Fusiform Fish Research Articles

An experimental study on the size selectivity of fusiform fish by the netting characteristics

An experimental study on the size selectivity of fusiform fish by the netting characteristics

Examining Retention-at-Length of Pelagic Fishes Caught in the Fall Midwater Trawl Survey

The Fall Midwater Trawl Survey has provided data on aquatic organisms in the San Francisco Estuary for over five decades. In 2014–2015, a study was conducted to investigate and quantify the efficiency of this trawl for catching the endangered fish species Delta Smelt (Hypomesus transpacificus). In an analysis based on that study, we calculated retention probability—the probability that a Delta Smelt is retained in the cod end of the trawl—as a function of fish length and fit a selectivity curve reflecting the relationship between size and retention. Here we return to the same gear efficiency study and further utilize the data set by (1) fitting selectivity curves for three additional pelagic fish species: Threadfin Shad (Dorosoma petenense), American Shad (Alosa sapidissima), and Mississippi Silverside (Menidia beryllina), (2) refitting the selectivity curve for Delta Smelt to incorporate between-haul variability, and (3) calculating the lengths of 50% and 95% retention in order to characterize and compare the resulting selectivity curves. We also present retention data on age-0 Striped Bass (Morone saxatilis), all of which were retained in the cod end. We found that Threadfin Shad, American Shad, and Delta Smelt are 95% retained at 45, 49, and 61 mm fork length, respectively. