Stability of behavioral syndromes but plasticity in individual behavior: consequences for rockfish stock enhancement

This study investigated behavioral syndromes, which are defined as correlations between behaviors. Behavioral syndromes can lead to the unintentional alteration of a wide range of behavioral traits of hatchery fish if unintentional selection on one behavior leads to selection on a correlated behavior. Specifically, this study used brown rockfish, Sebastes auriculatus, to test the hypothesis that a fish that feeds at high rates in the absence of a predator also takes more risks when a predator is present, and that through such a correlation, unintentional hatchery selection for high feeding rates may also lead to changes in risk taking behavior (here defined as behavior that increases predation risk). Behavioral syndromes were found—feeding behavior in the absence of a predator tended to correlate positively with both feeding behavior in the presence of a predator model and time near the model. These syndromes were stable through time—that is, the same correlations appeared 10 days later when the behavioral assays were repeated. However individual behavior was inconsistent (plastic). A fish could both feed and take risks at high rates on Day 1, but then both feed and take risks at low rates on Day 10. Thus, while behavioral syndromes were stable (i.e. present in both rounds 1 and 2), individuals were plastic in their behavior (i.e. inconsistent between rounds 1 and 2). After 16 weeks of hatchery rearing, neither growth nor survival were predicted by behavior. It is suggested that the behavioral plasticity within individuals through time makes consistent selection for strong feeders less likely, and that species with more plastic behavior may be less susceptible to unintentional selection on behavioral syndromes than species with behavior that is more fixed.     

Post‐release growth and dispersal of pond and hatchery‐reared European grayling Thymallus thymallus compared with their wild conspecifics in a small stream

The growth, and dispersal of stocked European grayling Thymallus thymallus, reared in a hatchery (fed dry food pellets) or in a pond (fed natural food), compared with their wild conspecifics was assessed from the recapture of individually tagged fish 168 days after their release into the Blanice River, Czech Republic. Recapture rates and site fidelity were higher for wild T. thymallus than for artificially reared fish. Specific growth rate and upstream or downstream dispersal did not significantly differ between any of the groups of fish. An influence of rearing conditions (pond v. hatchery) on the overall performance of stocked fish was not demonstrated. Initially, lower condition factors of reared T. thymallus were equal to wild fish after recapture, suggesting adaptation of artificially reared fish that remained in the sections studied.     

Wood addition in the hatchery and river environments affects post‐release performance of overwintering brown trout

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Behavioural Interactions and Hormones in Naturally and Hatchery‐Spawned Chinook Salmon

Artificial breeding programmes commonly lead to domestication, which is associated with many behavioural differences that can reduce the success of animals released into natural environments. To better understand the factors contributing to domestication, we used a captive population of Chinook salmon (Oncorhynchus tshawytscha) to partition hormonal and behavioural differences to effects of the breeding method and rearing environment. We compared 9‐mo‐old juveniles from three lines that shared a common genetic background: (1) the Channel line produced by natural spawning and reared in a low‐density environment with a natural substrate for approx. 6 mo before being transferred to the hatchery; (2) the Hatchery line produced by artificial spawning; and (3) the Transfer line produced by natural spawning but reared in the hatchery from the eyed‐egg stage. Plasma concentrations of 11‐ketotestosterone (11‐KT) and cortisol were measured in groups of 150 fish and again after 4 d of social interactions in groups of six fish. There was no difference in 11‐KT among lines in large groups, but in small groups, Transfer fish had lower 11‐KT concentrations and were significantly less aggressive than both Channel and Hatchery fish. Regardless of group size, concentrations of the stress hormone cortisol were nearly twofold higher in Channel fish than in Hatchery and Transfer fish. Furthermore, the elevated cortisol concentrations in Channel fish were associated with 35% lower feeding rates than in the other two lines. Our study details complex behavioural and hormonal responses to breeding method and rearing environment in juvenile salmon.     

