Use of pelagic prey subsidies by demersal predators in rocky reefs: insight from movement patterns of lingcod

Allochthonous subsidies of energy and nutrients can affect community structure in patchy marine habitats, including rocky reefs, and their ecological consequences may depend on the mechanism of energy transfer. Lingcod (Ophiodon elongatus) are demersal predators that trophically link nearshore rocky reefs with offshore pelagic habitats through consumption of pelagic fishes. We quantified lingcod habitat use and movement patterns to make inferences about the temporal and spatial conditions under which lingcod may acquire pelagic prey. Lingcod maintained small home ranges (21,272 ± 13,630 m²) within a rocky reef in the San Juan Archipelago, Washington; eight of nine individuals used rocky habitat exclusively. Depths occupied by lingcod (0–50 m) coincided with pelagic fish distribution on the rocky reef; however, diel patterns in lingcod activity varied inversely with occurrence of pelagic fishes on the reef. Our findings suggest that the pelagic subsidy to lingcod is not strongly mediated through directed off-reef foraging by lingcod.     

Home range and habitat utilization of adult California sheephead,<Emphasis Type="Italic"> Semicossyphus pulcher</Emphasis> (Labridae), in a temperate no-take marine reserve

The California sheephead, Semicossyphus pulcher Ayres (Labridae), is a carnivorous, temperate, rocky-reef/kelp-bed species that is highly sought in recreational and commercial fisheries. Fine-scale acoustic telemetry tracking was used to ascertain the home range and habitat utilization of S. pulcher. Sixteen adult S. pulcher (26–38 cm SL) were surgically fitted with small acoustic transmitters and manually tracked for up to 144 h during multiple, 24-h periods between March 2001 and August 2002 within the Catalina Marine Science Center Marine Life Reserve (33°26N; 118°29W). A geographic information system was used to calculate home range sizes (95% kernel utilization distributions) and habitat use. Tracking of the first five fish over 24 h confirmed that S. pulcher were strictly diurnal, so the remaining 11 fish were tracked from 1 h before sunrise to 1 h after sunset. Home ranges varied greatly, from 938 to 82,070 m², with a mean (±SD) of 15,134±26,007 m². Variability in home range sizes among fish was attributed to differences in habitat shape (embayment vs. contiguous coastline) and to natural habitat boundaries (deep, sandy expanses) in adjacent areas within the reserve. There was a significant relationship between fish length and proportion of time spent in different habitats (sand vs. reef). S. pulcher were found within rocky-reef areas 54% of the time, and, within these areas, a greater percentage of daytime was spent in high-relief areas. Based on the relatively small size and persistence of home ranges of adult S. pulcher, no-take reserves, if they contain appropriate habitat, would provide adequate protection for their stocks.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00227-005-1573-1.Communicated by J.P. Grassle, New Brunswick     

Photographic and acoustic tracking observations of the behaviour of the grenadier Coryphaenoides (Nematonurus) armatus the eel Synaphobranchus bathybius,and other abyssal demersal fish in the North Atlantic Ocean

Using an autonomous free-fall vehicle (AU-DOS), observations were made of demersal fish attracted to baits and baited acoustic transmitters at two stations in the North Atlantic Ocean. A comparison was made between Station PAP (48°50N; 16°30W), 4800 m deep on the Porcupine Abyssal Plain which is relatively eutrophic, and Station MAP (31°N; 20°W), 4900 m deep on the Madeira Abyssal Plain, which is oligotrophic. Experiments were conducted during summer, in 1989 and 1990. Four species of fish were observed at Station MAP, the grenadier, Coryphaenoides (Nematonurus) armatus, the eel, Synaphobranchus bathybius, and the ophidiids Spectrunculus grandis, and Barathrites sp. At Station PAP, C. (N.) armatus and H. (S.) bathybius were attracted to bait on all deployments and only two other individuals of different species, probably ophidiids, were seen. The mean first grenadier arrival time was 30 and 138 min at Stations PAP and MAP, respectively. Mean first eel arrival time was 29 and 151 min at Stations PAP and MAP, respectively. Estimated population densities of fish were 167 grenadiers km^-2 and 180 synaphobranchid eels km^-2 at Station PAP and 8 grenadiers km^-2 and 7 eels km^-2 at Station MAP. Only the grenadier C. (N.) armatus definitely ingested transmitters, and this species dominated fish activity around the baits. Mean time of departure of grenadiers with transmitters in their stomachs across an acoustic horizon at 1000 m range was 371 and 488 min at Stations PAP and MAP, respectively. Grenadiers had a longer mean staying time at the food source at the more oligotrophic Station MAP (364 min) than at Station PAP (141 min). This corresponds with predictions of optimal foraging theory.     

