Does breathing apparatus affect fish counts and observations? A comparison at three New Zealand fished and protected areas

Across three areas, open-circuit scuba (OC) and rebreather (RB) surveys produced similar results for the density and size distribution of fish species inside and outside marine reserves. At Tonga Island, more Notolabrus celidotus were counted with OC than with RB, independently of reserve status [log-scale response ratio of OC/RB (RR) = 0.7]. At Long Island, differences in abundance of Parapercis colias between sampling methods were small at reserve sites (RR = −0.1), but more were counted with scuba than with RBs at fished sites (RR = 0.5). RRs for Pagrus auratus were −1.0 in fished areas and 0.3 in the reserve at Leigh. We also sampled each site using a baited video system (BUV) to establish whether diver-transects sampled the full size range of target species. Most fish in BUV views were Parapercis colias at Long Island (97%), and Pagrus auratus at Leigh (77%). Size structures of Parapercis colias were similar among all three sampling methods within reserve and fished areas at Long Island (max. chi-squared distance = 0.11). BUV samples for Pagrus auratus at Leigh did not detect a prominent juvenile size class observed by divers, but size-frequency distributions of OC, RB, and BUV corresponded at sizes beyond 15 cm TL (max. chi-squared distance = 0.08). To investigate the effects of diver sound on fish behaviour at Long Island, we also compared fish activity when divers with RBs or scuba were present, when the sound of each breathing apparatus was replayed underwater, when no divers were present and no sound was replayed, and when bait was provided, within the reserve only. The lowest number of fish visits to the focal area (mean of 3.0 per 10 min) for Parapercis colias occurred with RB divers present. Maximum abundances of Parapercis colias in all speaker treatments averaged 4.1 per 10 min, whereas with scuba divers present maximum abundances were 5.7, and with baits the average was 38.0 per 10 min.     

In-situ observations of Baltic herring (Clupea harengus membras) spawning behaviour in the Askö-Landsort area,northern Baltic proper

In a Baltic herring (Clupea harengus membras L.) spawning ground study, carried out in summer 1982 in the northern Baltic proper, spawning herring were encountered on two line transects on June 14. The spawning behaviour of minor groups as well as of a large school was studied in situ by four divers for approximately three hours. No behavioural differences or systematic coordinated behaviour between the sexes could be detected. Most of the spawning took place in a limited depth interval, 0.5 to 4 m, and Ceramium tenuicorne was the substrate most used.     

Interactions between fangblennies (Plagiotremus rhinorhynchus) and their potential victims: fooling the model rather than the client?

Lepidophagous (scale-eating) blue-striped fangblennies (Plagiotremus rhinorhynchus Bleeker 1852) are often found sympatrically with the bluestreak cleaner wrasse (Labroides dimidiatus Valenciennes 1839). They have some resemblance to the juvenile L. dimidiatus and have previously been reported as aggressive cleaner wrasse mimics. We observed 14 P. rhinorhynchus on a small area in the barrier reef near Hoga Island, Indonesia to assess the effects of client size on the behaviour and attack success of fangblennies: our results suggest that fangblennies are selective with regard to victim size; fish avoided by the fangblennies are significantly larger than those not avoided and attack success is significantly higher at intermediate victim size classes. The behaviour of the victims also has a significant direct effect on the foraging success of the fangblennies; where the potential victim posed, 63.6% were ignored by the fangblenny and only 7.4% of attacks were successful on posing fish as opposed to a surprise attack success rate of 71.6%. Overall, victims which exhibited the pose behaviour were significantly smaller in size. It appears likely that the predatory strategy of these fangblennies varies with victim size and that mimicry plays a minor role in attracting potential victims. We suggest that in common with other mimetic fish the resemblance of fangblennies to juvenile bluestreak cleaner wrasse allows them to actively hunt in areas where adult cleaners are common thus, indirectly improving their feeding opportunities.     