The genetic structure of endangered indigenous populations of the amago salmon, <Emphasis Type="Italic">Oncorhynchus</Emphasis><Emphasis Type="Italic">masou</Emphasis><Emphasis Type="Italic">ishikawae</Emphasis>, in Japan

The amago salmon, Oncorhynchus masou ishikawae, is an endemic subspecies of O. masou in Japan. Owing to the extensive stocking of hatchery fish throughout Japan, indigenous populations of O. m. ishikawae are now on the verge of extinction. We examined the genetic effects of stocking hatchery fish on wild populations in the River Koza, Japan, using microsatellite and mitochondrial DNA (mtDNA) markers. For mtDNA, haplotype mt1, which is common in wild populations, was present exclusively in isolated wild populations assumed to be unaffected by previous stocking, while it was never observed in hatchery fish. Genetic diversity was much higher in wild populations in the stocked area, which shared many mtDNA haplotypes with hatchery fish, than in isolated wild populations with haplotype mt1. Pairwise F _ST estimates based on microsatellites showed significant differentiation among the isolated populations with many microsatellite loci monomorphic. Significant deviation from Hardy–Weinberg equilibrium was observed in wild populations in the area subject to stocking, where a Bayesian-based assignment test showed a high level of introgression with hatchery fish. These results suggest that wild populations with haplotype mt1, which became isolated through anthropogenic environmental change in the 1950–1960s, represent indigenous populations of O. m. ishikawae in the River Koza. They have low genetic diversity, most likely caused by genetic bottlenecks following damming and environmental deterioration, while stocking of hatchery fish over the past 30 years apparently had a large impact on the genetic structure of wild populations in the main channel of the River Koza.     

Experimental evidence of population-specific marine spatial distributions of Chinook salmon, <Emphasis Type="Italic">Oncorhynchus tshawytscha</Emphasis>

Migratory behavior can be affected by attributes of the animals themselves such as size and growth rate, external factors such as biotic and abiotic features of the environment, and also genetic tendencies. To better understand the role of genetics in the migratory behavior of Chinook salmon, Oncorhynchus tshawytscha, we report the results of an experiment in which two populations (University of Washington (UW) hatchery and Elwha River) and their hybrid offspring were reared at, tagged, and released from a single site, the UW hatchery, at a common size and date. The patterns of recoveries in fisheries differed markedly with respect to spatial distribution and also age of the fish. A larger proportion of the Elwha River fish were recovered in Puget Sound in their first year of marine life than the other groups (40.7% vs. 11.2% for UW and 7.0% for the hybrids). The Elwha River fish also showed a higher proportion of northerly recoveries (21.9%) than UW fish (1.7%), and hybrids showed an intermediate value (8.1%). In contrast, no Elwha River fish were recovered south along the Washington coast compared to 1.3% of the hybrids and 7.7% of the UW fish. The specific mechanisms controlling the migration patterns of the populations remain unclear but the results strongly indicated a genetic influence on distribution patterns.     

Frog breeding pond selection in response to predators and conspecific cues

Predators are a major influence on the breeding site selection decisions of anurans. Many species actively avoid breeding in habitat with predators when given the choice between predator and predator‐free sites. However, certain factors such as site fidelity or conflicting cues may preclude avoidance behavior. We conducted two experiments examining how western chorus frogs, Pseudacris triseriata, respond to predators, western mosquitofish, Gambusia affinis, using an array of artificial ponds located at two field sites. In one experiment, we added G. affinis to half of our experimental ponds and monitored subsequent colonization by frogs. We found that frogs laid significantly fewer eggs in ponds with fish compared to fishless ponds. In another experiment, we introduced an additional cue to complicate the decision‐making process and monitored colonization of ponds in response to treatments of conspecific breeding cues only (eggs), predators (G. affinis) only, and conspecific cues and predators. We found no significant differences in number of eggs deposited among these three treatments. Based on these results, P. triseriata does not always exhibit complete avoidance of fish predators, and avoidance may vary based on factors such as site fidelity or dispersal costs. This study represents a step toward understanding how multiple biotic factors at a breeding pond may influence anuran site selection behavior in the field.     

