Juvenile Fish Species Research Articles

Visual characteristics of three species of juvenile salmonid fish and their homing migration

Visual characteristics of three species of juvenile salmonid fish and their homing migration

Visual characteristics of three species of juvenile salmonid fish and their homing migration

Visual characteristics of three species of juvenile salmonid fish and their homing migration

Different Surrounding Landscapes may Result in Different Fish Assemblages in East African Seagrass Beds

Few studies have considered how seagrass fish assemblages are influenced by surrounding habitats. This information is needed for a better understanding of the connectivity between tropical coastal ecosystems. To study the effects of surrounding habitats on the composition, diversity and densities of coral reef fish species on seagrass beds, underwater visual census surveys were carried out in two seagrass habitat types at various locations along the coast of Zanzibar (Tanzania) in the western Indian Ocean. Fish assemblages of seagrass beds in a marine embayment with large areas of mangroves (bay seagrasses) situated 9 km away from coral reefs were compared with those of seagrass beds situated on the continental shelf adjacent to coral reefs (reef seagrasses). No differences in total fish density, total species richness or total juvenile fish density and species richness were observed between the two seagrass habitat types. However, at species level, nine species showed significantly higher densities in bay seagrasses, while eight other species showed significantly higher densities in reef seagrasses. Another four species were exclusively observed in bay seagrasses. Since seagrass complexity could not be related to these differences, it is suggested that the arrangement of seagrass beds in the surrounding landscape (i.e. the arrangement on the continental shelf adjacent to the coral reef, or the arrangement in an embayment with mangroves situated away from reefs) has a possible effect on the occurrence of various reef-associated fish species on seagrass beds. Fish migration from or to the seagrass beds and recruitment and settlement patterns of larvae possibly explain these observations. Juvenile fish densities were similar in the two types of seagrass habitats indicating that seagrass beds adjacent to coral reefs also function as important juvenile habitats, even though they may be subject to higher levels of predation. On the contrary, the density and species richness of adult fish was significantly higher on reef seagrasses than on bay seagrasses, indicating that proximity to the coral reef increases density of adult fish on reef seagrasses, and/or that ontogenetic shifts to the reef may reduce adult density on bay seagrasses.

Food ingestion in juvenile cod estimated by inert lanthanide markers – effects of food particle size

AbstractDevelopment of formulated starter diets and improvement of diets for juvenile marine fish species are major challenges in aquaculture. The ingestion rate may be regarded as a parameter for evaluating whether a diet particle is available, recognized, of adequate size, palatable, and preferred by small fish. In this study, we evaluated the effect of food particle size (150–3425 μm) on ingestion rate in juvenile cod (36–826 mg wet weight). Lanthanide oxides were used as markers. Several mixtures of lanthanide marker-labelled diets were produced by combination of the mono-labelled size classes. Each combination was fed for one, four, or seven days to groups of juvenile cod in separate tanks. After termination by anaesthetic, the fish were collected, individually weighed, and frozen until analysis. The amount of lanthanides in the homogenized fish was measured by inductively coupled plasma-mass spectrometry (ICP-MS). There were no significant differences in ingestion of any of the markers when given in a mixture of mono-labelled particles. Thus, the markers Y2O3, La2O3, Nd2O3, Dy2O3, and Yb2O3 may be used as inert tools for evaluating diet ingestion. The total intake of dry diet was about 13 mg g−1 body weight. The particle size that caused the highest food intake was less than 1.2 mm in all experiments.

Delaware Bay salt marsh restoration: Mitigation for a power plant cooling water system in New Jersey, USA

In 1994 Public Service Electric and Gas of New Jersey (PSE&G), now Public Service Enterprise Group (PSEG), proposed and implemented a program to offset egg, larvae and fish losses at the cooling water intake at Salem Generating Station. The program included wetland habitat restoration, fish ladder installation, new cooling water intake technology, and a biological monitoring program. The wetland habitat restoration was the core component and the most controversial aspect of the program. It addressed two types of habitats: diked salt hay farms and wetlands dominated by Phragmites australis. The wetland restoration program used ecological engineering principles to restore approximately 4550 ha. It also protected upland buffers and other lands for a total of over 8700 ha. Eight fish ladders were installed to allow anadromous river herring to return to previously blocked spawning habitat. PSEG also implemented operational changes, installed advanced cooling water intake technology to reduce losses of invertebrates and early life stages of fish, and conducted studies of behavioral deterrents. The biological monitoring program continues to assess the abundance and distribution of juvenile coastal migratory fish species while they are in the Delaware River Estuary; it also monitors use of wetlands by fish and invertebrates.

