Metabolic Rate and Natural History of Ozark Cavefish, Amblyopsis Rosae, in Logan Cave, Arkansas

We investigated the effects of mass, season, and activity on oxygen consumption of the federally threatened Ozark cavefish, Amblyopsis rosae, at Logan Cave National Wildlife Refuge, Benton County, Arkansas. We used an acclimatization protocol to measure in-situ metabolic rates. There was a significant effect of mass on the metabolic rate of Ozark cavefish and this relationship differed significantly among seasons. We observed a positive relationship between mass and oxygen consumption during summer and autumn but a negative relationship for winter and spring. There was a 1°C water temperature change between summer/autumn sampling and winter/spring sampling, but it is not likely temperature alone accounted for seasonal variation in mass-oxygen consumption relationships. Activity in the respirometer did not vary significantly among seasons and was not correlated with fish mass or time of day. Seasonal relationships between mass and oxygen consumption may therefore reflect alterations in environmental conditions (i.e. food availability, ambient dissolved oxygen), condition, changes in susceptibility to handling stress, or may reflect low numbers of fish tested. Natural history observations were made throughout the study. Four females were seen in late August with ova visible in the body cavity. On 20 June 1996 we first observed five small cavefish (approximately 10 mm TL) in a pool just upstream of the sinkhole entrance that were likely less than a month old. One large adult (55 mm TL) was seen in the same pool with the young fish for six weeks, until two small fish were displaced by a storm event. Although this does not provide a clear sign of parental care, it does suggest that cannibalism is not always the rule for this species as previously suggested.     

Movements and Site Fidelity of two Juvenile Fish Species Using Surf Zone Nursery Habitats Along The Southeastern North Carolina Coast

We examined the extent of movements of juvenile Florida pompano, Trachinotus carolinus, and gulf kingfish, Menticirrhus littoralis, along an open ocean beach. Fishes were collected by seine at three sites along Masonboro Island and Carolina Beach, NC between 7 June and 7 July 1995. All specimens 40 mm standard length (SL) were tagged with coded wire tags and released at the capture sites. Between 7 July and 9 August and on 15–16 September Masonboro Island and northern Carolina Beach were surveyed for tagged fish. A controlled tag mortality/retention study was conducted for both species. Overall, 1569 Florida pompano (40–135 mm SL) were tagged. Sixty-one (3.9%) of these were recaptured, and only eight moved away from the original tagging sites. The largest movements by two Florida pompano were 2.1 and 10.5 km. Many fish remained at their original tagging sites for 21–27 days. Of 488 gulf kingfish (36–158 mm SL) tagged, 16 (3.3%) were recaptured. Gulf kingfish also exhibited little movement away from tagging sites during the study, with individuals remaining at original tagging sites up to 21 days. Stock size estimates for Florida pompano ranged from 3354 to 4670 among the tagging sites, with densities ranging from 1.9 to 2.6 fish m^–2. The remarkable site fidelity exhibited by these two species suggests that resources were not limiting or that predation pressure was not high enough to cause large scale movements during the study. This implies that local disturbances could impact behavior or survival of juvenile fishes in the surf zone.     

The 30-year recovery effort for the Ozark cavefish (<Emphasis Type="Italic">Amblyopsis rosae</Emphasis>): Analysis of current distribution,population trends,and conservation status of this threatened species

Here we review the thirty year recovery effort and conservation status of the Ozark cavefish, Amblyopsis rosae. We summarized the historic and current range of the species, and report county range extensions for both A. rosae and its confamilial Typhlichthys subterraneus. Ozark cavefish survey data spanning almost a century were analyzed for temporal trends using the Mann-Kendall Test/Sen’s Slope Estimator Method. Results were inconclusive because variance was high and the majority of data sets were not sufficiently large to detect a trend. However, the two largest populations (Cave Springs Cave and Logan Cave, Benton Co., Arkansas) have stabilizing or increasing survey counts. While the number of active cavefish sites has decreased over 50% since 1990, the number of surveyed individuals has not. Reasons for endangerment were reanalyzed since federal listing; the primary threat has shifted from overcollection to habitat degradation. We analyzed the progress of recovery task implementation, and we critically evaluated the basis of delisting criteria. Recovery Task 1, the hydrogeologic delineation of subterranean habitats, is almost complete. Recovery Task 2 prescribes protection and management for Recovery Caves, and important progress has been made. Recovery Task 3 involves the development and implementation of monitoring programs in Recovery Caves. Several important studies have been performed, and indicate that many cavefish populations are experiencing chronic, low-level exposure to a suite of anthropogenic contaminants. Delisting conditions are largely unattainable as currently worded. We suggest that recovery criteria be amended such that habitat protection goals are attainable, that the list of Recovery Caves can be periodically updated, and that the recovery population goal is increased and distributed between more sites.     