Habitat characteristics of juvenile cowcod, <Emphasis Type="Italic">Sebastes levis</Emphasis> (Scorpaenidae), in Southern California

We characterized habitat requirements of juvenile cowcod, Sebastes levis, using information from surveys conducted aboard the manned research submersible Delta. We conducted 303 dive surveys on rocky banks and outcrops in water depths between 28 and 365 m in southern and central California, covering 483 km (963,940 m²) of seafloor. We counted 549,263 fishes from at least 134 species; 216 individuals were juvenile cowcod, S. levis, of 45 cm or less in total length (TL). Juvenile cowcod occupied depths between 52 and 330 m and demonstrated ontogenetic shifts in their habitat associations. Small fish (5–20 cm TL) lived primarily among cobbles or cobbles and small boulders. As fish grew, they moved into high-relief rock habitats, including boulder fields and rock ridges. Small cowcods were found with pygmy, Sebastes wilsoni, and swordspine, Sebastes ensifer, rockfishes. Larger juveniles often associated with juvenile bocaccio, Sebastes paucispinis, juvenile widow rockfish, Sebastes entomelas, and squarespot rockfish, Sebastes hopkinsi. Our study resulted in a characterization of seafloor habitats on a small spatial scale that is relevant to juvenile cowcod nursery areas, which is important when considering effective management strategies for this overfished species.     

Role of olfaction and vision in homing behaviour of black rockfish Sebastes inermis

How fish find their original habitat and natal home remains an unsolved riddle of animal behaviour. Despite extensive efforts to study the homing behaviour of diadromous fish, relatively little attention has been paid to that of non-diadromous marine fish. Among these, most rockfish of the genus Sebastes exhibit homing ability and/or a strong fidelity to their habitats. However, how these rockfish detect the homeward direction has not been clarified. The goal of the present research was to investigate the sensory mechanisms involved in the homing behaviour of the black rockfish Sebastes inermis, using acoustic telemetry. Vision-blocked or olfactory-ablated rockfish were released in natural waters and their homing behaviours compared with those of intact or control individuals. Blind rockfish showed homing from both inside and outside their habitat. The time taken by blind fish to reach their home habitat was not significantly different from that of the control fish. In contrast, most olfactory-ablated fish did not successfully reach their original habitat. Our results indicate that black rockfish predominantly use the olfactory sense in their homing behaviour.     

Migration characteristics of hatchery and natural-origin <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis> from the lower Mokelumne River,California

The lower Mokelumne River (LMR), located in the California Central Valley, supports a population of natural-origin Oncorhynchus mykiss. In addition, the Mokelumne River Fish Hatchery (Hatchery) contributes hatchery produced O. mykiss to the system annually. We conducted a 3 year acoustic tagging study to evaluate the migratory characteristics of LMR hatchery and natural-origin O. mykiss to the Pacific Ocean. Specifically, we analyzed downstream movement and migration rates, routes, and success of acoustically tagged O. mykiss of hatchery and natural origin under variable release locations in non-tidal and tidal habitats. Results from our study suggest there are significant differences in the proportion of hatchery and natural O. mykiss that demonstrate downstream movement. Fish origin, size, and release location all had a significant effect on whether an individual demonstrated downstream movement. Mokelumne origin O. mykiss that initiated downstream movement utilized numerous migration routes throughout the Delta during their migration towards the Pacific Ocean. We identified four primary migration pathways from the lower Mokelumne River through the Sacramento-San Joaquin Delta while the Delta Cross Channel was closed. However, several other pathways were utilized. Origin had a significant effect on O. mykiss success in reaching key points in the Delta and through the Estuary. Fish size had a significant effect on whether an individual reached the marine environment. Of the 467 O. mykiss tagged, 34 successfully reached the Pacific Ocean (Golden Gate Bridge), and of these, 33 were hatchery-origin and 1 was natural-origin. A higher proportion of hatchery-origin fish (10% of tagged) migrated to the ocean compared to natural-origin fish (<1%). Our study provides valuable information on the differences between hatchery and natural-origin O. mykiss migration characteristics as well as unique insight into the migratory behavior of little studied non-Sacramento River origin salmonids.     