Effects of relaxed predation pressure on visual predator recognition in the guppy

Many prey species have a genetic predisposition to recognise and respond to predators and can fine-tune their anti-predator behaviour following appropriate experience. Although the Trinidadian guppy ( Poecilia reticulata) has become a model species for the investigation of adaptive behaviour, the extent to which experience mediates predator recognition remains unclear. In this study, we examined the effects of relaxed predation pressure on patterns of anti-predator behaviour in populations differing in evolutionary history. The anti-predator behaviour of wild- and laboratory-born guppies from high- and low-predation localities in Trinidad were compared using three models resembling Crenicichla alta, a dangerous guppy predator, Aequidens pulcher, a less dangerous piscivore, and a snake. Snakes are not known to prey on guppies in Trinidad. Specifically, the following predictions were tested: (1) wild caught fish from the high-predation localities (where guppies co-occur with C. alta and A. pulcher) would respond to the three models according to their perceived level of threat, whereas guppies from the low-predation site would show a reduced response to all of the predator models; (2) high-predation laboratory-reared fish would display a reduced but qualitatively similar response to their wild counterparts; and (3) there would be no behavioural differences between wild- and laboratory-reared low-predation fish. In accordance with these predictions, the results revealed that wild fish originating from high-predation sites responded more strongly to the models than fish from low-predation sites. When reared in the laboratory, guppies from the high-predation population showed a reduced response compared to their wild-caught counterparts, but there was no difference in the behaviour of wild- and laboratory-reared low-predation fish. Model type affected predator inspection behaviour but not schooling tendency, and both wild- and laboratory-reared guppies were more wary of the fish models than the snake. These results suggest that early experience differentially mediates the anti-predator responses of fish from high-risk localities.     

Feeding and aggressive behaviours in juvenile coho salmon (Oncorhynchus kisutch) under chemically-mediated risk of predation

Summary Juvenile coho salmon (Oncorhynchus kisutch) spend the first year of their lives in their natal streams, where they may often hold feeding territories. They also face significant risk of predation by birds and fish, and should alter their behaviour to reduce risk of mortality when these predators are present. Although there is laboratory evidence that coho react to predator visual stimuli, chemoreception of avian predator presence has not previously been reported. We tested the influence of chemical stimuli of common merganser (Mergus merganser), preying on juvenile coho, on two aspects of coho territorial behaviour, foraging and aggression, in flow-through aquaria. After a mixture of merganser- and coho-conditioned water was introduced into the system, juvenile coho significantly reduced their attack distance on drifting prey. The fish also significantly decreased their aggressive behaviour directed towards mirrors (total number of acts, intensity of acts and time spent) when the same odour was present. They did not change their behaviour in either experiment after control introductions of water treated with fish alone. These results are interpreted within the framework of a trade-off between juvenile growth and mortality.     

Predator inspection behaviour in three-spined sticklebacks (<Emphasis Type="Italic">Gasterosteus aculeatus</Emphasis>): body size,local predation pressure and cooperation

The apparently maladaptive tendency of fish to approach and inspect potential predators has been explained in terms of useful information gathering or as a signal to the predator that it has been seen. We examined this behaviour in 16 populations of wild-caught stickleback (Gasterosteus aculeatus) from ponds with and without predatory perch (Perca fluviatilis). Three large and three small individuals per population were each exposed to three model predators differing in realism. A final cooperative treatment entailed pairing subjects with a second individual from the same population, but of the alternative size class, during predator presentation. As might be expected, predator inspection behaviour was much greater in the predator-sympatric populations, and only these fish increased their level of inspection as the models became incrementally more realistic. This suggests that reductions occur in the level of costly inspection behaviour in populations without predators. Subject body size had no effect on inspection effort, which suggests a limited role for experience (we assumed larger fish to be older than smaller fish), at least over the relative age differences utilized. However, small predator-sympatric fish were the only subjects to increase inspection significantly when in a cooperative context, perhaps reflecting the inherent value of a relatively larger partner in this context. These results confirm that levels of predator inspection are both population- and situation-dependent, suggesting a trade-off in the potential costs and benefits of this behaviour.Communicated by C. St. Mary     

