Food,fights, and burrows: The adaptive significance of intraspecific aggression in the bay goby (Pisces: Gobiidae)

Summary The effects of size, sex, bout initiation, past experience, and prior residence were examined with respect to the outcome of intraspecific agonistic contests in the bay goby (Lepidogobius lepidus). In addition, the adaptive significance of this behavior was examined by investigating the relationship between dominance and access to two potentially limiting resources; food and the burrows of invertebrate symbionts.For heterosexual and male homosexual contests, size and initiation significantly affected bout outcome. Gender did not affect heterosexual encounters. In female homosexual bouts initiation played a significant role in determining contest outcome while size did not. Both past experience and prior residency had significant effects on the outcome of intraspecific encounters.Dominant gobies had increased access to simulated invertebrate burrows and limited food. It appears that intraspecific aggression is an adaptive phenomenon through which access to limiting resources may be mediated.Portions of this research were completed during my stay as a visiting scientist at the National Marine Fisheries Service, Southwest Fisheries Center, Tiburon, CA     

Diet and food selection in the endemic Hawaiian amphidromous goby, Sicyopterus stimpsoni (Pisces: Gobiidae)

Synopsis The ecological role of Sicyopterus stimpsoni as a nearly exclusive algal grazer in Hawaiian streams is established through gut content analysis of 192 fish from Wainiha River on the northern island of Kaua'i. Algae in three phyla (Chlorophyta, Cyanophyta, and Chrysophyta) were found to be the primary components of the fish's diet (94.62% of dry biomass). Aquatic insect immatures (primarily Chironomidae) accounted for most of the remaining food biomass (5.37%). Poorly developed gill rakers and high gut-to-length ratios provide evidence for adaptation to herbivory and morphological separation of S. stimpsoni from sympatric gobiods. Interspecific competition for the green alga, Cladophora sp., is suggested as an important feature of biotic interactions among native stream fishes but is mitigated by interspecific differences in food preference and utilization. A Category V hurricane which devastated the island in September 1992 provided a fortuitous opportunity to study disturbance influences on benthic food resources in the stream. Disturbance regimes influenced food selection of S. stimpsoni by altering the abundance and composition of stream algae. Rapid adjustment of S. stimpsoni to changes occurring in algal resource abundance illustrates its superb adaptation to life in a swift-water environment subjected to periodic flood-induced disturbance.     

An electrophoretic study of the systematic relationships of some closely related goby species (Pisces, Gobiidae)

An electrophoretic study of genetic variation at 31 loci in each of nine closely related gobiid species was carried out in order to assess their systematic relationships. The species used were: Pomatoschistus canestrinii, P. lozanoi, P. marmoratus, P. microps, P. minutus, P. norvegkus, P. pictus, Knipowitschia caucasica, Neogobius melanostomus. Genetic distances ( D ) and identities ( I ) were calculated by Nei's method for all 36 pairwise comparisons and dendrograms were constructed.
The results show that the very similar and cross-fertile species pair, P. lozanoi and P. minutus , have the highest I value; P. norvegkus has high I values with both species. Pomatoschistus marmoratus and P. microps also display high genetic similarity with each other. The remaining Pomatoschistus species and Knipowitschia caucasica are broadly and moderately equidistant from each other and from the five species refferred to above, while Neogobius melanostomus is considerably more distant from all other species.
These findings essentially agree with the pattern of relationships established using classical taxonomic approaches. However, the observation that Knipowitschia caucasica is as similar to Pomatoschistus spp. as the latter are to each other suggests that the generic distinction of Knipowitschia could usefully be reconsidered.     

