Expulsion of miniature radio transmitters along with eggs of muskellunge and northern pike––a new method for locating critical spawning habitat

Identification and protection of critical spawning habitat for muskellunge Esox masquinongy and northern pike Esox lucius is important for preserving the reproductive potential of both species. In this study, we implanted miniature radio transmitters through the oviduct into the egg masses of female muskellunge and northern pike just prior to spawning. This non-surgical procedure was a novel approach for identifying spawning sites when transmitters were expelled with the eggs during egg deposition. Preliminary studies in three lakes showed that muskellunge and northern pike deposited many of the transmitters in likely spawning habitat. An inability to find eggs limited our validation of this method, but nevertheless, a relatively high proportion (70%) of northern pike larger than 690 mm (27.2 inches) expelled transmitters in a previously known spawning area in Willow Lake, Minnesota. Shoreline vegetation in that area consisted primarily of sedges Carex spp., and the adjacent water was shallow with substrate consisting of large mats of water bulrush Scirpus subterminalis. A lower proportion (50%) of muskellunge expelled transmitters in Elk Lake, Minnesota. Water depth at likely spawning sites averaged 1.1 m (3.6 feet) and vegetative cover was variable, but Chara spp. was common to most sites. In Moose Lake, Minnesota, containing sympatric populations of muskellunge and northern pike, 60% of muskellunge and 90% of pike expelled transmitters. Chara spp. beds were the predominant substrate where transmitters were expelled in Moose Lake, but the two species deposited transmitters on deepwater bars (3.7–5.2 m) in addition to shallow near-shore habitat. These results suggest more flexibility in depths used for spawning than typically reported for muskellunge and northern pike.     

Habitat selection and segregation by two sympatric lagomorphs: the case of European hares (<Emphasis Type="Italic">Lepus europaeus</Emphasis>) and Eastern cottontails (<Emphasis Type="Italic">Sylvilagus floridanus</Emphasis>) in northern Italy

In northern Italy, the native European hare (Lepus europaeus) and the introduced Eastern cottontail (Sylvilagus floridanus) can occur together at a local scale, as a result of cottontail introduction and expansion into the European hare range. Hare populations are limited in Italy by habitat loss, diseases, and most important by overhunting, and many areas within hare range in northern Italy are undergoing increasing anthropogenic impact. Therefore, quantitative studies on resource selection and exploitation by both species will be of great interest to evaluate the degree of habitat overlap and to search for exploitation competition evidences. We studied habitat selection during resting time by both species in two areas where they occur alone and in one area where they occur together. Habitat selection by the two species was examined at micro- and macro-habitat scales during autumn–winter and spring–summer. Both species selected ecotonal zones between arboriculture stands and crops and between arboriculture stands and spontaneous vegetation (i.e., herbaceous, bush, and woody permanent species), which were the less available in the area of sympatry. No habitat shifts were evident at macro-habitat level because the two species showed a differential micro-habitat use within patches. On the whole, it seems that habitat heterogeneity promoted daytime segregation between the two species. In particular, edges between crops and canopy habitats should be improved, thus reducing chance of intra- and inter-specific encounters.     

The impact of catch-and-release angling on short-term behaviour and habitat choice of northern pike (<Emphasis Type="Italic">Esox lucius</Emphasis> L<Emphasis Type="Italic">.</Emphasis>)

In the northern hemisphere, pike (Esox lucius Linnaeus) is one of the most important recreational fisheries resources, and regulatory or voluntary catch-and-release angling is common. No information is available about the potential sublethal impacts on pike that catch-and-release fishing may cause, such as behavioural alterations and changes in habitat choice after release. Radio telemetry with N = 20 pike was used to test the hypothesis that fish modify behaviour by reducing movement as a reaction to a catch-and-release event in a previously unfished, slightly eutrophic lake, having an area of 25 ha and located in northeastern Germany. During a 7-month tracking period, activity of pike was monitored for consecutive 24 h every week. Minimum displacement per hour (m) and distance to shore (m) were significantly lower upon the first post release tracking compared to tracking before the capture. Two tracking events after capture, both movement and distance to shore were similar to those measured during pre-angling. There were no significant relations between the change in movement and distance to shore and size of pike. In terms of habitat choice, pike significantly selected for reed and avoided the pelagic area over the whole study period that was not influenced by catch-and-release angling. The results indicated that catch-and-release induces short-term behavioural alterations in pike, probably explained by physiological disturbances and facilitated by evolved anti-predation behaviours. Such alterations, however, seem to be of short duration and reversible suggesting sublethal catch-and-release impacts on pike behaviour are limited. Guest editors: J. M. Farrell, C. Skov, M. Mingelbier, T. Margenau & J. E. Cooper International Pike Symposium: Merging Knowledge of Ecology, Biology, and Management for a Circumpolar Species     

Effects of <Emphasis Type="Italic">Caulerpa racemosa</Emphasis> var. <Emphasis Type="Italic">cylindracea</Emphasis> on prey availability: an experimental approach to predation of amphipods by <Emphasis Type="Italic">Thalassoma pavo</Emphasis> (Labridae)

Alien plant species, such as Caulerpa racemosa var. cylindracea, that invade Mediterranean marine vegetated habitats can affect habitat structure. In turn, changes in habitat structure may affect the associated invertebrate assemblages, either through changes in habitat selection or as a result of altered predation efficiency. In order to test for effects of changes in habitat structure resulting from colonization by C. racemosa on prey availability for predators, the importance of amphipods as a trophic resource in natural vegetated habitat was first assessed, and later experiments were undertaken to assess the effects of the alien alga on predation by Thalassoma pavo of two dominant amphipods: Elasmopus brasiliensis (Gammaridea) and Caprella dilatata (Caprellidea). Laboratory experiments were conducted in separate aquaria with five vegetation habitat types: Halopteris scoparia, Jania rubens, C. racemosa without detritus, C. racemosa with detritus, Cymodocea nodosa, together with controls. The vegetation was first defaunated, and then 30 amphipods were introduced to each aquarium and exposed to a single Thalassoma pavo individual for 1 h, after which the fish’s gut contents were examined. Consumption (per fish per hour) of caprellids (11.7 ± 1.4) was higher overall than that of gammarids (8.7 ± 1.5) and likely reflects different microhabitat use by amphipods, which affects susceptibility to predators. Consumption of amphipods also varied by habitat type. The highest predation rate was found in the C. nodosa habitat (12.7 ± 2.19) and the lowest in the C. racemosa habitats with detritus (4.1 ± 1.78) and without detritus (5.2 ± 0.55), which did not differ. The pattern of predation across habitats, however, was similar for both caprellid and gammarid amphipods, indicating a more general effect of habitat on amphipod predation. Our findings showed that invasive species such as C. racemosa can decrease feeding by predators such as T. pavo. Changes in predator–prey interactions could have consequences for food web support in the Mediterranean.     

Spawning habitat in the spined loach, <Emphasis Type="Italic">Cobitis taenia</Emphasis> (Cypriniformes: Cobitidae)

Spawning habitat of the endangered spined loach Cobitis taenia was studied in northwestern Germany. The distribution of eggs of the loach in the field was best correlated with the density of vegetation but had little correlation with current velocity, water depth, or bottom substrate. In the aquarium, the loach chose dense vegetation for an oviposition site, as inferred by the direct observations of spawning and the location of spawned eggs. It is concluded that such habitat specialization is an important element in the autecology of the endangered fish and a critical stage in the habitat requirements of its populations.     

The biology of the spiny icefish <Emphasis Type="Italic">Chaenodraco wilsoni</Emphasis> Regan, 1914

The most abundant ice fish species observed in catches off the northern tip of the Antarctic Peninsula in the last 25–30 years has been the spiny ice fish Chaenodraco wilsoni Regan 1914. C. wilsoni has been exploited on a commercial scale from the late 1970s to the end of the 1980s off Joinville–D’Urville Islands (CCAMLR Statistical Subarea 48.1) and in the Cosmonauts and Cooperation Seas and Prydz Bay in the Indian Ocean sector (CCAMLR Statistical Division 58.4.2). This paper presents new information on biological features and life history characteristics of C. wilsoni, based on research survey collections along the northern Antarctic Peninsula in 2006 and 2007 and samples taken in the commercial fishery in 1987. Length frequency compositions from the research surveys demonstrated that fish 21–34 cm long predominated in the catches. Sexual maturity is attained at 24–25 cm. Absolute fecundity and relative fecundity is low (1,000–2,500 eggs; 6–12 eggs). Oocyte diameter varied from 4.0 to 4.9 mm very close to spawning. Spawning at the tip of the Antarctic Peninsula is likely to occur in October–November. Remotely operated vehicle deployments in the northern Weddell Sea demonstrated that C. wilsoni exhibit parental nest guarding where males protect the eggs. The incubation period is likely to be 8 months long. Fish feed primarily on Antarctic krill (Euphausia superba) in the Antarctic Peninsula region and in the Cosmonauts and Cooperation Seas while fish take ice krill (Euphausia crystallorophias), Pleuragramma antarcticum and myctophids to some extent in other areas. Age determination still awaits validation. Preliminary ageing attempts suggested a maximum age of about 8–10 years.     

Spawning population characteristics of pike <Emphasis Type="Italic">Esox lucius</Emphasis> L. in Lake Rubikiai (Lithuania)

The aim of the study was to describe the peculiarities of pike spawning in mesotrophic Lake Rubikiai, to determine the spawning population structure and evaluate the influence of some environmental factors on year-class strength formation. The data were collected in April and May (1994–2011). A total of 1586 individuals were caught. The age of pike ranged from 1 to 12 years; 2–5-yearold males (96.0%) and 3–8-year-old females (89.1%) prevailed. The overall sex ratio of females to males was 1:4.1. One-year-old spawning males (26.5–28.5 cm) and two-year-old spawning females (31.5–35.5 cm) constituted 2.1% and 2.6%, respectively. Water temperature during the spawning period was relatively stable, between 4 and 6°C, during March and increased slightly towards 10°C in the middle of April. No correlation was observed between female length and spawning date. Year-class strength did not correlate with the last day of ice presence and the minimal water level at the end of spawning (WL_min), but statistically significantly negatively correlated with the maximum water level at the beginning of spawning (WL_max) and the difference between WL_max and WL_min. The mean annual survival rate for pike (aged ≥2) was 0.74 and the mean annual instantaneous mortality rate was 0.45.     

Space use patterns of mountain hare (<Emphasis Type="Italic">Lepus timidus</Emphasis>) on the Alps

Populations on the limits of species’ distribution can show different behavioral adaptations to strong ecological pressure than in the central part of the range. We investigated space use patterns of alpine mountain hare (Lepus timidus) at two areas on the southern edge of the species’ range. We monitored 34 hares between 2005 and 2008, estimating home range size, overlap, and site fidelity, and compared our results with space use in Scottish and North-European populations. Home ranges of mountain hares did not differ between two study areas with different habitat types. Subadult animals used larger ranges than adults and both age groups reduced home range size in autumn, a period that might be critical for hares due to changes in diet and/or high energy expenditure during the previous breeding season. Home ranges in these alpine populations were smaller than in Scandinavian populations but within the range of populations in different habitat types in Scotland. Seasonal home ranges overlapped considerably, but differed among the sexes: male–female overlap was higher than same sex (male–male and female–female) spatial overlap. Seasonal shifts of home ranges were small, and site fidelity remained high over the seasons, suggesting that resource distribution remained constant throughout the year and that the knowledge of an intensively frequented area is an important element of habitat quality. We concluded that habitat structure and availability of mates interact in affecting mountain hare space use in alpine habitats.     

Identifying conservation priority ponds of an endangered minnow, <Emphasis Type="Italic">Pseudorasbora pumila</Emphasis>, in the area invaded by <Emphasis Type="Italic">Pseudorasbora parva</Emphasis>

We investigated the occurrence pattern of the pond-living endangered cyprinid, Pseudorasbora pumila, and also compared its habitat characteristics with those of the congeneric invasive species, Pseudorasbora parva, in the contact zone. Comparison of 16 environmental variables among the P. pumila habitats, P. parva habitats, and unoccupied ponds revealed that conductivity was a common limitation factor of distribution of both species. We found that emergent vegetation occupancy along the pond bank was the most important factor determining P. pumila occurrence and that ponds with steep banks may have a low probability of containing P. parva. We constructed a logistic regression model to predict the establishment risk of P. parva in ponds occupied by P. pumila. The model demonstrated that more than half of the ponds exhibited a high establishment risk of P. parva. Principal component analysis using six parameters selected from stepwise logistic regression analysis revealed that seven unoccupied ponds had the potential to sustain P. pumila, suggesting that our study site is capable of supporting more P. pumila populations and expanding the current range.     

Reproductive strategies in female polar and deep-sea bobtail squid genera <Emphasis Type="Italic">Rossia</Emphasis> and <Emphasis Type="Italic">Neorossia</Emphasis> (Cephalopoda: Sepiolidae)

Female reproductive features have been investigated in five polar and deep-sea bobtail squid genera Rossia and Neorossia (R. macrosoma, R. moelleri, R. pacifica, N.c. caroli and N.c. jeannae). These species are characterized by asynchronous ovary maturation, very large eggs (>10% ML), fecundity of several hundred oocytes, very high reproductive output, and continuous spawning with low batch fecundity. This adaptive complex of reproductive traits evolved in these small animals as an optimum strategy for polar and deep-water habitats.     