Light intensity and the feeding behaviour of herring,Clupea harengus

An infra-red sensitive video-recording technique was used to study the effects of darkness and light intensities from 0.0001 to 270 photopic lx on the feeding behaviour of herring (Clupea harengus L.). When offered natural zooplankton, consisting of a mixture ofCalanus finmarchicus, Euchaeta norvegica, Oithona similis, Balanus sp. nauplii, and crustacean nauplii as prey, the fish fed by biting (snapping) at light intensities above a threshold of 0.001 lx and were size-selective, taking the larger organisms first. When fed on pure cultures of CaliforniaArtemia sp. nauplii (San Francisco Bay brand), the threshold light intensity was 0.01 lx. Swimming speed increased with increasing light intensity when the fish were actively feeding by biting. When the fish were filter-feeding on high densities ofArtemia sp. nauplii in the light, they continued to school and swimming speed was not related to light intensity.     

Herring (Clupea harengus) filter-feeding in the dark

The behaviour of juvenile herring (Clupea harengus L.) feeding on Artemia sp. nauplii in both light and dark was recorded using an infra-red-sensitive television-recording technique. In the light, two modes of feeding were observed, particle biting and filtering, but in the dark only filtering was observed. Marked differences in swimming behaviour were seen between light and dark. In the light, the fish continued to school while feeding in both modes; in the dark, the school dispersed, the fish swam slower in tight circular paths and fed only by filtering. In the dark, filtering fish swam faster (0.11 m s^-1) than non-filtering fish (0.07 m s^-1). In the light, no difference in speed was measured between filtering and non-filtering fish (0.34 m s^-1). Owing to the lower filtering speeds in the dark, the removal rate of nauplii from the water was much lower than in light, except in the highest prey concentrations. This suggests that if night-time filter-feeding takes place in the sea, it will be of importance only when exploiting dense patches of food.     

Foraging behaviour of sympatric Antarctic and subantarctic fur seals: does their contrasting duration of lactation make a difference?

The duration of periods spent ashore versus foraging at sea, diving behaviour, and diet of lactating female Antarctic (Arctocephalus gazella, AFS) and subantarctic (A. tropicalis, SFS) fur seals were compared at Iles Crozet, where both species coexist. The large disparity in lactation duration (SFS: 10 months, AFS: 4 months), even under local sympatry, has led to the expectation that AFS should exhibit higher foraging effort or efficiency per unit time than SFS to allow them to wean their pups in a shorter period of time. Previous evidence, however, has not supported these expectations. In this study, the distribution of foraging trip durations revealed two types of trips: overnight (OFT, <1 day) and long (LFT, >1 day), in common with other results from Macquarie Island. However, diving behaviour differed significantly between foraging trip types, with greater diving effort in OFTs than in LFTs, and diving behaviour differed between fur seal species. OFTs were more frequent in SFS (48%) than in AFS (28%). SFS performed longer LFTs and maternal attendances than AFS, but spent a smaller proportion of their foraging cycle at sea (66.2 vs. 77.5%, respectively). SFS dove deeper and for longer periods than AFS, in both OFTs and LFTs, although indices of diving effort were similar between species. Diel variation in diving behaviour was lower among SFS, which foraged at greater depths during most of the night time available than AFS. The diving behaviour of AFS suggests they followed the nychthemeral migration of their prey more closely. Concomitant with the differences in diving behaviour, AFS and SFS fed on the same prey species, but in different proportions of three myctophid fish (Gymnoscopelus fraseri, G. piabilis, and G. nicholsi) that represented most of their diet. The estimated size of the most important fish consumed did not vary significantly between fur seal species, suggesting that the difference in dive depth was mostly a result of changes in the relative abundance of these myctophids. The energy content of these fish at Iles Crozet may thus influence the amount and quality of milk delivered to pups of each fur seal species. These results contrast with those found at other sites where both species coexist, and revealed a scale of variation in foraging behaviour which did not affect their effort while at sea, but that may be a major determinant of foraging efficiency and, consequently, maternal investment.     

