Female Round Gobies Research Articles

Consistent life history shifts along invasion routes? An examination of round goby populations invading on two continents

AbstractAimMany invasive populations exhibit dynamic life history shifts along their invasion route. We investigated whether these shifts represent consistent biological responses of a given species to range expansion, even in systems located in different geographic regions.LocationNorth‐eastern France, Central Ontario (Canada).MethodWe investigated population density, life history traits and age‐specific reproductive investment in expanding populations of round goby at three invasion stages (expansion front, area colonized one year earlier and area colonized for ~five years) along the invasive routes in two river systems differing in climate and system productivity. Interindividual variability, shown to affect range expansion rates, was also investigated along the invasion routes. The study was based on female round gobies collected in three locations within each invasion stage twice monthly throughout the reproductive season (March/May to July).ResultsIn both systems, reproductive investment was highest in the newly colonized area and decreased with time since colonization. A faster decrease in reproductive investment was found in the warmer, more productive system behind the invasion front, potentially associated with faster population growth and increased intraspecific competition. In both systems, individual variability in growth and reproductive traits increased from the newly colonized area to the areas of earlier colonization.Main conclusionsThe patterns observed in the two systems suggest a common invasion strategy independent of environmental conditions and highlight the dynamic nature of invasive populations’ life history behind the invasion front. Common energetic allocation strategies can be expected at the invasion front. Range expansion may be associated with population growth induced by rapid acclimation to biotic conditions associated with range shift.

How does oestradiol influence the AVT/IT system in female round gobies during different reproductive phases?

ABSTRACTIn this in vitro gradient perfusion study, we determined whether there is a functional relationship between oestradiol and the arginine vasotocin/isotocin (AVT/IT) system in the female round goby (Neogobius melanostomus). Brain explants were perfused in medium supplemented with 17β-oestradiol (E2) at doses mimicking the plasma levels of this hormone in nature during the spawning-capable phase and regressing phase. We aimed to establish which pathway, genomic or non-genomic, is involved in this mechanism in different reproductive phases. For this purpose, brain explants were perfused in medium supplemented with Fulvestrant (ICI 182.780) or Actinomycin D (Act D) separately or in combination with E2. The contents of AVT and IT in the perfusion media were determined using high-performance liquid chromatography (HPLC) with fluorescence and UV detection. During the spawning-capable phase, the effect of E2 on AVT release is mediated through oestrogen receptors (ERs) via both genomic and non-genomic pathways, while IT release is mediated through ERs via a genomic pathway only. In the regressing phase, release of both nonapeptides is mediated through ERs via a genomic pathway. This is the first study to present a feasible mechanism of oestradiol action on the AVT/IT system in female fish during different phases of the reproductive cycle.

Commentary: How Does Oestradiol Influence the AVT/IT System in Female Round Gobies During Different Reproductive Phases?

Teleostean neuropeptides such as arginine vasotocin (AVT) and isotocin (IT) and their homologues arginine vasopressin (AVP) and oxytocin (OT) are implicated in the regulation of reproduction and social behaviour in vertebrates

Fine scale spatio-temporal life history shifts in an invasive species at its expansion front

The dynamic shifts in life history traits by non-native populations at an invasion front may be driven by a combination of phenotypic plasticity and micro-evolutionary processes, allowing for appropriate responses to changes in biotic and abiotic factors associated with range expansion. The temporal and spatial scale at which these shifts occur, however, is largely unexplored. We examined the age-specific life-history responses of female round goby (Neogobius melanostomus) across a fine spatial scale by comparing traits of individuals at the expanding front of an invasive pathway with those of individuals living at the previous year’s front. Females in the new front were younger, exhibited higher body condition index and fecundity, and greater reproductive allocation than those living at the previous year’s front. No difference in back-calculated length at age or in seasonal growth increment was found between occupants of the old and new fronts. Age-specific differences in reproductive investment were observed; age-1 females from the new front exhibited greater reproductive effort but similar reproductive allocation, whereas age-2 females showed greater reproductive allocation in the new front, but similar reproductive effort. These age-specific differences may be related to differences in population density and other biotic factors encountered during ontogeny, or to micro-evolutionary processes. Our results demonstrate that fine scale changes in energy allocation towards reproduction through increases in reproductive allocation and fecundity occur at the invasion front, highlight how quickly those shifts can occur at the expansion front, and suggest that such changes in newly colonised areas facilitate range expansion.