Habitat and Population Data of Troglobitic Armored Cave Catfish, Ancistrus Cryptophthalmus Reis, 1987, from Central Brazil (Siluriformes: Loricariidae)

Population ecology of the troglobitic armored catfish, A. cryptophthalmus, from caves in São Domingos karst area of central Brazil, was studied in a two-census capture-mark-recapture study carried out during the dry season of 1999. Like many loricariids, including epigean Ancistrus catfishes from that area, A. cryptophthalmus is a typical bottom-dweller with a strong preference for rocky substrates in fast-flowing stream sectors. Relatively high population densities, when compared to other cavefishes, were recorded in the studied cave sections: 0.9 individuals m^–2 in Angélica Cave and 0.5 individuals m^–2 in Passa Três Cave. Passa Três Stream is a small tributary of the São Vicente Cave system, and the estimated population for Passa Três Cave (ca. 2000 m long) is around 1000 individuals. On the other hand, the large Angélica Cave Stream (8 km long) harbors a very large population, conservatively estimated at 20 000 individuals. No fish movements of distances longer than 100 m were recorded in the 40-day period. In Passa Três Cave, a few movements of distances up to 60 m were detected. Proportion of mature females in Angélica Cave was higher than in Passa Três Cave, possibly reflecting a greater food availability in the first cave. Mean individual growth rates in Angélica Cave (1.35 mm month^–1 for size class <41 mm SL, 0.17 mm month^–1 for size class >41 mm SL) point to relatively high longevities, possibly attaining 15 years.     

Behavioral responses of red hake,Urophycis chuss,to decreasing concentrations of dissolved oxygen

Synopsis Laboratory experiments were conducted to examine changes in behavior of red hake,Urophycis chuss, under decreasing concentrations of dissolved oxygen (DO). Since the ecological requirements of this species change with age, responses were measured for three different groups: (1) age 0+, = 89 mm total length (TL); (2) age 1+, = 238 mm TL; and (3) age 2–3+, = 397 mm TL. As DO decreased from 8–10 mg l^-1 to < 0.5 mg l^-1, changes were evident in active time, water column activity, range of horizontal movement, food searching, and agonistic behavior. Age 0+ fish were most sensitive, moving up into the water column and swimming continuously as DO levels fell below 4.2 mg l^-1. Age 2–3+ fish were the least responsive, remaining on the substrate and increasing only their range of movement at concentrations below 3 mg l^-1. Responses of age 1 + fish were variable, possibly reflecting a transition stage between the younger and older fish. Common to all groups was the decrease and eventual cessation of food searching.     

Albinism in phylogenetically and geographically distinct populations of Astyanax cavefish arises through the same loss-of-function Oca2 allele

The Mexican tetra, Astyanax mexicanus, comprises 29 populations of cave-adapted fish distributed across a vast karst region in northeastern Mexico. These populations have a complex evolutionary history, having descended from ‘old'' and ‘young'' ancestral surface-dwelling stocks that invaded the region ∼6.7 and ∼2.8 MYa, respectively. This study investigates a set of captive, pigmented Astyanax cavefish collected from the Micos cave locality in 1970, in which albinism appeared over the past two decades. We combined novel coloration analyses, coding sequence comparisons and mRNA expression level studies to investigate the origin of albinism in captive-bred Micos cavefish. We discovered that albino Micos cavefish harbor two copies of a loss-of-function ocular and cutaneous albinism type II (Oca2) allele previously identified in the geographically distant Pachón cave population. This result suggests that phylogenetically young Micos cavefish and phylogenetically old Pachón cave fish inherited this Oca2 allele from the ancestral surface-dwelling taxon. This likely resulted from the presence of the loss-of-function Oca2 haplotype in the ‘young'' ancestral surface-dwelling stock that colonized the Micos cave and also introgressed into the ancient Pachón cave population. The appearance of albinism in captive Micos cavefish, caused by the same loss-of-function allele present in Pachón cavefish, implies that geographically and phylogenetically distinct cave populations can evolve the same troglomorphic phenotype from standing genetic variation present in the ancestral taxon.     