Variation in plasma levels of insulin-like growth factor-I (IGF-I) in lingcod: relationships among season,size, and gonadal steroids

The physiological response of a fish to its environment is mediated through the endocrine axis controlling growth. Therefore, growth-regulating hormone levels can serve as ecologically relevant indicators of fish growth rate. We quantified variation in plasma insulin-like growth factor-I (IGF-I) to evaluate its potential as an indicator of growth in lingcod, an economically and ecologically important bottomfish species in the northeast Pacific. An information-theoretic model selection approach was used to test the hypothesis that variation in lingcod IGF-I is related to season, body size, and gonadal steroid concentration. Season and a length × season interaction were the most important predictors of plasma IGF-I among the variables we evaluated, suggesting that season and body size should be explicitly accounted for when interpreting endocrine patterns in wild fish populations. This is among the few studies that have measured and interpreted patterns of IGF-I in wild fish and the first to describe seasonal endocrine profiles in lingcod.     

Spatial ecology and residency patterns of adult great barracuda (<Emphasis Type="Italic">Sphyraena barracuda</Emphasis>) in coastal waters of The Bahamas

Great barracuda (Sphyraena barracuda) were implanted with acoustic telemetry transmitters (n = 42) and monitored within a stationary acoustic receiver array (n = 53 receivers) in The Bahamas to examine residency, seasonal movements, and habitat use. Barracuda were monitored for up to 980 days and remained within the array area ~33% (median value) of the time. Most tagged barracuda were transient and would often disappear from the array for months at a time, particularly in the summer where they were usually last detected on receivers located in deeper shelf habitats, and then return at other times in the year. Habitat use across the footprint of the array differed, with most detections occurring in coastal areas and comparatively fewer in deeper mosaic or shelf habitats. Linear home range estimates revealed that some barracuda moved >12 km within a single day and are capable of migrating >100 km to other islands in the Bahamian Archipelago. Our results provide some of the first telemetry data for this apex marine predatory fish and the first reliable information on the residency and localized seasonal movements of adult great barracuda in the coastal waters of the Western Atlantic.     

Satellite tracking of Humboldt penguins (Spheniscus humboldti) in northern Chile

During the El Niño of 1982/1983, the Humboldt penguin population diminished dramatically in the whole distributional area of the species. Recovery of the population was slow since 1983 and it has been suggested that large numbers of Humboldt penguins die at sea, entangled in nets, or starve to death, even during non-“El Niño” years. We were able to determine for the first time, how Humboldt penguins on Pan de Azúcar Island (26°S; 72°W) utilize their marine habitat and where their feeding areas lie. For this purpose we employed two streamlined Argos satellite transmitters during the 1994/1995 and 1995/1996 breeding seasons, respectively. Mean travelling speed of Humboldt penguins during foraging trips was 0.94?m s^?1 and 50% of bird positions were located within 5?km of the island (90% within 35?km). Total area covered by Humboldt penguins foraging from Pan de Azúcar Island was 12?255?km². Satellite transmitters also recorded dive duration; penguins spent on average 7.8 to 9?h diving per foraging day but showed no preferences for particular feeding areas. Mean daily dive durations (4-d mean) recorded during the 1994/1995 breeding season were positively correlated between birds. Significant correlation between dive duration and sea surface temperature anomalies and negative correlation between dive duration and fishery landings at nearby Caldera harbour indicate that the 1994/1995 increase in foraging effort was a response to deteriorating prey availability. Sea surface temperatures during the 1995/1996 breeding season were colder than average, and we observed no trends in bird diving activities.     