Effects of habitat enrichment and food availability on the foraging behaviour of juvenile Atlantic Cod (<Emphasis Type="Italic">Gadus morhua L</Emphasis>)

The environment can play an important role in shaping how an animal behaves, and how well the animal performs in a particular environment can be influenced by early experiences. The tradition of releasing captive-reared juveniles into the wild in an effort to strengthen wild fish populations has often had little success owing to high post-release mortality. Fish reared under standard hatchery conditions are provided with fewer stimuli and they receive excess quantities of pellet food that are easy to handle and consume. Captive reared fish therefore appear to be under-stimulated and overfed. Several studies have demonstrated that simple structural enrichment in the rearing facilities promotes flexible behaviour compared to fish reared in plain, standard hatchery tanks. Less attention has been given to the effects of the diet. Here we use a cross-factored design to test the relative role of food ration and spatial enrichment on foraging behaviour. Our results show that fish from enriched environments, regardless of previous food-ration size, were more reluctant to start feeding on the first day in a novel arena. On day two and three, however, fish with prior experience of a low food ration showed greater foraging activity and efficiency than fish fed on full rations. On the second and third day, prior experience with enrichment was less important. We discuss how early feeding experience in combination with structural enrichment may contribute in producing fish that are better suited for release into the wild.     

Rearing and migration of juvenile Chinook salmon (<Emphasis Type="Italic">Oncorhynchus tshawytscha</Emphasis>) in a large river floodplain

Off-channel habitat has become increasingly recognized as key for migratory fishes such as juvenile Chinook salmon (Oncorhynchus tshawytscha). Hence, floodplain habitat has been identified as critical for the continued persistence of California’s Central Valley salmon, particularly the Yolo Bypass, the primary floodplain of the Sacramento River. To provide insight into factors supporting juvenile salmon use of this 240 km², partially leveed floodplain, we examined inter- and intra-annual relationships between environmental correlates and residency time, apparent growth, emigration, migratory phenotype, and survival over more than a decade for natural-origin (“wild”) fish and experimentally-released hatchery fish. Flood duration was positively associated with hatchery juveniles residing longer and achieving larger size. Wild juveniles grew larger and emigrated later with cumulative temperature experience (accumulated thermal units) and warmer average annual temperatures during flood years. Within years, both wild and hatchery salmon departed the floodplain as flood waters receded. Parr-sized juveniles dominated outmigrant composition, though fry and smolt-sized juveniles were also consistently observed. Survival to the ocean fishery was not significantly different between hatchery fish that reared in the Yolo Bypass versus those that reared in the main stem Sacramento River. Our study indicates improved frequency and duration of connectivity between the Sacramento River and the Yolo Bypass could increase off-channel rearing opportunities that expand the life history diversity portfolio for Central Valley Chinook salmon.     

Distribution, Habitat, and Behavior of Rockfishes, Sebastes spp., in Nearshore Waters of Southeastern Alaska: Observations From a Remotely Operated Vehicle

We examined distribution, habitat, and behavior of rockfishes, Sebastes spp., with a remotely operated vehicle (ROV) in coastal waters <90m deep of southeastern Alaska from 1998 to 2000. We identified black, S. melanops, canary, S. pinniger, China, S. nebulosus, copper, S. caurinus, dusky, S. ciliatus, harlequin, S. variegatus, Puget Sound, S. emphaeus, quillback, S. maliger, redstripe, S. proriger, rosethorn, S. helvomaculatus, silvergray, S. brevispinis, tiger, S. nigrocinctus, yelloweye, S. ruberrimus, and yellowtail, S. flavidus, rockfish. Quillback and dusky rockfish were the most widely distributed species, China and harlequin rockfish were the least widely distributed species. Species richness was greater at sites on or near the outer coast than at sites in more inside, sheltered waters. Most (>75%) observations of rockfish were over complex bottoms of boulder and rock or in vertical bedrock wall habitats. Few rockfish were observed over soft bottoms with no relief. Median depth of observation was 30m for black, copper, dusky, and yellowtail rockfish and >30m for all other species. Median temperature of observation ranged from 6.1°C for harlequin rockfish to 9.4°C for black rockfish. Size of fish was positively correlated (p 0.036) with depth for dusky, quillback, and yelloweye rockfish. Species often observed alone were China (67%), copper (46%), quillback (46%), and rosethorn (43%) rockfish. Most (70%) observations of harlequin, Puget Sound, silvergray, tiger, and yelloweye rockfish were in mixed species assemblages. When first observed, the behavior of most rockfish species was swimming or hovering. Notable exceptions were China, harlequin, rosethorn, and tiger rockfish; 33–57% were resting on bottom or in a hole or crevice.     

Do stocked hatchery‐reared juveniles ecologically suppress wild juveniles in Salvelinus leucomaenis?

The dominancy of semi‐wild and hatchery‐reared white‐spotted charr Salvelinus leucomaenis juveniles was evaluated using pair‐wise enclosure tests and field stocking tests. The semi‐wild S. leucomaenis originated in a hatchery, being stocked into the test stream as eyed‐eggs. In the pair‐wise enclosure test, the semi‐wild S. leucomaenis dominated the hatchery S. leucomaenis that were of a similar standard length (L_S). The semi‐wild S. leucomaenis were subordinate to hatchery S. leucomaenis that were > 11% larger in L_S. In the field stocking test, the abundance and growth of semi‐wild S. leucomaenis was decreased in the presence of larger hatchery S. leucomaenis (14% larger L_S). Taken together, these results suggest that larger hatchery S. leucomaenis ecologically suppress the smaller semi‐wild S. leucomaenis. Salvelinus leucomaenis juveniles that are stocked with the intention of supplementing natural populations should be < 10% larger than their wild counterparts at the time of stocking to minimize their competitive advantage. The semi‐wild and hatchery S. leucomaenis used in both tests were genetically similar individuals, suggesting that the differences are due to the early rearing environment of either a natural stream or hatchery. The hatchery S. leucomaenis have lower levels of aggression as a result of selection in the hatchery rearing environment. Rearing in a natural stream from the eyed‐egg stage is likely to increase their lowered aggression.     

Migratory patterns of lower Feather River natural and hatchery-origin Oncorhynchus mykiss

Oncorhynchus mykiss are known to exhibit variable life histories expressed under genetic control or through the influence of the environment. Altered environmental conditions and the presence of large numbers of non-indigenous hatchery fish can affect the rate of anadromy observed in California’s Central Valley O. mykiss. The lower Feather River, a large regulated river in Northern California, supports one of the largest populations of O. mykiss in the Central Valley, heavily subsidized by hatchery production. I examined downstream migratory behavior, movement rate, and success of natural-origin juveniles, natural-origin adults, and hatchery-origin fish using acoustic telemetry. I found that all three groups displayed a mix of migratory and non-migratory life histories. Hatchery-origin adults exhibited more migratory behavior (anadromy) than natural-origin juveniles and natural-origin adults, 41 %, 24 %, and 13 % respectively. Downstream migrants were also significantly larger than non-migratory fish. Migration timing was similar among the three groups, but natural-origin juveniles displayed the most rapid rate of movement. The relative success of each group was highest for fish migrating through the Sacramento-San Joaquin Delta to the Pacific Ocean. Hatchery-origin adults migrating through the lower Feather River showed the lowest relative success (33 %). The dominance of non-migratory life histories pattern among lower Feather River O. mykiss may be in response to the suitable habitat provided by hypolimnetic releases below dams and the current hydrological regime within the highly altered Sacramento-San Joaquin watershed.     