Ventilation rate and behavioural responses of two species of intertidal goby (Pisces: Gobiidae) at extremes of environmental temperature

We investigated the behavioural responses of two gobiid fish species to temperature to determine if differences in behaviour and ventilation rate might explain any apparent vertical zonation. A survey of the shore at Manly, Moreton Bay revealed Favonigobius exquisitus to dominate the lower shore and Pseudogobius sp.4 the upper shore. These species were exposed to a range of temperatures (15–40°C) in aquaria for up to 6 h. At 20 °C F. exquisitus exhibited a mean gill ventilation rate of 26 ± 1.4 bpm (beats per minute) differing significantly from Pseudogobius, which ventilated at a fivefold greater rate of 143 ± 6 bpm. The ventilation rate in F. exquisitus underwent a fivefold increase from normal local water temperature (20 °C) to high temperature (35 °C) conditions, whereas that of Pseudogobius did not even double, suggesting that Pseudogobius sp. is a better thermal regulator than F. exquisitus.While both species emerged from the water at high temperatures (>30 °C) the behaviours they exhibited while immersed at high temperature were quite different. F. exquisitus undertook vertical displacement movements we interpret as an avoidance response, whereas Pseudogobius sp. appeared to use a coping strategy involving movements that might renew the water mass adjacent to its body. The thermal tolerances and behaviours of F. exquisitus and Pseudogobius sp. are in broad agreement with their vertical distribution on the shore.     

The influence of colony size and coral health on the occupation of coral-associated gobies (Pisces: Gobiidae)

Fishes of the genus Gobiodon are habitat specialists by their association with Acropora corals. Little is known about the parameters that define host coral quality for these fishes, in particular their breeding pairs. Data were collected in the northern Red Sea using 10 × 1-m belt transects in different reefs and zones. Gobiid density was highly correlated with coral density over all sites and zones, and the more specialized goby species preferred coral species that are less vulnerable to environmental stress. Moreover, the occupation rate of corals by goby breeding pairs significantly increased with colony size and decreased with partial mortality of colonies. Logistic regression showed that both coral size (being most important) and partial mortality are key factors influencing the occupation by breeding pairs. This study provides the first evidence that breeding pairs of coral-associated gobiids have more advanced habitat requirements than con-specifics in other social states. As coral reefs are threatened worldwide and habitat loss and degradation increase, this information will help predict the potential effects on those reef fishes obligatorily associated with live corals.     

Trophic specialization in Arctic charr Salvelinus alpinus (Pisces; Salmonidae): morphological divergence and ontogenetic niche shifts

Lake Thingvallavatn supports four trophic morphs of Arctic charr, Salvelinus alpinus (L.); two of the morphs are benthic (small and large benthivorous charr) one exploits pelagic waters (planktivorous charr) and the fourth is found in both habitats (piscivorous charr). The morphological variation among these morphs was analysed by use of principal component analysis and canonical discriminant analysis. The benihic morphs have a short lower jaw and long pectoral fins. The benthic fish also have fewer gillrakers than the other morphs. Small and large benthivorous charrs attain sexual maturity from 2 and 6 years of age, and at fork lengths from 7 and 22 cm, respectively. Small benthivorous charr retain their juvenile parr marks as adults, have beige ventral colours, and are frequently melanized under the lower jaw. Planktivorous and piscivorous charr attain sexual maturity from 4 and 6 years of age, from fork lengths of 15 and 23 cm, respectively. This phenotypic polymorphism is associated with habitat utilization and diet of the fish, and has probably arisen within the lake system through diversification and niche specialization. The pelagic morphs apparently stem from a single population, and are possibly diversified through conditional niche shifts which affect ontogeny. Juveniles reaching a body length of 23 cm may change from zooplankton to fish feeding. Asymptotic length increases thereby from 20.5 cm in planktivorous charr to 30.2 cm in piscivorous charr. The benthic morphs appear to represent separate populations, although both feed chiefly on the gastropod Lymnaea peregra. Their co-existence seems to be facilitated by size dependent constraints on habitat use. The small morph (asymptotic length 13.3 cm) exploit the interstitial crevices in the lava block substratum, whereas the large morph (asymptotic length 55.4 cm) live epibenthically.     