Incorporation of organic aggregates by marine mussels

Two marine mussels, Geukensia demissa (Dillwyn) and Mytilus edulis (L.) collected in 1990 in Old Silver Beach, Falmouth, Massachusetts, incorporated nitrogen when fed ¹⁵N-labelled organic aggregates produced from dissolved organic nitrogen released by the brown sea-weed Fucus vesiculosis. Uptake of ¹⁵N on the aggregate diet was linear over the course of 24 h, and unincorporated ¹⁵N was eliminated from the gut after 48 h. Both species of mussels incorporated approximately five times more N when they were fed organic aggregates than when they were fed either ¹⁵N-labelled dissolved organic material (DOM) or particulate detritus, both of which were also derived from the seaweed. Nitrogen uptake was greatest in controls fed the diatom Thalassiosira weissflogii; mussels fed phytoplankton incorporated seven times more nitrogen than those fed aggregates. However, aggregates could supply an estimated 7 to 14% of the N requirements for both mussels, whereas DOM or particulate detritus could only supply 1 to 3%. These data provide evidence that a food web pathway exists from primary producer to released dissolved organic nitrogen to microbial organic aggregate to metazoan consumer, and, further, that it can be more important in a detrital food web than either particulate detritus or DOM.     

Combined Effects of Levels of Protection and Environmental Variables at Different Spatial Resolutions on Fish Assemblages in a Marine Protected Area

Abstract: The links between species–environment relations and species’ responses to protection are unclear, but the objectives of marine protected areas (MPAs) are most likely to be achieved when those relations are known and inform MPA design. The components of a species’ habitat vary with the spatial resolution of the area considered. We characterized areas at two resolutions: 250 m² (transect) and approximately 30,000 m² (seascape). We considered three categories of environmental variables: substrate type, bottom complexity, and depth. We sought to determine at which resolution habitat characteristics were a better predictor of abundance and species composition of fishes and whether the relations with environmental variables at either resolution affected species’ responses to protection. Habitat features accounted for a larger proportion of spatial variation in species composition and abundances than differences in protection status. This spatial variation was explained best by habitat characteristics at the seascape level than at the transect level. Species’ responses to protected areas were specific to particular seascape characteristics, primarily depth, and bottom complexity. Our method may be useful for prioritizing marine areas for protection, designing MPAs, and monitoring their effectiveness. It identified areas that provided natural shelter, areas acting as buffer zones, and areas where fish species were most responsive to protection. The identification of such areas is necessary for cost‐effective establishment and monitoring of MPAs.     

Transmitter attachment and release methods for short-term shark and stingray tracking on coral reefs

This study details a simple and cost-effective means of attaching acoustic transmitters to coral reef sharks and stingrays, which potentially allows for retrieval and reuse on completion of tracks. Between 2008 and 2011, galvanised timed releases were trialled in both static field tests and on blacktip reef sharks Carcharhinus melanopterus, cowtail Pastinachus atrus, and porcupine Urogymnus asperrimus rays in Coral Bay (?23°08′41″, 113°45′53″), Western Australia. The timed releases remained attached to animals for the duration required for tracking and in four out of five deployments transmitters were recovered after release from the animals. The use of modified Rototags for sharks and stainless steel darts for stingrays allowed rapid and effective attachment to animals, with limited impact on their welfare in the short term. External attachment for short-term tracking of coral reef-associated elasmobranchs should be considered as a complementary option to internal placement of transmitters in animals either by surgery or by ingestion.     