Fishery practice versus experimental design: Preliminary results of the introduction of protective sieves in the eel fyke-net fishery of the Vistula Lagoon, Poland

In response to the high by-catch of juvenile commercial fish species in fyke-nets used in targeted eel catches in the Vistula Lagoon, a regulation came into force requiring gear to be fitted with protective sieves with openings 20 mm × 65 mm in diameter. The protective sieves replace material with 16 mm mesh bar lengths in the codend. This paper presents the quantitative composition and length distribution of fish from commercial catches prior to and following the obligatory mounting of sieves in the gear (1999) as well as after they had come into widespread use (2004). The application of the sieves limited the retention of juvenile bream, perch, and roach. They also significantly limited the numbers of fish of the smallest length classes that were retained. The total number of pikeperch retained in the fyke-net was reduced, although the length distribution of this species did not vary as much as it did with other species. A difference in the protection effect was noted in the catches from the current study in comparison with experimental catches conducted in the same month in 1998–1999. Selectivity curves for pikeperch and bream were calculated based on samples collected with gear fitted with protective sieves accompanied by an additional net sewn to the outside of the sieve to retain all the fish that passed through the fyke-nets. L50% was 17.6 and 12.4 cm TL, respectively. In the commercial catches made in 2004, only a slight limitation in the retention of pikeperch of the 11–14 cm length class was noted, and bream specimens smaller than 17 cm TL were all but eliminated. The authors are of the opinion that behavior and factors that affect mortality following contact with the fishing gear are significant. The variability of bream regarding the dependence of body height on length might have influenced the results.

Effects of Zn pre-exposure on Cd and Zn bioaccumulation and metallothionein levels in two species of marine fish

Zinc is an essential trace metal but also a potential toxicant to aquatic organisms. In this study, two juvenile marine fish species, the black sea bream Acanthopagrus schlegeli and the grunt Teraponjarbua, were pre-exposed to Zn either from waterborne (0.74–170 μg L −1) or dietary (39–5926 μg g −1) Zn for 1 or 3 weeks. The concentrations of Zn and metallothionein (MT) in the whole body of the black sea bream and in the gills, viscera and carcass of the grunt were then measured during this pre-exposure. Following the pre-exposure, both fish species were then exposed to 109Cd and 65Zn labeled food or water to quantify the dietary assimilation efficiency (AE) and the uptake rate of dissolved Cd and Zn. Zn concentrations in both fish species were enhanced after pre-exposure, but the increases were much less than the increase of ambient Zn pre-exposure concentration. Following Zn pre-exposure, MT concentrations in the viscera and carcass were significantly elevated, whereas the MT levels were not significantly elevated in the gills. Waterborne and dietary Zn exposure enhanced the uptake rates of dissolved Cd and Zn in both fish. The maximum increases of uptake rate constants of dissolved Cd and Zn were up to 1.9–2.8 and 2.1–2.6 times, respectively, in the seabream and grunt. In contrast, dietary assimilation efficiency of Cd and Zn was not significantly enhanced following Zn pre-exposure. A positive linear relationship was found between the uptake rate constants of dissolved metals and Zn or MT concentrations in the fish. The results suggested that Zn pre-exposure increased the potential of metal uptake from ambient water, but had little effect on dietary metal uptake. Furthermore, the Zn body concentration and metal uptake from the dissolved phase were significantly dependent on the fish body size.

New tetrachromic VOF stain (Type III-G.S) for normal and pathological fish tissues.