Metals in the sediment and liver of four fish species from different trophic levels in Tisza River,Serbia

In aquatic environments metals originate from various natural and anthropogenic sources. The degree of contamination in fish tissues depends on the pollutant, fish species, their mode of feeding, sampling site and trophic level. This study presents concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Sr and Zn in sediment and liver of four ecologically different fish species: piscivorous northern pike (Esox lucius L.), benthivorous sterlet (Acipenser ruthenus L.) and silver bream (Brama brama L.), and omnivorous common carp (Cyprinus carpio L.). Fish were caught at four sites along the stretch of the River Tisza in Serbia during October 2010. The concentrations of metals have been assessed using the inductively coupled plasma – optical emission spectrometry. Results revealed that metals with the highest values in sediment and fish samples were Al and Fe, respectively and sometimes concentrations of Zn are in the same order of magnitude as Fe concentrations. The highest concentration of metals was recorded in omnivorous common carp.     

Methylmercury, total mercury and total selenium in four common freshwater fish species from Ya-Er Lake, China

Snakehead fish (Ophiocephalus argus cantor), silver carp (Hypophthalmichthys molitrtix), crucian carp (Carassius carassius), and common carp (Cyprinus carpio) are four common freshwater fish species in China. In this study, the level of methylmercury (MeHg), total mercury (T-Hg), and total selenium (T-Se) in muscle samples of these four fish species from Ya-Er Lake, China, were analyzed using atomic fluorescence spectrometry coupled with high-performance liquid chromatography, and inductively coupled plasma mass spectrometry. The concentrations of MeHg in all the fish species were significantly correlated with those of T-Hg. Higher T-Hg and MeHg concentrations had accumulated in the snakehead fish, which is a strongly predatory fish, than in the other three species. The concentration ratios of MeHg and T-Hg in the muscles of these four fish species were almost equal. Conversely, there was negative correlation between the concentrations of T-Hg and T-Se, which implies that there is a competition between these two elements with respect to bioaccumulation. It is noteworthy that of all the muscle samples tested, the level of T-Hg exceeded the maximum allowable limit in fish [0.4 mg kg⁻¹ (w/w) recommended by the World Health Organization] in 38.46% of those of the silver carp, 18.18% of those of the crucian carp, and 100% of those of snakehead fish. These results show that the consumption of contaminated fish is a potential threat to human health and that necessary preventive measures to safeguard public health should be emphasized.     

Predator-induced alarm responses in the common periwinkle, Littorina littorea: dependence on season, light conditions, and chemical labelling of predators

Chemically mediated alarm reactions of the common periwinkle, Littorina littorea (L.), were studied in laboratory experiments during two consecutive summers, and one intermediate autumn season. Responses to chemical stimuli were detected as crawl-out responses, i.e. movements of snails out of the water. Snails were exposed to extracts of injured conspecifics, extracts of the mussel Modiolus modiolus (L.), and water conditioned by the predatory crab Carcinus maenas (L.), which had been maintained on different diets. In experiments carried out during the summer, a significantly larger number of snails moved out of the water when exposed to chemical stimuli from injured conspecifics, compared to chemical stimuli from injured mussels or filtered seawater. These results suggest that chemical alarm substances are present in L. littorea. Water conditioned by crabs that had been fed L. littorea released significantly more crawl-out responses compared to water conditioned by crabs that had been kept on a fish diet. When tested in autumn, no significant differences were found in responses to the above-mentioned water samples. Crawl-out responses under different light regimes were also investigated. All series of experiments carried out in the dark evoked a higher number of responses compared to series that took place in light. These findings may indicate an adaptation of snails to night-active predators. In total, the current results suggest that a L. littorea diet may chemically “label” the predator crab with snail alarm substances, and that predator-induced responses of L. littorea are actually responses to conspecific alarm substances released from crabs that have been maintained on a L. littorea diet. The response to the alarm signal, however, appears to be dependent on season and light conditions; some ecological implications of these findings are also discussed. Received: 8 January 1999 / Accepted: 29 March 1999     