Evaluating gonadosomatic index as an estimator of reproductive condition in the invasive round goby, Neogobius melanostomus

Using gonadosomatic index cut-off scores has become a standard protocol for selecting reproductive fish in studies on the reproductive biology of round goby, Neogobius melanostomus, a significant invader of the Laurentian Great Lakes, but the validity of this practice has not been validated with histological staging. The goal of the current study was to evaluate the effectiveness of using gonadosomatic index (GSI) cut-off scores to classify reproductive status in male and female round goby by documenting associations between GSI, sex steroids, and gonad development. Gonadal stage was determined in both sexes using hematoxylin and eosin histology. Plasma 11-ketotestosterone and testosterone were measured in males, and testosterone and 17β-estradiol were measured in females. Gonadosomatic index cut-off scores were effective in selecting spawning capable individuals at higher GSI values, but GSI values were limited in the ability to make further distinctions of gonadal stage and missed many spawning capable females. In females, testosterone levels were highest during vitellogenic growth and declined prior to ovulation. 17β-estradiol displayed a similar, but non-statistically significant pattern. Males with developing testes had higher levels of 11-ketotestosterone —but not testosterone —than reproductively immature males, although levels of these androgens were overall positively correlated in males. The findings indicate that the conventional GSI cut-off scores (1% in males, 8% in females) accurately assign spawning capable condition in both sexes; however, they may also exclude some spawning capable females with lower GSIs.

Finding round goby Neogobius melanostomus (Pallas, 1814) in the Rybinsk Reservoir

The data from finding a female round goby in June 2010 near the dam in the Central Reach of the Rybinsk Reservoir are presented. The presence of mature reproductive products may indicate the possibility of the successful acclimatization of this species in the Rybinsk Reservoir.

Response to putative round goby (Neogobius melanostomus) pheromones by centrarchid and percid fish species in the Laurentian Great Lakes

Pheromone trapping is an increasingly viable strategy to reduce invasive fish populations, largely due to the pheromones' function of evoking behavioral responses among conspecifics. Prior to attempting such population control techniques, the pheromones must be identified and their possible influences on non-target species addressed. The round goby (Neogobius melanostomus) is a species invasive to the Great Lakes region, and negatively impacts the ecosystem by interfering with local fish populations. At least two 5β-reduced 3α-hydroxyl steroids released by reproductive N. melanostomus (11-O-ETIO and 11-O-ETIO-3s) evoke olfactory sensory responses from the olfactory epithelium of conspecifics, and water conditioned by reproductive males (containing these steroids) attracts female round gobies. In this study, we examined whether these putative pheromones, along with simultaneously-released 11-O-ETIO-17s, stimulate olfactory sensory responses from alternative fish species sharing the same ecosystem as N. melanostomus in the Great Lakes region. Rock bass (Ambloplites rupestris), bluegill sunfish (Lepomis macrochirus), pumpkinseed sunfish (Lepomis gibbosus), smallmouth bass (Micropterus dolomieu), and yellow perch (Perca flavescens) were the targets of an electro-olfactogram experiment designed to record responses to odors. When compared to round goby responses from previous studies, amino acids and the bile acid consistently elicited electro-olfactogram responses across all species, but only round gobies showed a response to the putative pheromones. This study supports the concept of conducting a pheromone trapping trial in the field without adversely affecting the olfactory responses of non-target fish in the area.

Reproductive status influences multisensory integration responses in female round gobies, Neogobius melanostomus

Reproductive signalling often involves multimodal signals that are sent between conspecifics. While it is often easier to study one sensory modality at a time, examining multiple sensory modalities together may lead to a fuller understanding of how sensory signals are integrated under natural conditions. Often when integration occurs, behavioural responses are modified compared to those that occur in response to one sensory modality. We exposed female round gobies, Neogobius melanostomus , to a reproductive male's call and to extracts of water conditioned by a reproductive male (chemical stimulus) separately and simultaneously to examine differences between the females' unimodal and multimodal responses to male stimuli. We also tested females across the breeding season to examine effects of reproductive status on female responsiveness. Reproductive females were attracted to the unimodal stimuli, but when they were presented with multimodal stimuli, they spent significantly more time in the area of stimulus presentation than they did when they were presented with either stimulus alone. Nonreproductive females showed no enhancement of their response to multimodal stimulation and often failed to respond to any signals. Our results show that female gobies may cycle in their attraction and localization abilities to male stimuli throughout the breeding season and that reproductive females have a synergistic response to multimodal stimuli from reproductive males. ► We examined female round gobies' responses to unimodal and multimodal male stimuli. ► Reproductive status affected responsiveness to multisensory stimulation. ► Reproductive females increased responsiveness to male auditory and olfactory stimuli. ► Females that responded to multisensory stimuli also spent more time in the area of stimuli release. ► Nonreproductive females showed no response to male auditory and olfactory stimuli.