A new VOF Type III-G.S stain was applied to histological sections of different organs and tissues of healthy and pathological larvae, juvenile and adult fish species (Solea senegalensis; Sparus aurata; Diplodus sargo; Pagrus auriga; Argyrosomus regius and Halobatrachus didactylus). In comparison to the original Gutiérrez VOF stain, more acid dyes of contrasting colours and polychromatic/metachromatic properties were incorporated as essential constituents of the tetrachromic VOF stain. This facilitates the selective staining of different basic tissues and improves the morphological analysis of histochemical approaches of the cell components. The VOF Type III -6.5 stain is composed of a mixture of several dyes of varying size and molecular weight (Orange G<acid Fuchsin<Light green<Methyl Blue<Fast Green), which are used simultaneously, and it enables the individual tissues to be selectively differentiated and stained. Muscle fibers, collagen, reticulin and elastin fibers, erythrocytes, cartilage, bone, mucous cells, oocytes and larvae were selectively stained and differentiated. Dyes with small size and molecular weight (i.e Orange G), penetrate all tissue structures rapidly, but are only tightly retained in densely textured tissues (i.e erythrocytes). Methyl Blue is an interesting triarylmethane dye (large size and molecular weight), which is incorporated in this new VOF tetrachrome stain, and acquires histochemical significance when used at acid pH (2.8) because collagen and reticulin fibers, as well basophilic and metachromatic substances (strongly ionized sulphated glycoconjugates) can be identified. Muscle tissues show an evident green colour (Fast Green or Light Green affinities), even those isolated and/or diffuse muscle fibers present in the digestive submucosa layer. Connective tissues showed a specific and strong blue colour (Methyl Blue affinity) or mixed blue-red staining (Methyl Blue and Acid Fucshin affinities). Very noticeable is the staining of the mucous cells, as well as the hyaline capsule of the viral lymphocystic cells, which were stained blue-purple (carboxylated and/or strongly ionized sulphated groups). Cartilaginous tissues showed a blue or purple (Methyl Blue affinity) staining, and a specific red colour (Acid Fucshin affinity) was evident during calcification or in bone structures (i.e skeleton, fins, gills, teeth).

Diel shifts in community composition and feeding of juvenile fishes in the pelagic area of a large shallow lake

Diel cycles of changing ambient illumination have been shown to have strong influence on fish community composition in freshwater systems, mainly due to diel habitat shifts of fish between sheltered and more exposed, but profitable sites. Low information is available, however, from diel patterns of fish community composition and feeding in the central areas of large shallow lakes where lake depth and diameter may hamper diel migrations. We studied whether there are diel differences in species abundance and shifts in feeding modes of the juvenile pelagic fish species over an 8 months sampling period in a shallow lake. The strong decline of perch numbers towards the night suggests low nocturnal activity for this species. In contrast, the nearly constant numbers of roach over the full diel cycle points to pronounced activity under changing light intensities. Increased ruffe numbers at night reflect the good adaptation of this species to feed efficiently at low light intensities. Niche segregation of fish species along the diet axis was low. There was low evidence that diel shifts in the fish community composition were attributed to diel horizontal migrations of species into or out of the pelagic zone. Because availability of preferred zooplanktonic prey was high, differential diel activity patterns of species reflect their genetically fixed, albeit varying adaptations to feed under low-light conditions, instead of being an active avoidance to reduce competition.

Abundance and distribution of larval and juvenile fish in Coos Bay, Oregon: time-series analysis based on light-trap collections

Recent interest in the role of estuaries as 'essential fish habitat' has led to more precise definitions and quantitative assessments of estuaries as nursery habitat. Although the larvae and juveniles of >20 fish species are found in Pacific Northwest estuaries, information on their presence in and use of Oregon's estuaries is scarce. The objectives of this study were to use a long-term time series (3.75 yr) of high-frequency (every 1-2 d) light-trap collections from Coos Bay, Oregon to doc- ument species diversity, compare intra- and interannual patterns of species abundance and size, and identify potential wind- and/or tidally-driven transport mechanisms. Thirty-five taxa (28 species) of larval and juvenile fish were identified. Five species consistently comprised >70% of the catch. On average, the majority (94 ± 6% SD) of the catch at the most ocean-dominated site occurred during the downwelling season (1 October to 31 May) with 15 to 62% of that catch collected during the spring transition (1 April to 31 May) when conditions shift from predominantly downwelling to upwelling conditions. Conversely, <1 km farther up estuary an average of 64 ± 12.7% SD of the catch occurred during downwelling conditions with only 8% during the spring transition. Relative abundance patterns indicate seasonal and spatial variation in estuarine use and potentially extended residence periods for some species. Time-series analyses indicate the presence of the larval and juvenile fish collected in the estuary may have been primarily regulated by a combination of tidally-driven trans- port and reproductive timing with less evidence for wind-driven transport.