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.     

Home range, activity and distribution patterns of a temperate rocky-reef fish, Cheilodactylus fuscus

Red morwong (Cheilodactylus fuscus; Cheilodactylidae: Perciformes), are large temperate rocky reef fish that are patchily distributed in local aggregations of 3 to >100 fish. The home ranges and aggregating behaviour of red morwong were investigated using external tags (n = 114, over 35 mo) and ultrasonic transmitters (n = 9 over 20 d) at coastal and estuarine sites in south-east Australia. Adult red morwong had a mean home range during the day of 1865 m² (SE = 268). Night movement, determined by ultrasonic telemetry, indicated a significantly greater mean home range of 3639 m² (SE = 416). Home range did not differ significantly with size or sex. Fish movements were greatest and aggregation sizes varied most during the non-reproductive mid-summer period. Tagged fish (N = 20) displaced 200 to 900 m returned in 1 to 3 d to the point of capture, often traversing open sand habitat and other aggregations. During the day, fish were commonly found on bouldered habitat. During the night, these site-specific aggregations fragmented as fish dispersed over a variety of substrata, with crepuscular peaks in activity. Therefore, estimates of habitat-specificity and feeding patterns collected only by day may give misleading results. Received: 28 June 1996 / Accepted: 8 July 1998     

Trophic strategies of garfish, Arrhamphus sclerolepis, in natural coastal wetlands and artificial urban waterways

We used carbon stable isotope and stomach content analyses to test whether snub-nosed garfish, Arrhamphus sclerolepis (Hemiramphidae), in the extensive artificial urban waterways of southeast Queensland, Australia, rely on autotrophic sources different to those in natural wetlands. Carbon isotope values of A. sclerolepis were similar to those in previous investigations, with enriched values in natural habitat (mean = −13.9‰, SE=0.6) and depleted values (−19.1‰, 0.1) in artificial habitat. A. sclerolepis in natural habitat consumed large amounts of seagrass during the day and night, and at night also ingested small quantities of crustacean prey. In artificial habitat, A. sclerolepis consumed macroalgae during the night and switched to invertebrates (terrestrial ants) in the day. Values of δ¹⁵ N in all the fish were 3–8‰ more enriched than sources. Mathematical modelling of feasible source mixtures showed that in natural habitat the bulk of the dietary carbon is obtained from seagrass, but the nitrogen is obtained from animal prey. In artificial habitat, carbon is obtained from a mixture of macroalgae and animals. We could not determine the nitrogen sources in artificial habitat of A. sclerolepis since, even after accounting for trophic fractionation of δ¹⁵ N, the values were outside the range of potential sources. If the types of animals ingested vary over time, perhaps one or more types of animal important in the provision of nitrogen was not sampled during the study. This study demonstrates that not only does A. sclerolepis occur in both artificial and natural habitats, but it uses the same strategy of bulk herbivory with the inclusion of smaller amounts of animal prey. This understanding of how ecological processes support fisheries production in artificial habitat improves the overall understanding of the effects of urbanisation on coastal food webs.     

Activity,track and speed of movement of the crab Scylla serrata in an estuary

Ultrasonic transmitters were used to track the movements of the crab Scylla serrata (Forskal) over 24 h periods in the Kowie estuary, South Africa. Laboratory experiments using infra-red time-lapse photography to record activity indicated that the transmitters did not affect duration of emergence, amount of movement or feeding. In the estuary, S. serrata was active on average for 13 h. out of 24 h, most activity was at night. The distance moved per night by continuously tracked crabs averaged 461 m, but ranged between 219 and 910 m. Most movement was slow, modal speed was 10 to 19 m h^-1. Slow movements were independent of direction of current and are assumed to be related to use of contact chemoreception for location of prey. About one-seventh of movements were faster than 70 m h^-1; these were most frequently against the current and may be related to olfactory location of food. The crabs did not occupy a distinct territory, but tended to remain in the same general area although they were capable of moving at least 800 m along the length of the estuary at night.     

