Bori L. Olla

Social enhancement of foraging on an ephemeral food source in juvenile walleye pollock, Theragra chalcogramma

SynopsisThe foraging effectiveness of walleye pollock juveniles, Theragra chalcogramma, was determined experimentally to test the hypothesis that social cues may facilitate the ability of individuals to exploit ephemeral food patches. Fish were tested when isolated, paired with one other fish, and in a group of six fish. Test fish exploited more food patches while in a group of six than when they were isolated. Patch exploitation by paired fish was intermediate to but not statistically different than isolate or grouped treatments. The number of pellets eaten by test fish in a group and a pair was more than 3.5 times that of when they were isolated, although the overall relationship between the amount of food eaten and group size was not statistically significant. Results support the hypothesis that juvenile walleye pollock exploit ephemeral food patches more effectively in the presence of conspecifics. In planktivores such as walleye pollock, social cues may enhance foraging on transient food sources either by facilitating detection of food patches (local enhancement) or by stimulating foraging activity when a food patch is located (social facilitation).

Thresholds for detection and feeding behavior in the dungeness crab, Cancer magister (Dana)

Abstract After observation and description of feeding behavior, the chemosensory ability of the Dungeness crab, Cancer magister (Dana) was measured with sea-water solutions of a freeze-dried extract of the littleneck clam, Protothaca staminea (Conrad). An abrupt change in antennular orientation accompanied by a specified increase in the antennular flicking rate indicated that a crab detected the food extract. The threshold concentration at which 50% of the crabs detected the clam extract was 10 −10 g/l At 10 −2 g/l crabs probed the substratum with the chelae and/or showed other feeding behavior. The chemosensory abilities of the Dungeness crab were compared with those of other crustaceans.

Photoreactivation in two closely related marine fishes having different longevities

The tautog, Tautoga onitis, and cunner, Tautogolabrus adspersus, are marine fishes which are closely related taxonomically (family Labridae), have similar habits, the same ecological requirements and are found in the same areas. However, they differ markedly in their longevity. The tautog is longer-lived, reaching an estimated average age of 34 years. It attains sexual maturity at 3--4 years of age. The cunner, on the other hand, lives to about 5--6 years of age and is sexually mature at about one year. An examination of their respective capacities for photoreactivation using cells in tissue culture derived from these fishes revealed marked differences in the rate of monomerization of ultraviolet-induced pyrimidine dimers from their DNA. Radiochromatographic analysis of dimers in the tautog showed that half the dimers were removed within a period of 10 min of exposure to photoreactivating light whereas a 50-min exposure was required to photoreactivate dimers to this same level in the cunner. Dark repair of dimers was measured by radiochromatography and by endonuclease assay. The two methods showed similar low levels of excision repair in both species.

Effects of oiled sediment on the burrowing behaviour of the hard clam, Mercenaria Mercenaria

Abstract The burrowing behaviour of juvenile hard clams, Mercenaria mercenaria , in oil-contaminated sediment was examined in a series of laboratory experiments. At oil concentrations within the range that might occur after an oil spill, depth and rate of burrowing were altered. The depth to which clams in oiled sediment burrowed after 96 h was significantly shallower than the depth in the controls, while the time taken to burrow beneath the surface was longer in oil-contaminated sediment. Alterations in burrowing were indicative of avoidance behaviour rather than oil-induced debilitation. The results suggest that such alterations may increase the vulnerability of this species to predation.

Excision repair of ultraviolet- and chemically-induced damage in the DNA of fibroblasts derived from two closely related species of marine fishes☆☆☆

Abstract The ability of an organism to modify chemical damages is an important factor in studies of the effect of xenobiotics on aquatic systems. We have examined the capacity of fibroblasts from two closely-related marine fishes, the tautog and the cunner, for excision repair of UV- and chemically-induced damage in their DNA. Two different assays, bromodeoxyuridine photolysis and the ara-C repair inhibition assay were used to demonstrate the levels of both ultraviolet and chemical excision repair are extremely low in these cells compared to that seen in normal human fibroblasts. In addition, while the levels of repair of N-acetoxyacetyl-aminofluorene (N-AAAF) and ethyl methanesulfonate damage are about the same in both fish, interesting differences were seen between the two species in the levels of repair of 4-nitroquinoline-1-oxide, methyl methanesulfonate and UV-induced lesions.