Nontroglobitic Fishes in Bruffey-Hills Creek Cave, West Virginia, and other Caves Worldwide

Six species of fishes were tagged and released in September and November 1995 and on five dates between November 1998 and October 1999 inside Bruffey-Hills Creek Cave. Most of the tagged fishes were creek chub, Semotilus atromaculatus, and green sunfish, Lepomis cyanellus. The overall recapture rate was 2.6% as only three of 117 fishes were recaptured. Forty-nine days was the longest time of residence by two L. cyanellus and one S. atromaculatus, and movement of 83.4 m was observed only for the creek chub. Tag loss was confirmed as one factor in the low recapture rate. Nine species of fishes were collected in the cave, including Phoxinus oreas and Pimephales promelas, two species never collected in a cave. Most of the fishes were pigmented normally, but many creek chubs were depigmented and appeared white or pigmentless when first observed in the cave stream. Four species, Phoxinus oreas, Pimephales promelas, Ameiurus nebulosus, and Lepomis macrochirus, were collected for the first time in Bruffey-Hills Creek Cave and in the Bruffey and Hills creeks drainage. Although data from this study did not shed light on residence time of fishes in the cave, the consistent occurrence of epigean fishes in this cave was shown. A list of epigean fishes from caves worldwide was included along with a discussion of aspects of the ecology of epigean fishes in caves and of evolution of troglobitic fishes.     

Movements and growth of tagged young-of-the-year Atlantic croaker (Micropogonias undulatus L.) in restored and reference marsh creeks in Delaware Bay, USA

The residence time, movements, and growth of tagged young-of-the-year Atlantic croaker, Micropogonias undulatus L., were studied from July to October 1998 as measures of the success of a marsh restoration project adjacent to Delaware Bay. A total of 8173 croaker (41-121 mm SL) were tagged from each of two creeks in both marshes during July and August with internal sequential coded wire microtags. A prior tag-retention study in the laboratory found a 95% tag retention rate. Of those tagged, 3.6% were recaptured within and nearby the study creeks using seines, otter trawls, and weirs during a 105-day period. Recapture percentages ranged from 1.5% to 6.1% in individual creeks in the restored marsh. There was some movement of tagged fish between creeks in the restored marsh and out into the main creek, but 95% of the recaptures were made in the subtidal and intertidal portions of the same creek in which they were tagged. Fewer fish were recaptured at the reference marsh (1.6% recapture; n=1489 tagged) up to 50 days after tagging, with no evidence of movement between creeks. The average individual growth rates for recaptured croaker was the same in both restored (0.69 mm/day) and reference (0.63 mm/day) marshes before egress from the creeks in September and October. As a result, both created creeks in a restored marsh and natural creeks in a reference marsh appeared to be utilized as young-of-the-year habitat in a similar way during the summer and until egress out of the marshes during the fall, thus this restoration effort has been successful in creating suitable habitat for Atlantic croaker.     