Ecological gradients and relative abundance of native (Mytilus trossulus) and invasive (Mytilus galloprovincialis) blue mussels in the California hybrid zone

Marine communities are experiencing unprecedented rates of species homogenization due to the increasing success of invasive species, but little is known about the mechanisms that allow a species to invade and persist in a new habitat. In central California, native (Mytilus trossulus Gould 1850) and invasive (Mytilus galloprovincialis Lamarck 1819) blue mussels and their hybrids co-exist, providing an opportunity to analyze the mechanisms that determine the distributions of these taxa. Spatial and temporal variation in temperature and salinity and the relative frequencies of these mussel taxa were examined between 2000 and 2004 at four sites in San Francisco Bay and four in Monterey Bay, which were chosen for their different positions along inferred estuarine/oceanic gradients in the hybrid zone. Mussels were genetically identified as the parent species or hybrids by amplifying regions of two species-specific loci: the adhesive byssal thread protein (Glu-5′) and the internal transcribed spacer region of ribosomal DNA (ITS 1). The proportion of M. trossulus at the eight hybrid zone sites correlated negatively with average salinity (R ²=0.60) and positively with maximal temperature (R ²≥0.72), a somewhat unexpected result given what is known about the phylogeography of this species. The proportion of M. galloprovincialis showed the opposite pattern. The proportion of hybrids was correlated neither with habitat temperature nor salinity. Genotypes of mussel populations at an additional 13 sites from Coos Bay, Oregon (latitude 43.35°N) to Long Beach, California (latitude 33.72°N), sampled at various intervals between 2000 and 2004, were also determined. This survey confirmed previous reports that the hybrid zone lies between Monterey and the Cape Mendocino region (latitudes 36.63°N–40.5°N). Within Monterey and San Francisco Bays, however, the temporal comparisons (1990s vs. 2000s) revealed abrupt changes in the proportions of the two parent species and their hybrids on annual and decadal time scales. These changes indicate that the blue mussel populations are in a highly dynamic state. The survey also showed that, regardless of habitat, M. trossulus is consistently of smaller average size than either M. galloprovincialis or hybrids.

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Contrasting ecological information content in whaling archives with modern cetacean surveys for conservation planning and identification of historical distribution changes

Many species are restricted to a marginal or suboptimal fraction of their historical range due to anthropogenic impacts, making it hard to interpret their ecological preferences from modern-day data alone. However, inferring past ecological states is limited by the availability of robust data and biases in historical archives, posing a challenge for policy makers . To highlight how historical records can be used to understand the ecological requirements of threatened species and inform conservation, we investigated sperm whale (Physeter macrocephalus) distribution in the Western Indian Ocean. We assessed differences in information content and habitat suitability predictions based on whale occurrence data from Yankee whaling logs (1792–1912) and from modern cetacean surveys (1995–2020). We built maximum entropy habitat suitability models containing static (bathymetry-derived) variables to compare models comprising historical-only and modern-only data. Using both historical and modern habitat suitability predictions  we assessed marine protected area (MPA) placement by contrasting suitability in- and outside MPAs. The historical model predicted high habitat suitability in shelf and coastal regions near continents and islands, whereas the modern model predicted a less coastal distribution with high habitat suitability more restricted to areas of steep topography. The proportion of high habitat suitability inside versus outside MPAs was higher when applying the historical predictions than the modern predictions, suggesting that different marine spatial planning optimums can be reached from either data sources. Moreover, differences in relative habitat suitability predictions between eras were consistent with the historical depletion of sperm whales from coastal regions, which were easily accessed and targeted by whalers, resulting in a modern distribution limited more to steep continental margins and remote oceanic ridges. The use of historical data can provide important new insights and, through cautious interpretation, inform conservation planning and policy, for example, by identifying refugee species and regions of anticipated population recovery.     