The burrowing behavior of sand lance, Ammodytes hexapterus: Effects of oil-contaminated sediment

Abstract Whilst foraging in the water column for zooplankton, sand lance, Ammodytes hexapterus , are under heavy predation from marine birds and fish. To avoid predation, sand lance bury in the sand when not foraging and during overwintering. We did two experiments to determine whether oil contamination of the sand would reduce the amount of time that sand lance spent buried. In the first experiment (June, 1980) sand lance significantly decreased by 20% the time spent buried in oiled sand (306 ppm). In the second experiment (June, 1981) sand lance did not decrease time spent buried in oiled sand at 28 and 256 ppm but did at 3384 ppm. The higher condition index of the 1981 fish suggested that nutritional state may have influenced how sand lance used the sediment as a refuge and how they responded to contamination of that refuge.

Effect of temperature on activity and social behavior of the adult tautog Tautoga onitis under laboratory conditions

Experiments were conducted on the effects of high, sublethal temperature on activity, social behavior, and feeding in the adult tautog Tautoga onitis held under controlled laboratory conditions. Norms of these behaviors were established during acclimation to temperatures at which these fish are commonly found. During acclimation, the fish were active and feeding throughout the day. A dominance hierarchy, based primarily on size, was established for each group, with subordinate fish being displaced from all areas of the aquarium. Under elevated temperature, changes in established norms of these behaviors were observed, with activity, feeding, aggression, and the spacing between fish showing a decrease. Following return to pre-rise temperatures, although aggression remained reduced, activity, interfish distance, and feeding approached levels established during acclimation. A comparison of these results with previous ones on young tautog is made and the significance of the findings is discussed.

Chemoreception in the food-searching and feeding behavior of the red hake, Urophysics chuss (Walbaum)

Abstract Behavioral observations were made of hake, Urophycis chuss (Wa,baum), presented with a freeze-dried clam extract over a wide concentration range. The silent food searching behaviors observed were emerging from shelter, swimming, and extending the chemosensitive modified pelvic fins over the bottom. Some fish also snapped at the source of extract-laden sea water. As the extract concentration increased, the three food searching behaviors occurred in more individuals and more concurrently in the same individuals. Above 10 −9 g·1 −1 , the percentage of hake showing the three food-searching behaviors and snapping increased linearly with the logarithm of the extract concentration. Detection was inferred from emergence from shelter or extension of pelvic fins. The threshold concentration at which 50% of the hake showed the behaviors indicating detection was 10 −8 g·1 −1 . The thresholds for food searching and snapping were 10 −7 g·1 −1 , respectively. The amounts of time spent swimming and moving the pelvic fins over the bottom were power functions of the food extract concentration. For hake, variation in one sensory input, strength of a chemical food cue, largely determined the onset and duration of food searching and feeding behavior.

Role of temperature in triggering migratory behavior of the adult tautog Tautoga onitis under laboratory conditions

Adult tautog Tautoga onitis, a marine temperate-water labrid, migrate each fall from inshore summering grounds to offshore overwintering sites. In a previous laboratory study, when adults were held under natural fall-winter cycles of temperature and photoperiod, changes in behavior, indicative of migration, occurred at the same time as their fall migration in nature. In the present study when fish were held under natural photoperiod in summer but with decreasing fall-winter temperature, while highly variable and transient components of migratory behavior were observed, no sustained trend was evident. Then, in the fall, under a naturally changing photoperiod but at simulated summer temperature, no trace of migratory behavior was observed. These findings indicate that temperature appears to play a leading role in triggering the fall migration of the species. The significance of these results and their ecological implications is discussed.

Characterization of the Physiological Stress Response in Lingcod

Abstract The goal of this study was to describe the duration and magnitude of the physiological stress response in lingcod Ophiodon elongatus after exposure to brief handling and sublethal air stressors. The response to these stressors was determined during a 24-h recovery period by measuring concentrations of plasma cortisol, lactate, glucose, sodium, and potassium. Lingcod were subjected to brief handling followed by either a 15-min or a 45-min air stressor in the laboratory. After the 15-min stressor, an increase in cortisol or glucose could not be detected until after 5 min of recovery. Peak concentrations were measured after 30 min for cortisol and after 60 min for glucose and lactate. Glucose and lactate had returned to basal levels after 12 h, whereas cortisol did not return to basal levels until after 24 h of recovery. Immediately following a 45-min air stressor, all measured parameters were significantly elevated over levels in prestressor control fish. Cortisol concentrations tended to increase ...