Anthropogenic influences on the infestation of intertidal gastropods by seabird trematode larvae on the southern Barents Sea coast

In this study we examined how the variation in the distribution of six species of seabird trematodes was influenced by human activities along the subarctic Barents Sea coast of northern Norway. This was done by comparing the prevalence of the parasites in two species of intermediate host (Littorinasaxatilis and Littorina obtusata) on seashores near fishing industry complexes, fish farms and at control sites. In L. saxatilis there were higher prevalences at sites influenced by human activities for three out of five trematode species (Microphallus piriformes,  M. similis, Cryptocotyle lingua) which have gulls (Larus spp.) as their predominant final hosts, while in L. obtusata, only  M. similis was more common at sites with human activity. For  M. pygmaeus, a trematode which has the common eider (Somateria mollissima) as its most predominant final host, the prevalence in L.␣saxatilis tended to be higher at sites with fishing industry, but differences were not significant. No such tendency was found in L. obtusata for this trematode. The overall prevalence in L. obtusata was lower than in L.␣saxatilis. This indicates that the vulnerability to trematode infection differs between the two snail species depending on the variation in the distribution patterns in the intertidal zone. Gulls tend to concentrate in areas near fishing industry and fish farms to feed on fish offal, which leads to an increase in the transmission between hosts, and to a higher level of parasite infection, locally. Received: 4 May 1998 / Accepted: 18 October 1998     

Acoustic orientation in the palmate newt, Lissotriton helveticus

Experiments reported here were carried out to investigate the use of acoustic cues by palmate newts (Lissotriton helveticus) for orientation and to study whether this behavior is learned, or whether two populations of palmate newts that cohabit with different frog species (Iberian green frog, Rana perezi, and European common brown frog, Rana temporaria) show different phonotactic preferences. The orientation tests consisted of presenting a control stimulus (white noise), a sympatric acoustic stimulus (calls of R. perezi or R. temporaria, depending on the origin of newts), or an allopatric stimulus (calls of natterjack toads, Bufo calamita, or R. perezi). Newts were released in a circular arena, while the acoustic stimuli were presented outside of the circular arena in four different compass orientation directions (0, 90, 180 and 270°). In this study, we show that L. helveticus performed positive phonotaxis toward the calls of R. perezi only when both species shared habitat, orienting randomly when R. perezi was absent from the newt’s natal population. Newts from both populations oriented randomly when exposed to the allopatric and control acoustic stimuli. These results suggest, for the first time, that recognition of the sympatric heterospecific calls could be learned. However, newts sharing the breeding pond with a population of R. temporaria oriented randomly when exposed to the calls of this species. The fact that the breeding seasons of R. temporaria and L. helveticus do not overlap in time does not allow the use of R. temporaria calls as a guidance mechanism for migrating individuals of L. helveticus.     

Isolation of cellulolytic microbes from the intestinal tract of the pinfish,Lagodon rhomboides: size-related changes in diet and microbial abundance