Regional variation in canopy transpiration of Central European beech forests

Forest hydrologists have hypothesised that canopy transpiration (E_c) of European temperate forests occurs at rather similar rates in stands with different tree species and hydrologic regimes. We tested this hypothesis by synchronously measuring xylem sap flow in four mature stands of Fagus sylvatica along a precipitation gradient with the aim (1) of exploring the regional variability of annual canopy transpiration (E_c(t)) in this species, and (2) of analysing the relationship between precipitation (P) and E_c(t). E_c(t) rates of 216, 225, 272 and 303 mm year^–1 corresponded to precipitation averages of 520, 710, 801 and 1,040 mm year^–1 in the four stands. We explored the regional variability of E_c(t) in Central European colline to sub-montane beech stands in two meta-analyses based on (1) existing sap flow data on beech (n=5 observations), or (2) all canopy transpiration data on beech obtained by different techniques (sap flow, micrometeorological or soil water budget approaches, n=25). With a coefficient of variation (CV) of 20%, the regional variability of E_c(t) (213–421 mm year^–1) was smaller than the variation in corresponding precipitation (550–1,480 mm year^–1). The mean E_c(t) for beech was 289 (±58) mm year^–1 (n=25). A humped-shaped relationship between E_c(t) and P, with a broad transpiration maximum in the precipitation range from ca. 700 to 1,000 mm year^–1, was found which may indicate soil moisture limitation of transpiration for P –1, and reduced transpiration by increased cloudiness or leaf wetness for P>1,000 mm year^–1. Thus, the precipitation level significantly influences canopy transpiration of humid temperate forests; however, the size of the P influence on E_c(t) and, in part, the direction of its effect differ from forests in semi-arid or arid climates. European beech has the capacity to maintain high E_c rates in both humid and partly dry summer climates (P<550 mm year^–1).     

Quantifying the activity and movement of perch in a temperate lake by integrating acoustic telemetry and a geographic information system

The horizontal movement patterns of perch (Perca fluviatilis L.) were studied by means of an automatic positioning system in a small Mediterranean temperate lake in northeastern Spain. Seven perch (247–265 mm in fork length, 243–271 g in weight) were implanted surgically with ultrasonic transmitters (38 mm long, 3.5 g in water) and their positions monitored approximately every 180 s using a radio-linked acoustic positioning (VRAP) system. Fish positions were integrated into a geographic information system database with information on date, time, slope and bottom depth. As a measure of the intensity of movement, the swimming speed was calculated. The Minimum Convex Polygon area was obtained as a measure of the area of activity. The data dispersion was calculated as r ² (the mean squared distance from the center of activity). The tagged perch showed individual variations in activity levels, but all had a circadian pattern, being less active at night (average speed 6.0 cm s^–1) than during the day (average speed 10.4 cm s^–1). They exhibited two peaks of activity, at sunrise and sunset. Two patterns of movement emerged, the first characterised by movement between the limnetic and the littoral zones, the second restricted to the shoreline. Fish appeared to follow the same path, reducing the area of activity to a limited part of the lake. Also, fish returned to the same place after movements, showing site fidelity but only for a few days. Overall, although perch could be very abundant in open waters (limnetic zone), they demonstrated a high dependence on the littoral zone.     

Growth and Maximum Size of Tiger Sharks (Galeocerdo cuvier) in Hawaii

Tiger sharks (Galecerdo cuvier) are apex predators characterized by their broad diet, large size and rapid growth. Tiger shark maximum size is typically between 380 & 450 cm Total Length (TL), with a few individuals reaching 550 cm TL, but the maximum size of tiger sharks in Hawaii waters remains uncertain. A previous study suggested tiger sharks grow rather slowly in Hawaii compared to other regions, but this may have been an artifact of the method used to estimate growth (unvalidated vertebral ring counts) compounded by small sample size and narrow size range. Since 1993, the University of Hawaii has conducted a research program aimed at elucidating tiger shark biology, and to date 420 tiger sharks have been tagged and 50 recaptured. All recaptures were from Hawaii except a single shark recaptured off Isla Jacques Cousteau (24°13′17″N 109°52′14″W), in the southern Gulf of California (minimum distance between tag and recapture sites  =  approximately 5,000 km), after 366 days at liberty (DAL). We used these empirical mark-recapture data to estimate growth rates and maximum size for tiger sharks in Hawaii. We found that tiger sharks in Hawaii grow twice as fast as previously thought, on average reaching 340 cm TL by age 5, and attaining a maximum size of 403 cm TL. Our model indicates the fastest growing individuals attain 400 cm TL by age 5, and the largest reach a maximum size of 444 cm TL. The largest shark captured during our study was 464 cm TL but individuals >450 cm TL were extremely rare (0.005% of sharks captured). We conclude that tiger shark growth rates and maximum sizes in Hawaii are generally consistent with those in other regions, and hypothesize that a broad diet may help them to achieve this rapid growth by maximizing prey consumption rates.     