Relative importance of interlinked mangroves and seagrass beds as feeding habitats for juvenile reef fish on a Caribbean island

Mangroves and seagrass beds are important daytime shelter habitats for juvenile Caribbean reef fish species, but little is known about their relative importance as feeding grounds. In the present study, we tested the degree to which these 2 habitats are used as a feeding ground for 4 nocturnally active fish species on Curacao, Netherlands Antilles. Stable isotope analysis was used as a technique to distinguish between feeding in mangroves and seagrass beds. Individuals of the 4 species which were sheltering during the daytime in permanently inundated fringing mangroves subject to low tidal exchange showed a stable carbon isotope signature indicative of a mixed diet composed of crustaceans from mangroves as well as seagrass beds, with the contribution from mangrove food items lying between 57 and 92%. However, individuals of the same species sheltering on adjacent (<50 m distance) seagrass beds during the daytime showed a carbon signature indicative of almost exclusive feeding on seagrass beds. This indicates that 2 different subpopulations probably exist for the 4 species studied: a population of fishes sheltering in mangroves during the daytime and feeding primarily in the mangroves and secondarily in the seagrass beds at night, and a population of fishes of the same species sheltering in adjacent seagrass beds during the daytime and feeding primarily in seagrass beds at night.

The selective properties of some sieve nets

By-catch and discarding of juvenile fish species in the brown shrimp ( Crangon crangon) fishery is a well-recognised problem. Sieve nets have recently been introduced as a mandatory technical measure to reduce this by-catch under EC Council regulations. Four different designs of sieve nets were developed and tested in UK waters and compared for their selective properties. The question of efficiency in capture and loss of the target species was also assessed. Three species of fish were measured in the standard gear and the experimental gear to determine selectivity ogives. Only few fish were observed in the majority of the hauls and it was therefore not possible to use standard analysis techniques to obtain release-curves by individual hauls. The paper demonstrates the selective properties of the sieve nets as determined by the use of bootstrapping techniques in combination with the SELECT model. The potential for a reduction in benthic impact resulting from sieve net usage is also discussed.

Utilization of the exotic cladoceran Daphnia lumholtzi by juvenile fishes in an Illinois River floodplain lake

Daphnia lumholtzi comprises a substantial component of the zooplankton community during mid‐ to late‐summer in Lake Chautauqua, a floodplain lake along the Illinois River near Havana, Illinois. In order to quantify the utilization of D. lumholtzi by juvenile fishes, diet analyses were conducted for seven juvenile fish species collected from Lake Chautauqua during the 2001 annual drawdown period. Freshwater drum Aplodinotus grunniens and emerald shiner Notropis atherinoides demonstrated negative selectivity for D. lumholtzi relative to native zooplankton species whereas four species of fish (bluegill Lepomis macrochirus, white bass Morone chrysops, white crappie Pomoxis annularis and black crappie Pomoxis nigromaculatus) consumed substantial amounts of D. lumholtzi. Although selectivity values for D. lumholtzi varied among these fish species, positive selection for D. lumholtzi increased similarly among larger size classes of each fish species, and corresponded with ontogenetic shifts in diet. Mean body length of D. lumholtzi consumed by 20–69 mm LT juvenile fishes ranged from 0·75 to 0·99 mm with a calculated total length range of 2·0–2·6 mm. Results from this study provide evidence that high abundances of D. lumholtzi in mid‐ to late‐summer provide an additional food source for several juvenile fish species during a time when abundances of large native cladoceran species (i.e. Daphnia) are low, and juvenile fishes are searching for larger prey associated with ontogenetic shifts from zooplankton to macroinvertebrates and fishes. Because zooplankton production is typically lower in rivers than in lakes, survivorship of juvenile fishes produced in floodplain lakes may be higher in riverine systems if they are not reliant on zooplankton as a primary food resource. Therefore, high abundances of D. lumholtzi may benefit juvenile fishes in managed floodplain lakes, such as Lake Chautauqua, by increasing growth and facilitating the transition from zooplanktivory to insectivory or piscivory.

Abundance and species richness as a function of food resources and vegetation structure: juvenile fish assemblages in rivers

Availability of food and habitat complexity are two factors generally invoked to explain the high density of fish in vegetated habitats. The role of food resources (zooplankton) and habitat complexity (expressed by a vegetation structural index) in determining juvenile fish abundance and fish species richness in three morphologically contrasted macrophyte types (Sagittaria, Ceratophyllum and Nuphar) was studied for a large, lowland river. Our results showed that fish abundance increased with food availability, and was maximal for intermediate values of vegetation complexity. Food resources and vegetation complexity did not, however, explain the higher juvenile fish abundance observed in Sagittaria beds. We suggested that plant growth form, acting on fish foraging success and risk of predation, might influence patterns of juvenile fish distribution. Species‐abundance relationships were similar among the three macrophyte types, but relationships between number of fish species (fish richness) and number of samples differed. Fish richness in terms of total number of fish species found at each sampling point showed the same pattern as for fish abundance: it increased with food availability and was highest at intermediate vegetation complexities. However, since both fish abundance and fish richness responded in the same manner to food availability and vegetation complexity, we were not able to distinguish statistically any effect for the specific fish richness formulated by the number of fish species per unit fish abundance. The current paradigm that structural complexity of vegetation provides a wider range of niches, increasing species diversity, was thus not verified. This finding indicates a simple species‐abundance relationship (the passive sampling hypothesis), and suggests that no special mechanism acts directly on fish species richness.