Eggs and larvae of <Emphasis Type="Italic">Awaous melanocephalus</Emphasis> (Teleostei: Gobiidae)

The morphology of eggs and larvae of Awaous melanocephalus is described. The eggs measured 0.33–0.35 mm in long-axis diameter and 0.32–0.34 mm in short-axis diameter. Newly hatched larvae (0.90–0.99 mm in notochord length, NL; 0.93–1.04 mm in total length, TL) were poorly developed, lacking a mouth and having a large yolk sac and unpigmented eyes. The mouth opened and the eyes became fully pigmented 3 days after hatching (1.78–2.00 mm NL, 1.88–2.10 mm TL). The yolk sac was completely absorbed 5 days after hatching at a water temperature of 27°–28°C.     

Tolerance of nonindigenous cichlid fishes (<Emphasis Type="Italic">Cichlasoma urophthalmus</Emphasis>, <Emphasis Type="Italic">Hemichromis letourneuxi</Emphasis>) to low temperature: laboratory and field experiments in south Florida

The cold tolerance of two non-native cichlids (Hemichromis letourneuxi and Cichlasoma urophthalmus) that are established in south Florida was tested in the field and laboratory. In the laboratory, fishes were acclimated to two temperatures (24 and 28°C), and three salinities (0, 10, and 35 ppt). Two endpoints were identified: loss of equilibrium (11.5–13.7°C for C. urophthalmus; 10.8–12.5°C for H. letourneuxi), and death (9.5–11.1°C for C. urophthalmus; 9.1–13.3°C for H. letourneuxi). In the field, fishes were caged in several aquatic habitats during two winter cold snaps. Temperatures were lowest (4.0°C) in the shallow marsh, where no fish survived, and warmest in canals and solution-holes. Canals and ditches as shallow as 50 cm provided thermal refuges for these tropical fishes. Because of the effect on survival of different habitat types, simple predictions of ultimate geographic expansion by non-native fishes using latitude and thermal isoclines are insufficient for freshwater fishes.     

<Emphasis Type="Italic">Catenaria anguillulae</Emphasis> Sorokin: a Natural Biocontrol Agent of <Emphasis Type="Italic">Meloidogyne graminicola</Emphasis> Causing Root Knot Disease of Rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Summary Catenaria anguillulae parasitized and killed the eggs and second stage juveniles (J₂) of Meloidogyne graminicola under natural conditions. The percentage of infection in eggs was higher than J₂ of M.␣graminicola, which ranged between 0–50.3% and 0–18.9% in 2004 and 0–46.6% and 0–21.7% in 2005, respectively. The higher parasitism of eggs and J₂ was recorded from those fields in which plants were severely infected with M. graminicola. The degree of parasitism of eggs and J₂ by C. anguillulae varied with severity of root knot disease. The fields with a higher root gall index recorded a higher percentage of infection in eggs and J₂ of M. graminicola. In general, old galls when teased and incubated, recorded higher parasitism of eggs and juveniles than young galls.     

Lifestyle of Korean mudskipper <Emphasis Type="Italic">Periophthalmus magnuspinnatus</Emphasis> with reference to a congeneric species <Emphasis Type="Italic">Periophthalmus modestus</Emphasis>

To investigate the life history and ecology of the mudskipper Periophthalmus magnuspinnatus, observations and collection were made on coastal mudflats in southern Korea. Periophthalmus magnuspinnatus was active from May to September on the mudflats, exclusively occupying rough and elevated or sloped mudflats of the seashore or the stream mouth, usually vegetated with halophilous grasses. The congeneric species, P. modestus, mainly occurred on extensive low-elevation and level mudflats with no visible vegetation. An apparent alternation of habitat use by P. modestus took place on mudflats at the stream mouth in mid-October, when P. magnuspinnatus began wintering in its burrow and P. modestus came onto the vacated mudflats to construct burrows for wintering. The active season for P. magnuspinnatus at 17°C or higher air temperature was a little shorter than that of P. modestus. Periophthalmus magnuspinnatus constructed a burrow for the entire season in the highest area of the intertidal mudflat, where they hid themselves during high tide or when frightened, whereas P. modestus were likely to use any burrow constructed by other animals or sunken places to hide. The main stomach contents of P. magnuspinnatus were crabs and gammarids. During the reproductive season from May to July, P. magnuspinnatus performed mating behaviors and constructed a spawning burrow similar to the ones known for P. modestus, except their body color turned dark and quivering body movements were observed in the mature male instead of a pink or orange body color and wiggling body movements as in P. modestus. Eggs, measuring 1.56–1.69 mm in major axis and 0.94–1.0 mm in minor axis, were laid on the ceiling and the side wall of the “J”-shaped spawning room generally known for Periophthalmus species. Young of both species started to occur on the mudflat in June.     