Pinfish, Lagodon rhomboides (Linneaus), undergo a gradual ontogenetic dietary shift during their first year of life, marked by an increase in the consumption of plant material. To determine if this shift in diet was associated with a change in the microbial flora of the intestinal tract that may assist in degradation of plant material, stomach contents were analyzed and microbes in the intestinal tract were isolated from fish ranging from 20 to 139 mm standard length. These fish were collected from Core Sound, North Carolina, USA between March and September 1991. Plant material increased from 16% of dry weight of stomach contents in pinfish under 40 mm standard length (SL) to 65% in pinfish above 120 mm SL, confirming previous observations of a diet-related ontogenetic change in L. rhomboides. Comparison of the total cultivatable facultative and anaerobic microbial flora isolated from the intestinal tract contents of pinfish ranging in size from 26 to 139 mm SL showed a 10-fold increase between fish <40 and fish >40 mm SL, with maximum population densities of approximately 2x10⁷ colony forming units (CFU) g^-1 of intestine including contents. The percentage of microbial isolates examined capable of hydrolyzing carboxymethylcellulose (CMC) increased from 12% in fish <40 mm SL to 13 to 50% in fish >40 mm SL, although there was no strict increase with increasing fish size classes. Although the percentage of CMC-hydrolytic microbial isolates varied with respect to fish SL, the percentage of skim-milk hydrolytic (proteolytic) isolates remained relatively constant (4% of total isolates) irrespective of fish SL and dietary composition. Results presented in this study document the first isolation of carboxymethylcellulase producing microbes from the intestinal tract of any fish and demonstrate that the ontogenetic dietary shift in L. rhomboides is paralleled by qualitative and quantitative changes in the intestinal microbial community. The use of strict anaerobic sampling methods in the preparation of intestinal contents from wild-captured fresh specimens was essential in obtaining these isolates.     

Feeding ecology of the piscivorous birds Phalacrocorax varius,P. melanoleucos and Sterna bergii in Moreton Bay,Australia: diets and dependence on trawler discards

The diets of three piscivorous bird species from Moreton Bay, Queensland, Australia, were monitored for 14 mo from April 1986 to September 1987. Regurgitated pellets from Phalacrocorax varius (pied cormorant), P. melanoleucos (little pied cormorant) and Sterna bergii (crested tern) were collected monthly and prey items were identified from otoliths, spines and whole-fish remains. Otolith weight to fish length and weight relationships were used to aid in calculation of diet composition. Sepia sp. was the commonest prey of P. varius and P. melanoleucos; Sterna bergii took few Sepia sp. In order of decreasing importance, the teleosts Sillago maculata, Apogon fasciatus and Leiognathus moretoniensis were the next most common prey in all diets. P. melanoleucos has previously been reported to eat primarily crustaceans. The size ranges of fish prey were 18 to 452 mm for P. varius; 25 to 246 mm for P. melanoleucos; and 33 to 226 mm for Serrna bergii. The three species had similarly narrow diets. There was a significant rank correlation between the diet of P. varius and the by-catch of the prawn trawlers. This, together with observations of feeding behaviour, the similarity of the diets and the benthic and benthopelagic nature of most prey species, suggests that in Moreton Bay the three bird species are primarily dependent on food from fishery discards. The population of about 350 P. varius possibly consumes 13.7% of the total fish by-catch. The relationships between the fishery and the piscivorous birds in discussed in relation to size of bird populations and its possible dependence on the fishery.     

Pheromone-based aggregation behaviour of the firebrat, <Emphasis Type="Italic">Thermobia domestica</Emphasis> (Packard) (Thysanura: Lepismatidae)

Summary. We tested the hypothesis that aggregation behaviour of the firebrat, Thermobia domestica (Packard) (Thysanura: Lepismatidae), an inhabitant of enclosed microhabitats, is mediated, at least in part, by a pheromone. Individual insects were released into the central chamber of a 3-chambered olfactometer and test stimuli were placed in lateral chambers. Paper discs previously exposed for 3 days to 10 female, male, or juvenile T. domestica were all preferred by female, male, or juvenile T. domestica over unexposed paper discs, indicating the presence of an aggregation/arrestment pheromone. In additional experiments, frass and scales from female T. domestica, tested singly and in combination, proved not to be the source of the pheromone. Physical contact was required for pheromone recognition, indicating that the pheromone arrests rather than attracts conspecifics. Arrestment by the long-tailed silverfish, Ctenolepisma longicaudata Escherich (Thysanura: Lepismatidae), but not by the common silverfish, Lepisma saccharina L. (Thysanura: Lepismatidae), to T. domestica exposed paper discs suggests closer phylogenetic relatedness between C. longicaudata and T. domestica, than between C. longicaudata and L. saccharina. Whether C. longicaudata or L. saccharina produce an aggregation signal, and whether T. domestica respond to this signal is unknown. Received 10 June 2002; accepted 30 September 2002.     

