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A population of the characid Astyanax fasciatus was found living at the outflow of a subterranean source of water. Field observations revealed differences in behavior when compared with river populations. Affinity of this fish for the subterranean cavity was evidenced by behavior and distribution of individuals. Fish almost always carried bait into the subterranean cavity prior to feeding and also went into the cavity at night. Three factors may influence the affinity for the subterranean source of water: 1) protection against aerial predation, 2) the advantage to fishes of hovering in shade, 3) sheltering for reproduction. These observations suggest that cave colonization may take place actively rather than accidentaly, that behavioral changes may preceed morphological ones during initial stages of cave entry, and that behavioral adaptations may occur quite rapidly.

Like countless other vertebrates and even many invertebrates, blue gouramis, Trichogaster trichopterus, a freshwater tropical fish, can learn to associate environmental cues with the appearance of biologically important events. Research with blue gouramis reveals that this capacity for learning, which psychologists call Pavlovian conditioning, provides the means to enhance their territorial defense as well as reap large reproductive benefits. That is, males are able to defend their territories more efficiently when the appearance of a rival is signaled than when territorial invasion is less predictable. Not only does signaling enable Pavlovian-conditioned males to mount a more aggressive defense of their territories than males that do not have the benefit of signaling, but it helps them to concentrate their efforts at times when, or places where, the territory is most vulnerable. In addition, both males and females can learn to anticipate the appearance of a mate. Signaling of female accessibility enables Pavlovian-conditioned males to attenuate their initial aggressive response to arriving females without compromising their territorial defense. More important, when the arrival of a potential mate is signaled, Pavlovian-conditioned males are able to spawn with females sooner, clasp females more often, and produce more young than males that do not have the benefit of a signal. The ability of blue gouramis, among many other fish, to anticipate the appearance of such different biologically important events suggests that Pavlovian conditioning may play a significant role in their behavioral ecology. In addition, conditioning may provide a useful tool in several practical domains, including animal husbandry, zoological management, and conservation biology.

A technique for enhancing growth bands on vertebrae was assayed using 477 centra from blackmouth catsharks, Galeus melastomus. Specimens were caught at depths between 200 and 800 meters off the southern Portuguese coast (Algarve) during an IPIMAR research cruise in August 1994. Total lengths ranged from 12 to 71 cm. Standard vertebral ageing techniques, such as silver nitrate impregnation, haematoxylin staining, grinding and shading failed to produce clearly contrasting bands. A method solely based on vertebra decalcification with nitric acid (5%) yielded the most satisfactory results. This technique provided clear band differentiation and was used by two independent readers. The analysis of differences in band counts between readers was based on: percent of disagreements, percent of disagreement by length group, index of average percent error and Wilcoxon's signed ranks test. The majority of differences corresponded to only one band of disagreement and disagreements have been found to increase with length, which stresses the need for a larger sampling effort on the larger and older individuals. The index of average percent error was estimated as 4.6% and no statistical differences were detected between readers' results.

Field and laboratory experiments indicate that the mottled sculpin, Cottus bairdi, feed in the dark. Blinded sculpins feed on a variety of motile prey in the laboratory and show stereotyped responses to prey stimuli. The sculpins bite at moving inert objects, even if buried in substratum, indicating that they use their lateral line system to detect prey. Covering portions of the lateral line with an inert paste eliminates response to objects near the covered region of the lateral line. The sculpins can also detect prey (including inert objects) in a stream if the prey is upstream. Collection from two series of presunset, postsunset, presunrise, postsunrise, dives in Lake Michigan indicate nocturnal feeding by the mottled sculpin.

Sedimentation in aging reservoirs generally reduces fish habitat quality and quantity, often isolating coves and pools from the main body of the reservoir. In some cases, however, habitat fragments created by sediment deposition in the river-reservoir interface zone support high fish diversity, and they could potentially replicate features of nursery habitats in natural river floodplains if they are regularly connected to the greater river-reservoir. We examined the structure of larval fish assemblages in fragmented coves and pools within the transitional zone of an aging reservoir (Lake Texoma) over 2 years with contrasting hydrological conditions (dry year with low connectivity versus wet year with high connectivity to the main body of the reservoir). We found that larval assemblage structure varied spatially across the two river arms of the reservoir and temporally across the dry and wet year. In both years, assemblages were dominated by Dorosoma species and Menidia beryllina, taxa considered habitat generalists. The abundance of other taxa, particularly Lepomis, Pomoxis, and Morone species, increased with greater habitat connectivity in the wet year. Many taxa considered dependent upon riverine or floodplain habitats were collected during the wet year at sites where they had not been collected in the dry, low-connectivity year. Our results suggest that these fragmented habitats can provide nursery habitats for a variety of fish taxa, but that the structure of larval assemblages using them varies widely based on hydrological connectivity.