Depth and muscle temperature of Pacific bluefin tuna examined with acoustic and pop-up satellite archival tags

Six Pacific bluefin tuna were tracked with ultrasonic telemetry and two with pop-up satellite archival tags (PSATs) in the eastern Pacific Ocean in 1997, 1998, and 1999. Both pressure and temperature ultrasonic transmitters were used to examine the behavior of the 2- to 4-year-old bluefin tuna. The bluefin spent over 80% of their time in the top 40 m of the water column and made occasional dives into deeper, cooler water. The mean slow-oxidative muscle temperatures of three fish instrumented with pressure and temperature transmitters were 22.0–26.1 °C in water temperatures that averaged 15.7–17.5 °C. The thermal excesses in slow-oxidative muscle averaged 6.2–8.6 °C. Variation in the temperature of the slow-oxidative muscle in the bluefin was not correlated with water temperature or swimming speeds. For comparison with the acoustic tracking data we examined the depth and ambient temperature of two Pacific bluefin tagged with pop-up satellite archival tags for 24 and 52 days. The PSAT data sets show depth and temperature distributions of the bluefin tuna similar to the acoustic data set. Swimming speeds calculated from horizontal distances with the acoustic data indicate the fish mean speeds were 1.1–1.4 fork lengths/s (FL s⁻¹). These Pacific bluefin spent the majority of their time in the top parts of the water column in the eastern Pacific Ocean in a pattern similar to that observed for yellowfin tuna. Received: 4 April 2000 / Accepted: 25 October 2000     

Aggregations and offshore movements as indicators of spawning activity of bonefish (Albula vulpes) in The Bahamas

To identify the timing and location of spawning activity for bonefish (Albula spp.) in the Bahamian archipelago, we used an acoustic telemetry array spanning 44?km² of shallow tidal creeks, flats, and adjacent deeper coastal waters near Cape Eleuthera. In two successive years, we surgically implanted transmitters in male and female bonefish (n?=?60) and examined their movement patterns within the array. Eight bonefish surgically implanted with transmitters as part of an earlier study were also tracked. In 2009, the telemetry information was complemented with snorkeling observations, underwater video, and manual tracking of the same acoustically tagged fish, as well as fish (n?=?3) gastrically implanted with continuous transmitters. During a period of 4?C7?days spanning the full and new moons, primarily between October and May, bonefish moved from their typical shallow flats and aggregated at sites in close proximity to the deep water drop-off of the Exuma Sound. Localized movements of the large schools of bonefish (often?>1,000 fish) at these presumptive pre-spawning aggregation sites included brief trips (<8?h) just after sunset until just prior to sunrise to the abyssal wall at the edge of the Exuma Sound (i.e.,?>1,000?m depth). Tagged bonefish detected at these aggregation sites were subsequently detected back in the tidal creeks and coastal flats shortly after new and full moons and remained at these more typical shallow sites (i.e.,?<2?m depth). Although we did not directly observe spawning events, we did observe ventral nudging and porpoising behaviors, which are potentially associated with courtship. Timing of the observed movements and possible courtship behaviors was coincident with periods when gametes were well developed. Collectively, our study provides the first objective evidence suggesting that the aggregation and seasonal migration of bonefish to deep shelf environments during certain moon phases is for spawning.     

Habitat-induced changes in song consistency affect perception of social status in male chickadees