Short-Term Fidelity,Habitat Use and Vertical Movement Behavior of the Black Rockfish Sebastes schlegelii as Determined by Acoustic Telemetry

The recent miniaturization of acoustic tracking devices has allowed fishery managers and scientists to collect spatial and temporal data for sustainable fishery management. The spatial and temporal dimensions of fish behavior (movement and/or vertical migrations) are particularly relevant for rockfishes (Sebastes spp.) because most rockfish species are long-lived and have high site fidelity, increasing their vulnerability to overexploitation. In this study, we describe the short-term (with a tracking period of up to 46 d) spatial behavior, as determined by acoustic tracking, of the black rockfish Sebastes schlegelii, a species subject to overexploitation in the Yellow Sea of China. The average residence index (the ratio of detected days to the total period from release to the last detection) in the study area was 0.92 ± 0.13, and most of the tagged fish were detected by only one region of the acoustic receiver array, suggesting relatively high site fidelity to the study area. Acoustic tracking also suggested that this species is more frequently detected during the day than at night in our study area. However, the diel detection periodicity (24 h) was only evident for certain periods of the tracking time, as revealed by a continuous wavelet transform. The habitat selection index of tagged S. schlegelii suggested that S. schlegelii preferred natural reefs, mixed sand/artificial reef bottoms and mixed bottoms of boulder, cobble, gravel and artificial reefs. The preference of this species for the artificial reefs that were recently deployed in the study area suggests that artificial seascapes may be effective management tools to attract individuals. The vertical movement of tagged S. schlegelii was mostly characterized by bottom dwelling behavior, and there was high individual variability in the vertical migration pattern. Our results have important implications for S. schlegelii catchability, the implementation of marine protected areas, and the identification of key species habitats, and our study provides novel information for future studies on the sustainability of this important marine resource in eastern China.     

Ontogenetic and sex‐based differences in habitat preferences and site fidelity of White's seahorse Hippocampus whitei

The aim of this study was to determine and compare habitat preferences for male and female adult and juvenile White's seahorse Hippocampus whitei and assess their movements and site fidelity over 4 years. Data were collected from three sites along 1·5 km of estuarine shoreline in Port Stephens, New South Wales, Australia, from 2006 to 2009 using H. whitei that had been tagged with visible implant fluorescent elastomer. Relative availability of 12 habitats and habitat preferences of H. whitei was determined, based on the habitat that H. whitei used as a holdfast. Hippocampus whitei occurred in nine different habitats; adults preferred sponge and soft coral Dendronephthya australis habitats with no difference between male and female habitat preferences whilst juveniles preferred gorgonian Euplexaura sp. habitat. There was a significant preference by adults for D. australis colonies with height >40 cm and avoidance of colonies <20 cm. Neither adults nor juveniles used sand or the seagrasses Zostera muelleri subsp. capricorni and Halophila ovalis. Hippocampus whitei showed cryptic behaviour with c. 50% of adult sightings cryptic and c. 75% for juveniles with crypsis occurring predominantly in Sargassum sp. for adults and Euplexaura sp. habitat for juveniles. Within sites, females moved significantly longer distances (maximum of 70 m) than males (maximum of 38 m) over 20 months. Strong site fidelity was displayed by H. whitei with males persisting at the same site for up to 56 months and females for 49 months and no H. whitei moved between sites. The longest period that an H. whitei was recorded on the same holdfast was 17 months for a male and 10 months for a female. As this species displays strong site fidelity, specific habitat preferences and has a limited distribution, future management needs to minimize the risk of habitat disturbance as loss of key habitats could have a negative effect on species abundance and distribution.     