Green razorfish are Caribbean wrasses that live in harems on shallow sand or seagrass beds, which offer little cover for predator avoidance (PA). Field observations showed that non-conspecific fishes that intruded were either attacked, ignored, or actively avoided. Food competitors and small piscivores were attacked by male razorfish. Razorfish PA behaviors varied among three habitats with different substratum compositions, suggesting that these fish possess phenotypic plasticity for PA behavior. In a rocky-rubble habitat, razorfish dove into the coarse sand for PA, but most sand dives observed there were to soften a small site for future PA. In a sandbed habitat, they hid among coral branches and dove into the sand when attacked; few maintenance dives were observed as soft sand was widespread. In a seagrass habitat, they hid among blades of grass for PA, and dove into the sand less frequently than at the other sites. Some female razorfish that were transferred among habitats adopted PA behaviors similar to those of females in the new site, while others did not, suggesting that behavioral plasticity is not universal in this species. Razorfish spawned lower in the water column in the presence of natural predators and a predator model, than when these were absent. When the predator model was introduced into a male's territory during spawning periods, there was a reduction in his courtship rate, but not in the number of spawns he achieved. Predation pressure may reduce males' long-term fitness by causing decreased courtship rates which can facilitate sex change in harem females.

Sự gia tăng dân số dự kiến dẫn đến nhu cầu thực phẩm tăng cao, ảnh hưởng nghiêm trọng đến tài nguyên thiên nhiên của Trái đất. Cải thiện năng suất cây trồng mà không làm ảnh hưởng đến môi trường sẽ là một trong những thách thức chính trong các thập kỷ tới. Trong số các biện pháp có thể thúc đẩy nông nghiệp bền vững, phân bón hữu cơ, đặc biệt là tảo, đang nhận được sự chú ý ngày càng tăng. Mục tiêu của nghiên cứu này là kiểm tra hai loại tảo lớn (Chaetomorpha sp. và Cystoseira sp.), một loại tảo nhỏ (Chlorella CH2) và Bioguano (hỗn hợp tảo lớn, spirulina và guano) như là phân bón hữu cơ cho sự phát triển của cây mầm lúa mạch. Sự tăng trưởng cây trồng đáng kể đã được ghi nhận ở Bioguano, với cây con cho thấy tổng năng suất sinh khối tương đương với các cây kiểm soát tích cực sử dụng phân bón hóa học. Tăng trưởng cây trồng trên tảo lớn bị giảm, mặc dù ở Chaetomorpha sp. không đáng kể so với nhóm kiểm soát tích cực. Tăng trưởng của cây trên Chlorella CH2 gần giống với nhóm kiểm soát tiêu cực (chỉ có nước). Cây trồng trên Bioguano đạt hiệu suất hấp thụ N (60%) và K (41%) cao. Cây trồng trên tảo lớn cho thấy hiệu suất hấp thụ N cao, và đặc biệt là P (khoảng 30%). Kết quả của chúng tôi gợi ý về tiềm năng cao của Bioguano và, ở mức độ thấp hơn, của tảo mà không cần áp dụng phân bón tổng hợp để sử dụng làm môi trường trồng cho cây.

Fresh and dry specimens of Sargassum polycystum and Laurencia obtusa were collected from the Seribu Islands waters, Indonesia, and crude methanol, diethylether and hexane extracts were tested for antioxidant activity using the thiocyanate method. None of the extracts of dry S. polycystum and L. obtusa showed antioxidant activity, but extracts of fresh material did show activity. L. obtusa extracts had higher antioxidant activity than those of S. polycystum. The methanol extract of S. polycystum was more active than the other extracts, and the n-hexane extract of L. obtusa was more active than the diethylether and methanol extracts.

Three methods of algal quantification (direct cell counts, chlorophyll a extraction, in vivo fluorescence) were used to evaluate the response of the unicellular green flagellate Tetraselmis suecica to nutrients and grazers. Nutrient enrichment enhanced total cell counts, chlorophyll a concentration and in vivo and DCMU-fluorescence. Photosynthetic efficiency was reduced in the complete F2 medium as indicated by the high level of in vivo fluorescence, whereas photosynthetic efficiency was increased by the introduction of mussels to the F2 medium. The addition of mussels significantly increased the proportion of non-motile cells, but did not reduce the total cell count. The effect of mussel grazing on algae could be underestimated if only total cells were counted or only the chlorophyll a concentration was measured. The results indicate that these three methods measure different properties of an algal culture and are complementary to each other in assessing the quality and quantity of an algal population. Direct algal counting offers a reliable numerical assessment for cell population abundance. Chlorophyll a concentration was closely correlated to the total cell count. In the presence of mussels, in vivo fluorescence did not correlate with either algal cell counts or chlorophyll a concentration, indicating that the measurement of in vivo fluorescence may be misleading for estimating algal abundance under different culture conditions.