Inter-annual Fidelity to Summer Feeding Sites in Arctic Grayling

Inter-annual fidelity to summer feeding sites was assessed in adult Arctic grayling, Thymallus arcticus, in the Kuparuk River, Alaska using long-term (15 years) records of individually tagged fish. The Kuparuk River has been the site of a long-term fertilization experiment which allowed us to evaluate the effects of habitat quality on site fidelity. Fidelity to the entire 5km experimental reach, the reference or fertilized zone of the river and to specific river locations was examined. On average, 32% of the arctic grayling caught in the experimental reach were recaptured within the reach in subsequent years. Grayling that returned to the reach displayed strong fidelity to river zones as well as to specific sites on the river. More than half of the fish were recaptured within 300meters of the site where they were captured in previous years. There was no significant difference in fidelity to either the reference or the more productive fertilized zone. Unexpectedly, fidelity was unrelated to fish size (29–43cm TL) or previous summers growth. Strong site fidelity appears to be an adaptation to a short summer during which sufficient resources must be acquired to sustain the fish through the long (9 month) Arctic winter leaving little time to explore alternative locations.     

Population size,growth and movements of Anguilla australis in a small lake

To study growth rates, movements and estimate population size of shortfin eels Anguilla australis in a small lake (2·5 ha) near Christchurch, New Zealand, 617 A. australis were tagged with PIT tags. Tag retention was high (95%) and over the seven recapture events spread over 2 years, 55% of tagged A. australis were recaptured. Growth of recaptured A. australis averaged 13·1 mm year^?1 and declined slightly with increasing total length. Distance moved from original capture site increased with increasing time at large. Population estimates of A. australis > 400 mm (susceptible to capture by fyke net) from recaptures of individuals averaged 1451 A. australis, with a biomass of 170 kg ha^?1. An average of 6·6% of the estimated total population matured as male silver A. australis each year. Results from radio‐tracking of four A. australis gave an average nightly foraging area of 2780 m², and there was no apparent preference for inshore movement (within 5–6 m of the shoreline) or offshore movement. Fyke‐net efficiency (total catch relative to the estimated total population available to each net) measured over four consecutive nights fishing was 88%. The lack of precision of the shoreline triangulation system used, ±10 m, meant that the positional data were considered too coarse to be used in a proposed novel population estimation technique based on determining population size within foraging areas.     

Extraordinary growth in tiger sharks Galeocerdo cuvier from the South Atlantic Ocean

Two tagged‐and‐recaptured tiger sharks Galeocerdo cuvier, measuring 172 and 304 cm total length (L_T) and at age 0·75 and 3·50 years, exhibited unmatched growth rates of 118·4 and 55·5 cm year^?1, respectively. The larger fish was nearly mature, indicating that G. cuvier off Brazil could mature considerably earlier than conspecifics from other regions.     

Status of the Federally Endangered Alabama Cavefish, Speoplatyrhinus Poulsoni (Amblyopsidae), in Key Cave and surrounding Caves, Alabama

Speoplatyrhinus poulsoni, the Alabama cavefish, is a federally endangered stygobitic fish that is restricted to Key Cave in northwestern Alabama. Due to the low abundance of this species and the continuous threats to the cave's recharge area, we surveyed Key Cave from 1992 to 1997. Alabama cavefish were present in five different pools and had numbers comparable to previous surveys performed in the 1970's and 1980's. Three different size classes were observed, indicating recruitment is occurring. These data suggest that the population is relatively stable, but future monitoring is recommended. The Alabama cavefish is an endangered species and is extremely difficult to capture, therefore any marking program to accurately estimate the population size is unlikely. A single specimen of Typhlichthys subterraneus was captured in Key Cave. This falsifies the previous assumption that these two species are allopatric. Because of this discovery, we resurveyed seven caves in the area around Key Cave for additional populations of S. poulsoni. These caves had either known populations of T. subterraneus or unidentified cavefish. No additional populations of S. poulsoni were discovered, but further investigation is warranted. The Key Cave National Wildlife Refuge was established in the high recharge area of Key Cave to protect this habitat, yet threats to the groundwater continue from encroaching urbanization.     