The ability of male black-capped chickadees to maintain consistent internal structure between successive iterations of their songs is affected by both their social rank and the quality of their habitat. Lab studies reveal that female chickadees discriminate between songs of dominant and subordinate males, which vary in acoustic structure. We investigate whether males also rely on acoustic structure to assess rival quality during agonistic interactions, and whether habitat-induced differences in song consistency affect the perception of male rank. We conducted a playback experiment to simulate territorial intrusions by dominant, stimuli males into the territories of dominant, subject males; stimuli males were recorded either in low-quality (young forest) or high-quality (mature forest) habitats. Stimuli from low-quality habitat had lower song consistency than those from high-quality habitats, despite being recorded from males of equivalent social rank. Subject males for playbacks (also socially dominant males) were chosen from either habitat type. Subject males in mature forest responded less to young-forest stimuli compared to mature-forest stimuli, despite the stimuli in both cases being recorded from dominant males. Conversely, male subjects in young forest did not differentiate between stimuli, but their response to both stimuli was lower than that of mature-forest subject males to mature-forest stimuli. We demonstrate that the ability to maintain internal song structure in the black-capped chickadee constitutes a signal that appears to be used by males to assess the level of threat of intruders, and that this perception is affected by habitat from which the stimulus males were recorded.     

Comparing spatial conservation prioritization methods with site- versus spatial dependency-based connectivity

Larval dispersal is an important component of marine reserve networks. Two conceptually different approaches to incorporate dispersal connectivity into spatial planning of these networks exist, and it is an open question as to when either is most appropriate. Candidate reserve sites can be selected individually based on local properties of connectivity or on a spatial dependency-based approach of selecting clusters of strongly connected habitat patches. The first acts on individual sites, whereas the second acts on linked pairs of sites. We used a combination of larval dispersal simulations representing different seascapes and case studies of biophysical larval dispersal models in the Coral Triangle region and the province of Southeast Sulawesi, Indonesia, to compare the performance of these 2 methods in the spatial planning software Marxan. We explored the reserve design performance implications of different dispersal distances and patterns based on the equilibrium settlement of larvae in protected and unprotected areas. We further assessed different assumptions about metapopulation contributions from unprotected areas, including the case of 100% depletion and more moderate scenarios. The spatial dependency method was suitable when dispersal was limited, a high proportion of the area of interest was substantially degraded, or the target amount of habitat protected was low. Conversely, when subpopulations were well connected, the 100% depletion was relaxed, or more habitat was protected, protecting individual sites with high scores in metrics of connectivity was a better strategy. Spatial dependency methods generally produced more spatially clustered solutions with more benefits inside than outside reserves compared with site-based methods. Therefore, spatial dependency methods potentially provide better results for ecological persistence objectives over enhancing fisheries objectives, and vice versa. Different spatial prioritization methods of using connectivity are appropriate for different contexts, depending on dispersal characteristics, unprotected area contributions, habitat protection targets, and specific management objectives. Comparación entre los métodos de priorización de la conservación espacial con sitio y la conectividad espacial basada en la dependencia     

Performance level and efficiency of two differing predator-avoidance strategies depend on nutritional state of the prey fish

Animal prey has developed a variety of behavioural strategies to avoid predation. Many fish species form shoals in the open water or seek refuge in structurally complex habitats. Since anti-predator strategies bear costs and are energy-demanding, we hypothesised that the nutritional state of prey should modify the performance level and efficiency of such strategies. In aquaria either containing or lacking a structured refuge habitat, well-fed or food-deprived juvenile roach (Rutilus rutilus) were exposed to an open-water predator (pikeperch, Sander lucioperca). Controls were run without predators. In the presence of the predator, roach enhanced the performance of the anti-predator strategy and increased the use of the refuge habitat whereby food-deprived roach were encountered more often in the structure than well-fed roach. Nonetheless more starved than well-fed roach were fed upon by the predator. In the treatments offering only open-water areas, roach always formed dense shoals in the presence of the predator. The shoal density, however, was lower in starved roach. Starving fish in shoals experienced the highest predation mortality across all experimental treatments. The experiment confirmed the plasticity of the anti-predator behaviour in roach and demonstrated that food deprivation diminished the efficiency of shoaling more strongly than the efficiency of hiding. The findings may be relevant to spatial distribution of prey and predator–prey interactions under natural conditions because when prey are confronted with phases of reduced resource availability, flexible anti-predator strategies may lead to dynamic habitat use patterns.