Predator evasion in a fish school: test of a model for the fountain effect

A model to explain the behavioural mechanisms underlying the fountain manoeuvre, a predator-evasion response shown by fish shoals is tested. It is proposed that the responses of individual fish are constrained by requirements to (1) visually monitor the predator's behaviour, (2) minimise the energetic cost of escape, and (3) maximise the rate of passage around the predator. The model predicts that individuals will swim away from the threat at a constant angle determined by the rear limit of the visual field and that the range of reaction will be constrained by water visibility. The model's predictions were upheld in tests conducted in 1984 using a shoal of juvenile whiting, Merlangius merlangus (L.). It is concluded that the principal determinant of the fountain manoeuvre is the visual field of the fish.     

Effects of subchronic exposure to carbofuran on antioxidant defence system and malondialdehyde levels in common carp (Cyprinus carpio L.)

The present study focused on the assessment of oxidative stress induction by pesticides such as carbamates which are widely used as insecticides and nematicides and contaminate aquatic ecosystems on certain biomarkers in liver of common carp (Cyprinus carpio L.). Biomarkers selected for stress monitoring were malondialdehyde (MDA), an index of lipid peroxidation, and antioxidant defence system enzymes, mainly catalase (CAT), glutathione reductase (GR), and glutathione-S-transferase (GST) activities in liver of fish exposed to 0, 10, 50, or 100?µg?L^?1 of carbofuran for 4, 15, or 30 days. Oxidative stress was found in liver of common carp exposed to carbofuran which was manifested by a decrease in CAT and GR activities after 4 and 30 days of exposure. An adaptive response was probably produced since at day 15 no modifications in the CAT activity and increased GR activity were observed. In addition, a decrease in MDA content with the highest concentration of carbofuran used was found after 30 days of exposure. However, no significant changes were found in GST activity showing a varied response. The results concerning oxidative and antioxidant profiles indicate that subchronic exposure to the insecticide carbofuran is capable of inducing oxidative stress in fish.     

Altered c-Fos expression demonstrates neuronal stress in mummichog, <Emphasis Type="Italic">Fundulus heteroclitus</Emphasis>, exposed to <Emphasis Type="Italic">Pfiesteria shumwayae</Emphasis> and <Emphasis Type="Italic">Chaetoceros concavicornis</Emphasis>

To better understand sublethal effects of harmful algal blooms (HABs) on fish, mummichog, Fundulus heteroclitus (L.), were exposed in the laboratory to varying, environmentally relevant densities of Pfiesteria shumwayae (Glasgow et Burkholder, CCMP 2089, dinoflagellate) and Chaetoceros concavicornis (Mangin, CCMP 169, diatom). Two experiments were conducted during the spring of 2003 and 2004 to quantitatively examine the effects of acute (2 h) P. shumwayae and C. concavicornis algal exposure on mummichog brain activity using c-Fos expression as a marker of altered neuronal activity. Brains from HAB-exposed fish were removed, sectioned, and stained using immunocytochemistry prior to quantifying neuronal c-Fos expression. Fish exposed to P. shumwayae and C. concavicornis showed increased c-Fos expression compared to unexposed control fish. A significant dose-response relationship was observed, with increased labeling in brains of fish exposed to higher cell densities for both HAB species tested (P ≤ 0.01). Increased labeling was found in the telencephalon, optic lobes, midbrain, and portions of the medulla. The greatest increases in expression were observed in the telencephalon of P. shumwayae-exposed fish, and in the telencephalon and optic lobes of C. concavicornis-exposed fish (P ≤ 0.01). These increases in c-Fos expression are consistent with other physical and chemical stress exposures observed in fish. Neuronal stress, evidenced by c-Fos expression, demonstrates a sublethal effect of exposure and changes in brain activity in fish exposed to HAB species.