Water chemistry and nutrient budgets in an undisturbed evergreen rainforest of southern Chile

In a pristine evergreen rainforest of Nothofagus betuloides, located at the Cordillera de los Andes in southern Chile (41 °S), concentrations and fluxes of nutrients in bulk precipitation, cloud water, throughfall water, stemflow water, soil infiltration and percolation water and runoff water were measured. The main objectives of this study were to investigate canopy-soil-atmosphere interactions and to calculate input-output budgets. From May 1999 till April 2000, the experimental watershed received 8121 mm water (86% incident precipitation, 14% cloud water), of which the canopy intercepted 16%. Runoff water volume amounted 9527 mm. Bulk deposition of inorganic (DIN) and organic (DON) nitrogen amounted 3.6 kg ha^–1 year^–1 and 8.2 kg ha^–1 year^–1 respectively. Occult deposition (clouds + fog) contributes for 40% to the atmospheric nitrogen input (bulk + occult deposition) of the forest. An important part of the atmospheric ammonium deposition is retained within the canopy or converted to nitrate or organic nitrogen by epiphytic bacteria or lichens. Also the export of inorganic (0.9 kg ha^–1 year^–1) and organic (5.2 kg ha^–1 year^–1) nitrogen via runoff is lower than the input to the forest floor via throughfall and stemflow water (3.2 kg DIN ha–1 year^–1 and 5.6 kg DON ha^–1 year^–1). The low concentrations of NO ₃ ^– and NH ₄ ⁺ under the rooting depth suggest an effective biological immobilization by vegetation and soil microflora. Dry deposition and foliar leaching of base cations (K⁺, Ca²⁺, Mg²⁺) was estimated using a canopy budget model. Bulk deposition accounted for about 50% of the total atmospheric input. Calculated dry and occult deposition are both of equal value (about 25%). Foliar leaching of K⁺, Ca²⁺, and Mg²⁺ accounted for 45%, 38% and 6% of throughfall deposition respectively. On an annual basis, the experimental watershed was a net source for Na⁺, Ca²⁺ and Mg²⁺.     

Movement and growth of juvenile (age 0 and 1+) tautog (Tautoga onitis [L.]) and cunner (Tautogolabrus adspersus [Walbaum]) in a southern New Jersey estuary

The extent to which individual juvenile fish occupy specific sites is largely unknown. This complicates efforts to identify optimum habitats and habitat-specific information such as growth and mortality rates which, in turn, can influence recruitment success. Using tag-recapture information, we examined movements and growth of juvenile tautog (Tautoga onitis [L.]) and cunner (Tautogolabrus adspersus [Walbaum]) in Great Bay-Little Egg Harbor estuaries in southern New Jersey. Fishes were trapped, tagged with small disks (bee tags), released in an embayment (mean depth = 2.5 m, mean salinity = 28‰) adjoining a tidal creek and recaptured from April through November 1992. Of 729 tautog (25-187 mm TL) released, there were 228 recaptures (31%) of 114 individuals, with a high percentage of recaptured individuals (37%) caught more than once (up to 13 times) during nearly 3 months at liberty. Of 410 cunner (24-99 mm TL) released, there were 95 recaptures (23%) of 66 individuals of which 30% were recaptured repeatedly (up to 6 times) over a 2-month period in summer and fall. Recaptured individuals of both species generally moved relatively little (< 22 m) from the common release site even though recapture efforts occurred over the scale of meters to kilometers. Age 1+ individuals tended to travel shorter distance than age 0 individuals for both species. The short distance traveled and high recapture rates indicate that these species exhibited strong site fidelity. The mean growth of both species was 0.25 mm day^− 1 from spring through fall although growth varied between species, age class and season. These movement and growth characteristics indicate that at least some of the 0+ individuals “settle and stay” and 1+ individuals “return and stay” in estuarine habitats. The high site fidelity, in this and other studies, implies that growth rates may be good measures of habitat quality for tautog and cunner at least from spring through fall.     