Big is better: the importance of size for reproductive success in male Pomatoschistus minutus (Pallas) (Pisces, Gobiidae)

The sand goby, Pomatoschistus minutus , was used in aquarium experiments to study the importance of body size for the ability of males to gain access to nest sites and mates. When several male and female P. minutus were allowed to reproduce together, on average, half of the males built nests, and half of those males obtained eggs in their nests. Males with nests were significantly larger than males without nests, and nests with eggs belonged to males larger than the males with empty nests. In another experiment, when two males were competing for one nest, the largest male occupied the nest when both fish were put into the aquarium simultaneously. However, when the smaller male had been allowed to establish a nest before the larger male was introduced, the small male could usually retain the nest. Males with a body length < 50 mm did not build nests at all in the early part of the breeding season. In female choice experiments, no preference for larger males was found. Thus, male-male competition for nest sites and behavioural differences between different sized males seem to be the main factors influencing the non-random mating success in male P. minutus.     

A new marine goby of genus Callogobius (Teleostei: Gobiidae) from Taiwan

A new marine goby Callogobius sheni collected from coral reefs off southern Taiwan is described. The new species can be distinguished from congeneric species by the following combination of features: dorsal fin rays VI-I, 9; anal fin rays I, 7; pectoral fin rays 18; longitudinal scale rows 27–28; predorsal scale rows 9–10; no posterior oculoscapular and preopercular canals; body pale white with five blackish brown cross bands; caudal and pectoral fins each with a large blackish brown blotch.     

Feeding ecology of the Bay Goby (Pisces: Gobiidae). Effects of behavioral,ontogenetic, and temporal variation on diet

The ontogenetic, diel, seasonal, and yearly variations in gut fullness, diet, and prey diversity for a California estuarine gobiid (Lepidogobius lepidus Girard) were examined. Also the feeding behavior of this species was described.Small (<50 mm, SL) and large (? 50 mm, SL) gobies consumed similar prey types in different proportions. Major prey items were polychaetes, harpacticoid copepods, gammarid amphipods, molluscs, and other crustaceans. Diets of large and small gobies were not significantly correlated, and larger fish had a more diverse diet. Small fish fed at all times while larger gobies fed primarily at night. Changes in diet may be related to differential prey preferences, feeding chronologies, and increases in fish size.Both large and small gobies displayed seasonal differences in diet and prey diversity. Year-to-year changes in diet also were noted for both size classes. The bay goby uses different feeding behaviors to capture sedentary and motile prey and appears to forage opportunistically. This behavior is probably advantageous in an environment which fluctuates drastically.     

A new microsporidian infecting the musculature of the endangered tidewater goby (Gobiidae)

A previously unrecognized microsporidian (Kabatana newberryi n. sp.) is described from the musculature of Eucyclogobius newberryi (Gobiidae) in Big Lagoon, Humboldt County, California. Spores are ovoid, ranging in size from 2.8 +/- 0.3 microm in total length and 1.9 +/- 0.4 microm in width (measurements of 30 spores made by calculation from micrograph). The polar filament has 9-10 coils in 1-2 rows. Development occurs in direct contact with host muscle cell cytoplasm, without xenoma or sporophorous vesicle. Phylogenetic analysis of the new species and of 35 other microsporidians known to infect fish using 1115 base pairs of aligned 16S rRNA gene indicate the new species is most closely related to Kabatana takedai. However, the new species differs by 11% sequence divergence from K. takedai. Divergence in morphology and genetic data allow for diagnosis from all other fish-infecting microsporidia and supports recognition of a new species of microsporidian, Kabatana newberryi n. sp., presently known only from a suspected specific host, the endangered tidewater goby Eucyclogobius newberryi.     

Occurrence of vertebral deformities in Gobiidae (Pisces) from the Tagus estuary

In four species of gobiid fish caught in Tagus estuary during 1996, the incidence of skeletal deformities ranged from 2 to 5%. Differences between sampling stations or between the two most abundant species Pomatoschistus minutus and Gobius niger were statistically not significant (p > 0.05). The type of deformity depended upon species. P. minutus and P. microps showed bone nodules at the inferior side of the abdominal vertebrae, whilst G. niger and G. paganellus had shortened caudal vertebrae (achondroplasia) and deformed ural plates. The possible role of pollution or other conditions in the Tagus estuary is discussed.     