Juvenile sparids (Rhabdosargus holubi) consistently select structurally dense vegetated habitat in nursery seascapes

Seagrass habitats provide structural complexity in coastal estuarine and marine environments, which offer fish optimal foraging grounds and refuge from predation. However, seagrasses are some of the most threatened ecosystems globally, with anthropogenic activities such as population growth and environmental degradation leading to the fragmentation, thinning, and loss of these habitats. Rhabdosargus holubi is one of only a few vegetation-associated marine fish species in South African estuaries. Although field studies have shown a strong association with seagrass over other aquatic vegetation for the juveniles of this species, habitat choice has never been empirically tested. Here, we used artificial vegetation units to test habitat choice (different structural complexities) for this species. We also tested whether habitat choice is influenced by a predatory threat, with fish preferentially selecting dense habitat in the presence of a predator and whether this effect may be more apparent in smaller individuals. We found that R. holubi significantly prefer greater structural complexity over less complex habitats, in both the absence and presence of a predator and for both small and large juveniles, showing that R. holubi actively choose more complex structures and are attracted to the structure per se irrespective of the threat of predation. This study highlights the importance of dense seagrass as nursery areas for this species and demonstrates how the loss of these habitats could impact the nursery function of estuaries.     

To clean or not to clean: Cleaning mutualism breakdown in a tidal environment

The dynamics and prevalence of mutualistic interactions, which are responsible for the maintenance and structuring of all ecological communities, are vulnerable to changes in abiotic and biotic environmental conditions. Mutualistic outcomes can quickly shift from cooperation to conflict, but it unclear how resilient and stable mutualistic outcomes are to more variable conditions. Tidally controlled coral atoll lagoons that experience extreme diurnal environmental shifts thus provide a model from which to test plasticity in mutualistic behavior of dedicated (formerly obligate) cleaner fish, which acquire all their food resources through client interactions. Here, we investigated cleaning patterns of a model cleaner fish species, the bluestreak wrasse (Labroides dimidiatus), in an isolated tidal lagoon on the Great Barrier Reef. Under tidally restricted conditions, uniquely both adults and juveniles were part‐time facultative cleaners, pecking on Isopora palifera coral. The mutualism was not completely abandoned, with adults also wandering across the reef in search of clients, rather than waiting at fixed site cleaning stations, a behavior not yet observed at any other reef. Contrary to well‐established patterns for this cleaner, juveniles appeared to exploit the system, by biting (“cheating”) their clients more frequently than adults. We show for the first time, that within this variable tidal environment, where mutualistic cleaning might not represent a stable food source, the prevalence and dynamics of this mutualism may be breaking down (through increased cheating and partial abandonment). Environmental variability could thus reduce the pervasiveness of mutualisms within our ecosystems, ultimately reducing the stability of the system.     

Factors that contribute to the ecological risks of salmon and steelhead hatchery programs and some mitigating strategies

State and federal agencies in the United States annually release millions of hatchery salmon and steelhead into public waters. Many of the hatchery programs are located in areas where the wild populations are now listed under the U.S. Endangered Species Act (ESA) (16 U.S.C. §§ 1531–1544). These hatchery programs pose genetic and ecological risks to wild fish populations. Genetic risks occur when hatchery and wild fish interbreed and usually occur within a taxonomic species. Ecological risks occur when the presence of hatchery fish affects how wild fish interact with their environment or with other species and may affect whole species assemblages. This paper reviews some of the factors that contribute to ecological risks. Important contributing factors include the relative abundance of hatchery and wild fish in natural production areas, hatchery programs that increase density-dependant mortality, residual hatchery fish, some physical advantages that hatchery fish can have over wild fish, and life history characteristics that may make some species especially vulnerable to the effects of ecological risks. Many of these risk factors can be mitigated by management activities that reduce the level of interactions between hatchery and wild fish. This paper concludes by recommending twelve mitigation strategies that may be useful when agencies need to bring hatchery programs into compliance with the take provisions of the ESA.