Patterns of nocturnal movement of the long-spined sea urchin<Emphasis Type="Italic"> Diadema antillarum</Emphasis> (Philippi) in Gran Canaria (the Canary Islands,central East Atlantic Ocean)

We tagged individuals of the sea urchin Diadema antillarum (Philippi) around the island of Gran Canaria (The Canary Islands) during winter 2001–2002 using a new technique, consisting of the insertion of a hook fastened to a fishing line into the aboral pole (periproctal membrane). This allowed individual identification of tagged sea urchins. The goals were: (1) to quantify nocturnal movements and the homing behaviour of this echinoid on shallow rocky bottoms, and (2) to assess short term spatial and temporal variability of these movements. Tagged sea urchins displayed clear homing behaviour. The mean distance travelled at night was 3.7±1.2 m (range 1.0–5.1 m). Mean speed of nocturnal movement was 33±26 cm h^–1 (range 5–110 cm h^–1). We observed greater movement at midnight than at the beginning and the end of the night.Communicated by H.-D. Franke     

A Potential Benefit of Albinism in Astyanax Cavefish: Downregulation of the oca2 Gene Increases Tyrosine and Catecholamine Levels as an Alternative to Melanin Synthesis

Albinism, the loss of melanin pigmentation, has evolved in a diverse variety of cave animals but the responsible evolutionary mechanisms are unknown. In Astyanax mexicanus, which has a pigmented surface dwelling form (surface fish) and several albino cave-dwelling forms (cavefish), albinism is caused by loss of function mutations in the oca2 gene, which operates during the first step of the melanin synthesis pathway. In addition to albinism, cavefish have evolved differences in behavior, including feeding and sleep, which are under the control of the catecholamine system. The catecholamine and melanin synthesis pathways diverge after beginning with the same substrate, L-tyrosine. Here we describe a novel relationship between the catecholamine and melanin synthesis pathways in Astyanax. Our results show significant increases in L-tyrosine, dopamine, and norepinephrine in pre-feeding larvae and adult brains of Pachón cavefish relative to surface fish. In addition, norepinephrine is elevated in cavefish adult kidneys, which contain the teleost homologs of catecholamine synthesizing adrenal cells. We further show that the oca2 gene is expressed during surface fish development but is downregulated in cavefish embryos. A key finding is that knockdown of oca2 expression in surface fish embryos delays the development of pigmented melanophores and simultaneously increases L-tyrosine and dopamine. We conclude that a potential evolutionary benefit of albinism in Astyanax cavefish may be to provide surplus L-tyrosine as a precursor for the elevated catecholamine synthesis pathway, which could be important for adaptation to the challenging cave environment.     

Ecology of Allis Shad Alosa alosa and Twaite Shad Alosa fallax in the Solway Firth, Scotland

The basis of this study were 132 adult Allis Shad and 150 Twaite Shad collected as bycatches from salmon stake nets in Scotland on the north side of the Solway Firth. Most (60%) of the Allis Shad were immature fish 2–3 years of age (mean length 305 mm). Mature males were younger (3–5 years) and smaller (mean length 421 mm) than females (4–6 years and 481 mm mean length). The largest Allis Shad was a female of 515 mm and 2183 g. In contrast, almost all the Twaite Shad were mature, the males younger (3–5 years) and smaller (mean length 341 mm) than the females (4–6 years and 364 mm mean length). The largest Twaite Shad was a female of 400 mm and 1213 g. The food of Allis Shad consisted mainly of small zooplankton with some fish and larger Crustacea. Fine vegetable fragments were common in the stomachs and attributed to filter feeding. The food of Twaite Shad was mainly small fish with some Crustacea. Mature Allis Shad of both sexes with large gonads (maximum female GSI: 20.63) were found throughout the spring and summer but no definite evidence of local spawning was obtained. Mature Twaite Shad of both sexes with large gonads (maximum female GSI: 23.32) were found until early July, thereafter most of the fish were spent. It appears that Twaite Shad spawn locally in June. Some hybrids between the two species were found.