may be important to the maintenance of the overall structure of coral reefs. thus acting as keystone species to other components of the benthic community. Parrotfish densities for optimum benthic community development in the laboratory are similar to those observed in some field situations (Kaneohe Bay, Oahu--1.1 fish or 10.8 g/m2 ), and maximal growth of juveniles occurs at such densities. Field experiments conducted at Johnston Atoll suggests that at normal field densities, parrotfishes may appreciably alter the benthic community structure in two dimensional (planar) systems. The addition of a third dimension (substratum depth) alleviates this negative impact. Coralline substratum samples exposed to average field grazing pressure tend to harbor a more diverse cryptofaunal community than is present in substrata protected from grazers. The presence of a third dimension appears to give the epilithic and cryptobiotic components the protection from grazers necessary for survival. Depopulation and recolonization studies conducted on an isolated Hawaiian patch reef suggests that the MacArthur-Wilson theory of island biogeography models the observed fish recolonization. The calculated wet biomass of fishes prior to depopulation was about 930 kg/ha which is in the range of other published studies. Fish community structure was dominated by planktivores (55% by weight) followed by carnivores (32%), herbivores (12%) and omnivores (2%). The large standing crop of planktivores was related to abundant plankton probably caused by local nutrient enrichment. Recolonization studies demonstrate that parrotfishes are one of the most successful groups to recolonize, suggesting that they are opportunistic in their habitat selection. A comparison of these data to those from the same reef 11 years earlier indicates that the structure of this community has been stable and has persisted in spite of local environmental change. Description: Thesis (Ph. D.)--University of Washington, 1979. Bibliography: leaves [114]-126. hdl.handle.net
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Sessile Invertebrate Colonization of a Coral Patch Reef: A Study of Two Reefs in Kaneohe Bay, Hawaii

T11 — Sat, 12 Jun 2010 16:02:37 +0000

Title: Sessile Invertebrate Colonization of a Coral Patch Reef: A Study of Two Reefs in Kaneohe Bay, Hawaii Author(s): Lewis, Clark R Abstract: Marine invertebrate colonization for a complete annual cycle was examined on two coral patch reefs in Kaneohe Bay, Oahu, Hawaii. Polyvinyl chloride panels provided the substratum for settlement and their placement on the reefs was along windward to leeward (upstream to downstream) transects. Counts of individual organisms and area covered by colonies provided data for site by site and inter-reef comparisons of temporal and spatial colonization trends. Over 80% of the total invertebrate settlements could be ascribed to five taxonomic groups: oysters, barnacles, serpulid worms, bryozoans, and tunicates. The patterns of colonization exhibited by these five groups are analyzed and discussed in detail. The greatest numbers of new settlements consistently occurred at the shallow windward site of each reef, whereas the least amount of colonization took place in the middle of the study reefs. These colonization phenomena are discussed with respect to the influence of various physical and biological factors. Five months into the study, all of the fishes were removed from the smaller of the two patch reefs, providing at least temporarily, a means of examining the effects of fish on invertebrate colonization. Visual transects were used prior to and after fish removal to assess the resident fish population. Due to the rapid recolonization of the reef, particularly by dominant herbivores, major effects on invertebrate colonization patterns were not detected. hdl.handle.net
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2010 El Nino Reduces Marine Life

T11 — Sat, 12 Jun 2010 16:02:23 +0000

The ongoing El Niño of 2010 is reducing numbers of pelagic fish along the California coast. news.scubatravel.co.uk
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Hamlet fish sheds light on evolution

T11 — Sat, 12 Jun 2010 16:02:21 +0000

SCUBA divers record distribution of reef fish and help make evolution discovery. news.scubatravel.co.uk
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