Laboratory and field evidence of sex-biased movement in the invasive round goby

Activity levels are modulated by trade-offs between reducing predation risk and the need to move in order to find food or mates. Because these trade-offs affect males and females differently, many species show sex- specific movement, dispersal patterns, and spatial naviga- tion capacities, with the sex that gains the most from territory ownership often dispersing less. Unlike mammals and birds, sex differences in movement among fishes remain poorly studied, and the connections between tests of movement propensity in the laboratory and in the field are rarely made. Here, we examine the differences in movement between male and female round goby (Neogobius melanostomus) in both laboratory and field settings. This fish species is invasive in North America and currently undergoing further range expansions. In the laboratory, round goby males were more active and explored a novel environment more readily than did females. A large-scale mark-recapture study in Lake Ontario over two years revealed that males moved more than females between years, but there were no within-year sex differences. Thus, round goby display male-biased movement patterns, providing a comparison point to dispersal patterns in other taxa. Understanding sex-specific movement of round goby in the field will also help predict dispersal and population dynamics, both in areas where round goby have already become established and where they are continuing to invade.

Reproductive female round gobies (Neogobius melanostomus) are attracted to visual male models at a nest rather than to olfactory stimuli in urine of reproductive males

AbstractFish are known to communicate in many ways and commonly use olfactory and visual signals. When round goby (Neogobius melanostomus) males become reproductive, they change from mottled grey to black and release sex steroids in their urine. In this study, we conducted a laboratory experiment to determine if reproductive female round gobies were attracted to a combination of olfactory (urine) and visual (silicone models) stimuli, representing reproductive and non-reproductive male round gobies. Females spent significantly more time at a nest with a black reproductive male model compared with a mottled non-reproductive male model. Neither urine type nor the interaction between model type and urine affected the time spent by reproductive females at a nest. Knowledge of the reproductive habits of the round goby may enable researchers to develop a method of species control for this invasive fish by manipulating its breeding habits.

Tracking bioaccumulation in aquatic organisms: A dynamic model integrating life history characteristics and environmental change

We have developed a dynamic model to track the evolution of contaminant concentration in an aquatic organism as a function of season and ontogeny throughout its life cycle. We have focused our analysis on the round goby ( Apollonia melanostoma), a globally distributed invasive forage fish. By integrating bioenergetics with a bioaccumulation model, we illustrate how life history characteristics interact to influence contaminant accumulation. We use uncertainty and sensitivity analyses to assess how the model output is affected by uncertainty and variability in model parameters. We then demonstrate the influence of important physiological characteristics on contaminant accumulation with two scenarios. First, we probe the influence of sexual dimorphism by comparing gender-specific accumulation of a standard polychlorinated biphenyl congener, PCB153, in male and female round gobies. We hypothesize that lipid loss in female gobies during spawning season leads to a decrease in the PCB body burden compared to male gobies. Second, we compare PCB accumulation in the round goby and in the mottled sculpin ( Cottus bairdi), the native forage fish that the round goby displaced in southern Lake Michigan, to determine whether the invasive species has an intrinsically different bioaccumulation potential than the native one. Our non-intuitive findings from these simulations illustrate how the interaction of growth rate with other life history characteristics lead to unexpected bioaccumulation patterns. The model we present is a flexible tool that integrates complex and dynamic interactions among environmental parameters, thus providing a means to better assess the potential for chemical accumulation in human and wildlife populations, and aiding the development of ecological forecasts.

Distribution, Abundance, and Range of the Round Goby, Apollina melanostoma, in the Duluth-Superior Harbor and St. Louis River Estuary, 1998–2004

Round gobies were first discovered in the Duluth-Superior Harbor, Lake Superior, in 1995. Anecdotal sightings by anglers and others suggested that the infestation was growing and expanding; however, direct evidence of the distribution and expansion rate in the harbor was largely unknown. Distribution and range of the round goby, Apollonia melanostoma, (formerly Neogobius melanostomus) was assessed using bottom trawl sampling throughout the Duluth-Superior Harbor, and portions of the lower St. Louis River from 1998 to 2004. Previous to 1998, round gobies only were reported to occupy the harbor between the two shipping entries (river kilometer 1 to 7). By 2004, they expanded throughout the harbor and upstream to river kilometer 13, but remained absent in western Lake Superior. The number of round gobies captured per 5 minutes of trawling (catch per unit effort, CPUE) increased from less than 1 fish in 1998 to an average 5.4 ± 1.2 SE fish in 2004, indicating a large increase in the population. The median yearly fish total length varied from 56.0 to 81.5 mm and wet weight varied from 2.3 to 7.0 g. As nest guarding male round gobies were located in rocky habitats inaccessible to trawling, the initial years were dominated by female round gobies with a 16:1 female to male ratio, but by 2002 the maximum ratio was 2:1. The ratio change may be indicative of the increasing population forcing males from their preferred rocky habitat onto open substrates that were more accessible to trawling.