Coexistence of predator and prey in intraguild predation systems with ontogenetic niche shifts

In basic intraguild predation (IGP) systems, predators and prey also compete for a shared resource. Theory predicts that persistence of these systems is possible when intraguild prey is superior in competition and productivity is not too high. IGP often results from ontogenetic niche shifts, in which the diet of intraguild predators changes as a result of growth in body size (life-history omnivory). As a juvenile, a life-history omnivore competes with the species that becomes its prey later in life. Competition can hence limit growth of young predators, while adult predators can suppress consumers and therewith neutralize negative effects of competition. We formulate and analyze a stage-structured model that captures both basic IGP and life-history omnivory. The model predicts increasing coexistence of predators and consumers when resource use of stage-structured predators becomes more stage specific. This coexistence depends on adult predators requiring consumer biomass for reproduction and is less likely when consumers outcompete juvenile predators, in contrast to basic IGP. Therefore, coexistence occurs when predation structures the community and competition is negligible. Consequently, equilibrium patterns over productivity resemble those of three-species food chains. Life-history omnivory thus provides a mechanism that allows intraguild predators and prey to coexist over a wide range of resource productivity.     

Demographic characteristics of an intertidal bay goby (Lepidogobius lepidus)

Synopsis In a fourteen month study (May 1976 – June 1977) I examined the following characteristics of an intertidal bay goby (Lepidogobius lepidus) in Morro Bay, California, U.S.A.: annual and seasonal patterns of abundance, age composition and growth rates, survivorship and mortality patterns, and the reproductive cycle for female gobies. Fishes were collected with the aid of quinaldine and otoliths and ovaries removed. Age and growth rates were estimated from otolith annuli using a back calculation formula and a Brody-Bertalanffy growth curve. Mortality rates were derived using the methods of Heincke (1913), Robson & Chapman (1960), mean age, and a catch curve (Ricker 1975). A gonad index was used to describe the annual reproductive cycle. Results indicated that abundance fluctuated seasonally and that these fluctuations appeared to be caused by reproductive emigrations. Bay gobies reached an age of 7+ and a standard length of 87 mm. Growth was relatively constant (6 mm yr⁻¹) until age 5, at which point it began to decline. The mean rates of survivorship, mortality, and instantaneous mortality were 0.75, 0.25, and 0.29 respectively. Mortality rates for individual age classes ranged from 0.13 to 0.51 and increased with age. This stock appears to reproduce mainly during the winter.     

The biology of the burrowing goby Croilia mossambica Smith (Teleostei,Gobiidae)

Synopsis Croilia mossambica, a burrowing goby endemic to the coastal lakes of south east Africa occurs from L. Poelela (salinity 8%.) to L. Sibaya (freshwater). Since these lakes are isolated from one another its distribution is discontinuous. It is not found in estuaries or the sea. In L. Sibaya C. mossambica is present on sheltered sides from a depth of 1 m to about 16 m. On exposed shores it is not found at less than 3.5 m depth. It is restricted to sandy, quiet water areas and is unable to form burrows where the substrate is disturbed by water movement, is muddy or consists of sand with a particle diameter greater than 0.5 mm. The maximum depth at which it lives is probably determined by light penetration since it is dependent on sight for prey capture. The food consists of slow moving benthic invertebrates such as chironomid larvae, gastropods, bivalves and amphipods. The relative importance of each depends upon its abundance. C. mossambica is a summer breeder with a protracted spawning season. The sticky eggs measure 0.7–0.8 mm when laid. Tolerance experiments show that it is euryhaline and can survive in seawater of 35%. and that its upper temperature limit is between 32 and 35°C. Temperatures in shallow waters of lakes and estuaries of the region frequently exceed 35°C. Thus its local distribution may be limited by temperature. Its lack of tolerance to high temperatures, to marked water movements and its ability to live in seawater indicates that C. mossambica is suited to life in the sea rather than in estuaries. It is suggested that it was present in quiet areas of the sea, such as lagoons, and that it invaded the coastal lakes which were formed as the estuaries and river valleys were inundated during the Pleistocene marine transgression. C. mossambica cannot tolerate estuarine conditions and with the present absence of quiet water in the sea off the south east African coast the species is now confined to deep coastal lakes.Note     