Cutaneous taste buds in gadoid fishes

Cutaneous taste buds occurred on the head and fins in five species of juvenile gadoid fishes from the west of Scotland, but there were significant differences in their density between regions on the fish and between species for individual regions. The highest taste bud densities were recorded on the edge of the anterior naris flap, the barbel, pelvic fin rays, snout tip and upper lip. Cod Gadus morhua and poor cod Trisopterus minutus had significantly higher taste bud densities on the first two pelvic fin rays than the other species. This appears to correspond with their more benthic lifestyle, in which the pelvic fins are frequently trailed over the sea bed when searching for prey.

Cutaneous taste buds in gadoid fishes

Cutaneous taste buds occurred on the head and fins in five species of juvenile gadoid fishes from the west of Scotland, but there were significant differences in their density between regions on the fish and between species for individual regions. The highest taste bud densities were recorded on the edge of the anterior naris flap, the barbel, pelvic fin rays, snout tip and upper lip. Cod Gadus morhua and poor cod Trisopterus minutus had significantly higher taste bud densities on the first two pelvic fin rays than the other species. This appears to correspond with their more benthic lifestyle, in which the pelvic fins are frequently trailed over the sea bed when searching for prey.

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.

Effects of brackish water on growth, feed conversion and energy absorption efficiency by juvenile euryhaline and freshwater stenohaline fishes

Among six species of juvenile fishes (&lt;6 months old), stenohaline species (channel catfishIctalurus punctatusand goldfishCarassius auratus) had their highest specific growth rate (G) and most efficient food conversion ratio (EC) and energy absorption efficiency (IE) in fresh water. Three of the euryhaline species (rainbow troutOncorhynchus mykiss, striped bassMorone saxatilisand Gulf sturgeonAcipenser oxyrinchus desotoi) had higherGand had more efficientECandIEin 3 and 9‰ salinities than in lower salinities (fresh water and 1‰). For brown troutSalmo trutta(age 3–4 months), 9‰ was above the optimum level forGandEC. However,IEfor brown trout was not significantly different at 3 and 9‰ salinities. Over the salinity range tested, channel catfish had the largest change inG,ECandIE, while changes for euryhaline species were relatively small. Although all species tested survived and grew in all treatments, salinities as low as 1‰ adversely affected the stenohaline species, and 9‰ adversely affected brown trout.

Assemblages of Southeast-South Brazilian Coastal Systems Based on the Distribution of Fishes

Multivariate principal components analysis and cluster analysis were performed on data representing presence or absence of 498 species of juvenile and adult fish species in twenty-four coastal marine systems (bays, coastal lagoons, estuaries and coastal zones) distributed from southeast to southern Brazil. Five groups of coastal systems were identified based on fish assemblage similarity: estuaries and bays of the southeast area; an estuary of the southern area; coastal lagoons; rocky coastal zones; and the continental platform. Species assemblages for each zone were identified and used as surrogate habitat indicators to compare and contrast the groups. Stepwise multiple regression of environmental and physical variables as predictors of the number of species indicated that only ‘area’ was included in the model as the most important variable explaining the variation of the number of species in these data sets. The total number of fish species increased as surface area increased.

Prevention of the Spread of Zebra Mussels during Fish Hatchery and Aquaculture Activities

Abstract Fish hatchery and aquaculture activities present numerous opportunities for accelerating the spread of zebra mussels Dreissena polymorpha to new locations. We tested aquaculture chemicals including NaCl, KCl, CaCl2, formalin, and the lampricide TFM (3-trifluoromethyl-4-nitrophenol) for efficacy against zebra mussel veligers and tolerance by several species of juvenile fish. Our short-term exposures simulated the high-stress environment of fish transport. High concentration of NaCl was the most effective treatment against veligers but also caused unacceptably high mortality in most fish species. A dilute solution of formalin (25 mg/L) in conjunction with KCl was effective against veligers and was safe for all fish taxa tested. However, concurrent exposures to 5,000 mg NaCl/L, which is commonly used to counteract fish shock during transport, decreased the toxicity of the formalin to veligers.