Behavioural responses of female round gobies (Neogobius melanostomus) to putative steroidal pheromones

Although reproductive (RF) and non-reproductive (NRF) female round goby are attracted to washings of conspecific reproductive males and RF, respectively, behavioural responses of females to synthesized steroids has not been studied. We tested attraction and avoidance of RF and NRF to different blends of steroids previously shown to be either produced by reproductive males and/or detectable at a concentration of at least 10 –8 M by the olfactory epithelium of RF. Three blends of steroids were used, including: etiocholanolone (3 α -hydroxy-5 β -androstan-17-one), 11-oxo-etiocholanolone (3 α -hydroxy-5 β -androstane-11,17-dione), androstenedione, 11 β -hydroxy-androstenedione, and 11-ketotestosterone (‘free’ steroid blend); etiocholanolone glucuronide, etiocholanolone sulfate, 11-oxo-etiocholanolone glucuronide and 11-oxo-etiocholanolone sulfate (‘conjugated’ steroid blend); and all nine steroids together (‘total’ steroid blend). NRF were attracted to the free steroid blend and avoided the conjugated blend. RF did not reveal any significant bias to the steroid blends, but there was a tendency for RF to prefer conjugated steroids and avoid free steroids. Because there was no significant attraction by RF to particular blends of synthesized steroids tested, other compounds (sex attractants) not yet identified from the male round goby are likely responsible for initiating courtship and/or spawning behaviours in reproductive females.

Response of round gobies (Apollonia melanostomus) to fibreglass models of conspecifics

The round goby (Apollonia, formerly Neogobius, melanostomus) is an invasive fish that is currently a threat to the biodiversity of the Great Lakes. Mature individuals can vary in size from 70 mm to over 200 mm total length, and some males adopt black body coloration during the reproductive season. These variable characteristics as well as others suggest that sexual selection may be important in this species. Although previous work has been conducted on the role of body size in male-male interactions, this appears to be the first study that attempts to isolate the effects of body size and body coloration on intraspecific interactions in the round goby. A series of fibreglass models of round gobies that varied in size and coloration was used to assess the response of resident males and females to different intruders. Results of the model experiment suggested that body size plays an important role in interactions between male and female round gobies. However, body coloration appeared to have much less influence on round goby behaviour.

Does the reproductive status of male round gobies (Neogobius melanostomus) influence their response to conspecific odours?

While pheromone communication has been well documented in the female round goby, male responses have not been examined. We determined if male round gobies responded to odours of their conspecifics, and whether that response varied with their reproductive status (reproductive and non-reproductive). No significant differences were observed for any treatment (dechlorinated water, or water conditioned by reproductive males (RM) and non-reproductive males (NRM) and females), although RM spent more time inside shelter than NRM (p < 0.05). Morphologically, length and weight did not vary, but gonadosomatic index, seminal vesicle somatic index and relative head width did differ between the two male groups (p = 0.000). Round goby males guard nests in cavities, and so a preference for shelter with increasing reproductive status is expected. Also, a lack of male responses to conspecific odours may be adaptive in this species, since males nest together in high densities, where increased aggression might prove detrimental for nesting males.

Evidence of a Male Sex Pheromone in the Round Goby (Neogobius melanostomus)

The reproductive success of the round goby (Neogobius melanostomus), an invasive fish, may be mediated by the use of pheromones. We hypothesized that reproductive male (RM) round gobies release sex pheromone to which reproductive females (RF) respond. In this study, we compared behavioural and electrophysiological responses of reproductive and non-reproductive female round gobies to conspeci fic males. Results of behavioural experiments in the laboratory showed that RF spent significantly more time near the source of the male odour compared with odours from control water. However, RF did not distinguish between odours from non-reproductive male (non-RM) water and control water. Non-reproductive females (non-RF) were not attracted to odours released from RM or non-RM water. Results of electro-olfactogram (EOG) responses showed that both RF and non-RF discriminated between HPLC fractionated RM and non-RM odours. However, the EOG responses of RF were about eight-fold higher than non-RF exposed to RM odours. These findings confirm that RM round gobies release a pheromone signal that attracts RF. The results of this research may be useful in developing control strategy using natural pheromones to disrupt the reproductive behaviour of the invasive round goby and to curtail its effects on native species.