Different thermal stimuli initiate hatching of <Emphasis Type="Italic">Daphnia</Emphasis> diapausing eggs originating from lakes and temporary waters

The simultaneous hatching of Daphnia resting eggs from a number of different lakes and ponds using one set of hatching cues can be difficult to achieve as environmental conditions differ considerably between water bodies. Therefore, optimal hatching conditions for ephippial eggs originating from shallow temporary waters may differ from those found in large lakes. The aim of our study was to compare the optimal thermal conditions for hatching ephippial eggs of Daphnia found in permanent lakes and those from shallow temporary ponds. We used ephippial eggs of Daphnia from the longispina species complex originating from two temporary city ponds and two deep lakes in Poland. The ephippia were protected against overheating at all stages of the field and laboratory work to prevent activation or killing of the eggs. After a refractory period (imposed storage in cool and dark conditions), ephippia were incubated at six different temperatures (6, 9, 12, 15, 18 and 21 °C) under a 16:8 L:D light regime. Our results indicate that hatching of resting eggs of Daphnia that inhabit lakes or ponds may require different thermal conditions. The hatching success of ephippial eggs originating from temporary waters was relatively high (30–56%) at all tested incubation temperatures, while for the ephippial eggs from the deep lakes it was lower (7–37%) and inversely related to water temperature. The divergent hatching responses of the ephippial eggs originating from temporary pools and lakes may reflect the typical thermal conditions during hatching in their native habitats. While in the deep lakes of the temperate zone Daphnia hatching typically occurs during the low water temperatures of early spring, in shallow ponds Daphnia hatching may occur throughout the year at varying water temperatures, from a few to over a dozen degrees Celsius.     

Habitat overlap between sympatric European hares (<Emphasis Type="Italic">Lepus europaeus</Emphasis>) and Eastern cottontails (<Emphasis Type="Italic">Sylvilagus floridanus</Emphasis>) in northern Italy

In northern Italy, the range of the Eastern cottontail (Sylvilagus floridanus) largely overlaps with that of the native European hare (Lepus europaeus) on the Po Plain. Both species appear to have similar habitat requirements. We studied habitat selection by hares and cottontails during feeding activity from September 2006 to August 2007 in two areas where they occur alone (allopatry) and in one area where they occur together (sympatry). The three areas were basically similar, so that shifts in habitat use observed in sympatry should reflect the response to interspecific competition. Habitat selection was examined at micro- and macro-habitat levels throughout seasons. Habitat breadth of both species followed the change of resource availability through seasons in allopatry as well as in sympatry. No shifts in habitat use were evident at macro-habitat level, even during autumn which was the limiting season. Exploitation of shared habitats by the two species seems to be promoted by differential micro-habitat use within macro-habitat types. Cottontails used woods with dense understory in greater proportion than hares, and their present sites were concentrated within the maximum distance of 20 m of the nearest shelter site. Hares were more likely than cottontails to exploit crops, and their sites were distributed even greater than 80 m away from permanent cover patches. The habitat heterogeneity of agricultural ecosystems within the sympatry range could buffer the negative effects of external factors (climate, human disturbance and predation) on hares, and enhance the chances of exploitation of shared habitats by both species.     

Accompanying vegetation in young <Emphasis Type="Italic">Pinus radiata</Emphasis> plantations enhances recolonization by <Emphasis Type="Italic">Ceroglossus chilensis</Emphasis> (Coleoptera: Carabidae) after clearcutting