Effects of prey size and foraging mode on the ontogenetic change in feeding niche ofColostethus stepheni (Anura: Dendrobatidae)

The feeding niche ofColostethus stepheni changes during ontogeny. Small individuals eat small arthropods, principally mites and collembolans, and larger frogs eat bigger prey of other types. The shift in prey types is not a passive effect of selection for bigger prey. There is a strong relationship between electivity for prey types and frog size, independent of electivity for prey size. Four indices of general activity during foraging (number of movements, velocity, total area utilized and time spent moving), which are associated with electivity for prey types in adult frogs and lizards, did not predict the ontogenetic change in the diet ofC. stepheni. Apparently, the behavioral changes that cause the ontogenetic change inC. stepheni are more subtle than shifts in general activity during foraging. Studies of niche partitioning in communities of anurans that do not take into consideration ontogenetic changes in diet and seasonal changes in the size structures of populations present a partial and possibly erroneous picture of the potential interactions among species.     

Complete mitochondrial genome of the Walking goby Scartelaos histophorus (Perceformes, Gobiidae)

The Walking goby Scartelaos histophorus (Perciformes, Gobiidae) is an amphibious gobioid fish. In this paper, the complete mitochondrial genome of S. histophorus was first determined. The genome is 16,496 bp in length and consists of 13 protein-coding genes, 22 tRNA genes, 2 ribosomal RNA genes, and 1 control region. The overall base composition of S. histophorus is 27.5% for T, 28.0% for C, 28.3% for A, and 16.1% for G, with a slight A+T bias of 55.8%. It has the typical vertebrate mitochondrial gene arrangement.     

Stomach fullness modulates prey size choice in the frillfin goby,Bathygobius soporator

Behaviours related to foraging and feeding in predator–prey systems are fundamental to our understanding of food webs. From the perspective of a predator, the selection of prey size depends upon a number of factors including prey vulnerability, prey size, and the predator's motivation to eat. Thus, feeding motivation and prey visual cues are supposed to influence predator decisions and it is predicted that prey selection by visual cues is modulated by the predator's stomach fullness prior to attacking a prey. This study was conducted using an animal model from the rocky shores ecosystem, a predatory fish, the frillfin goby Bathygobius soporator, and a benthic prey, the mottled shore crab Pachygrapsus transversus. Our results demonstrate that frillfin gobies are capable of visually evaluating prey size and that the size evaluation process is modulated by the level of stomach fullness. Predators with an empty stomach (0% fullness) attacked prey that was larger than the predicted optimal size. Partially satiated predators (50% stomach fullness) selected prey close to the optimal size, while fully satiated predators (100% stomach fullness) showed no preference for size. This finding indicates an integrative response of the predator that depends on the input of both internal and external sensory information when choosing prey. Predator perceptions of visual cues (prey size) and stomach fullness modulate foraging decisions. As a result, a flexible feeding behaviour emerges, evidencing a clearly adaptive response in line with optimal foraging theory predictions.     

A new goby, Glossogobius minutus (Teleostei: Gobiidae) from the south-west coast of India

A new species of gobiid fish Glossogobius minutus collected from the south-west coast of India is described. The morphological, morphometric and meristic characters were studied with special emphasis on osteology. The various characters are compared with those of G. giuris (Harn.) and G. biocellatus (Val.), the only other species of the genus reported from this region. Glossogobius minutus is a benthic omnivore and shows distinct sexual dimorphism.