Behavioural responses of female Neogobius melanostomus to odours of conspecifics

The behavioural responses of reproductive and non‐reproductive female round gobies Neogobius melanostomus to water conditioned by reproductive and non‐reproductive males and females were tested. The behavioural responses of reproductive female round gobies exposed to odour of reproductive males included increased time spent near the source of the odour, elevated swimming velocities and directed movement to and around the odour source when compared with their responses to control water. These results suggested that pheromones released from reproductive males may induce spawning behaviour in reproductive females. Non‐reproductive females exposed to reproductive female odour spent significantly more time near the odour source of reproductive females compared with control water. Non‐reproductive females also showed directed movement towards and around the odour source when exposed to reproductive female odour. These results suggested that round gobies use inter‐sexual and intra‐sexual pheromones and that both sex and reproductive status are important in the detection and release of these pheromones.

Behavioural and electrophysiological responses by reproductive female Neogobius melanostomus to odours released by conspecific males

Behavioural and electrophysiological responses of reproductive and non‐reproductive female round gobies Neogobius melanostomus to water previously occupied by male round gobies (reproductive male water) were compared. Reproductive females spent more time than non‐reproductive females in a tank near the input of water conditioned from reproductive males. Also, reproductive females swam significantly faster than non‐reproductive females, suggesting that reproductive male odour may have activated spawning behaviour. Olfactory epithelial field potential measurement (electro‐olfactogram, EOG) showed that reproductive male water was a potent olfactory stimulus to reproductive females, but not to non‐reproductive females. Reproductive females responded significantly more than non‐reproductive females to solid‐phase (octadecylsilane) extracts of reproductive male water. Also, when these extracts were separated on reverse phase high performance liquid chromatography (HPLC), reproductive females showed noticeably greater responses than non‐reproductive females to the fractions that eluted between 30 and 40 min. The behavioural data support the hypothesis that reproductive male round gobies release compounds into the water that attract potential mates. The EOG data indicate that these compounds can be quantitatively extracted from the water and be partially purified by HPLC. The evidence is not sufficient to indicate whether or not the compounds are steroids. The relatively early elution time on HPLC, however, suggests that if these compounds are steroids, then it is more likely that they will be conjugated rather than free steroids.

The Round Goby ( Neogobius melanostomus) in Pennsylvania Tributary Streams of Lake Erie

The round goby ( Neogobius melanostomus) has successfully colonized the Great Lakes, where it appears to be out-competing and possibly displacing native fish species. Movement of the round goby into tributary streams of Lake Erie could further jeopardize native species. Sampling was done by electrofishing in six Pennsylvania tributary streams of Lake Erie from June 2000 through October 2001. Round gobies were collected from four of the six streams sampled: Elk Creek, Walnut Creek, Twentymile Creek, and Sixteenmile Creek. The most extensive colonization has occurred in Elk Creek where round gobies comprised 17.1% of the total number of fish where they were present, and occurred as far as 2.25 stream km upstream from the mouth of the creek. Round gobies fed almost exclusively on aquatic insects, and the most important insects in the diet were chironomid larvae. Female round gobies matured at 1+ years old. Individual fecundity ranged from 86 to 591 eggs, and increased with fish length. The plasticity of the diet, high fecundity, and aggressiveness of the round goby may make it a threat to native species in Pennsylvania tributary streams.

Fecundity and Reproductive Season of the Round GobyNeogobius melanostomusin the Upper Detroit River

Abstract The round goby Neogobius melanostomus successfully invaded the Great Lakes perhaps, in part, because of its reproductive strategy, whereby females spawn many times over an extended reproductive season. Female round gobies were collected from the upper Detroit River (by trawling and angling) during spring, summer, and fall of 1996 in order to determine fecundity patterns and length of the reproductive season. Female round gobies were mature at 1 year of age, which is 1 year earlier than has been noted for gobies in Europe. Gravid females were present in May and declined at the end of July, which indicates that spawning occurs from spring until midsummer. Mean fecundity was 198 eggs, and variation in fecundity was correlated with standard length (r 2 = 0.76, P < 0.0001) of females. Fecundity was lower than that observed for the same species in Europe, but it was generally higher than that of most native species with which gobies would compete. A field experiment showed that artificial nests contain...