The replacement of native forests by Pinus radiata plantations modifies habitat availability and quality for wildlife, constituting a threat to species survival. However, the presence of understory in mature pine plantations minimizes the negative impacts of native forest replacement, rendering a secondary habitat for wildlife. Whether forest-dwelling species recolonize clear-felled areas pending on the spontaneous development of accompanying vegetation growing after harvesting is yet to be assessed. In this context, we analyze the abundance, movement and habitat selection of the endemic ground beetle Ceroglossus chilensis (Coleoptera: Carabidae) in an anthropic forest landscape consisting of native forest remnants, adult pine plantations (>?20 years) with a well-developed understory, and young (1–2 years) pine plantations with varying degrees of accompanying vegetation development. Particularly, we analyze the likelihood that C. chilensis would recolonize young pine plantations depending on the presence (>?70% cover) or the absence (<?20% cover) of this accompanying vegetation. C. chilensis shows a greater probability of selecting habitats with understory (pine plantations and native forest) and young plantations with accompanying vegetation (future understory) than habitats without such vegetation. Movement of C. chilensis also favors their permanence in habitats with understory vegetation, coinciding with higher abundances than in young pine plantations devoid of accompanying vegetation. Hence, the effect of clearcutting could be mitigated by allowing the development of accompanying vegetation into a future understory, which facilitates the recolonization of pine plantations and its use as secondary habitat for wildlife.     

Variation of acharan sulfate and monosaccharide composition and analysis of neutral <Emphasis Type="Italic">N</Emphasis>-glycans in African giant snail (<Emphasis Type="Italic">Achatina fulica</Emphasis>)

Acharan sulfate content from African giant snail (Achatina fulica) was compared in eggs and snails of different ages. Acharan sulfate was not found in egg. Acharan sulfate disaccharide →4)-α-d-GlcNpAc (1→4)-α-l-IdoAp2S(1→, analyzed by SAX (strong-anion exchange)–HPLC was observed soon after hatching and increases as the snails grow. Monosaccharide compositional analysis showed that mole % of glucosamine, a major monosaccharide of acharan sulfate, increased with age while mole % of galactose decreased with age. These results suggest that galactans represent a major energy source during development, while acharan sulfate appearing immediately after hatching, is essential for the snail growth. The structures of neutral N-glycans released from eggs by peptide N-glycosidase F (PNGase F), were next elucidated using ESI-MS/MS, MALDI-MS/MS, enzyme digestion, and monosaccharide composition analysis. Three types of neutral N-glycan structures were observed, truncated (Hex_2–4-HexNAc₂), high mannose (Hex_5–9-HexNAc₂), and complex (Hex₃-HexNAc_2–10) types. None showed core fucosylation.     

Nematicidal activity of culture filtrate of <Emphasis Type="Italic">Beauveria bassiana</Emphasis> against <Emphasis Type="Italic">Meloidogyne hapla</Emphasis>

Culture filtrates of Beauveria bassiana at different concentrations were evaluated for nematicidal activity against the northern root knot nematode (Meloidogyne hapla); bioassays included egg hatching, mortality and infectivity on tomato plants in pots under glasshouse conditions. The percentage mortality and inhibition of hatching of root-knot nematode were directly proportional to the concentration of culture filtrates of B. bassiana. Soil drenching with culture filtrate of B. bassiana significantly reduced nematode population densities in soil and in the roots and subsequent gall formation and egg-mass production by M. hapla under glasshouse conditions.     

Temporal and spatial patterns of organic carbon are linked to egg deposition by beach spawning horseshoe crabs (<Emphasis Type="Italic">Limulus polyphemus</Emphasis>)

The spring spawning by the American horseshoe crab (Limulus polyphemus L.) results in temporally and spatially discrete inputs of eggs onto sandy beaches in Delaware Bay, USA. We tested the hypothesis that seasonal patterns of sediment organic carbon on Delaware Bay beaches is linked to this pulsed input of horseshoe crab eggs. At a location with minimal horseshoe crab spawning activity (Higbee Beach), there was little seasonal variation in sediment organic carbon, no distinction between organic carbon levels as a function of shoreline position or sediment depth, and no significant correlation between the abundance of crab eggs and percent organic carbon. Conversely, at a prime horseshoe crab spawning habitat (North Beach), organic carbon levels were seasonally pulsed and were correlated with egg abundance. Moreover, the strongest evidence of seasonality was seen at the middle foreshore location at the 15–20 cm depth, consistent with the highest input of horseshoe crab eggs. Although some of the organic carbon contributed by horseshoe crab eggs in May–June leaves the beach in the form of hatched larvae later in the year, there is a net input of organic carbon to the system in the form of unfertilized and/or dead eggs, egg membranes, and embryonic molts. We suggest that the inputs of eggs from horseshoe crabs and other beach spawning animals, such as grunion and capelin, make significant contributions to the energy budget of sandy beaches.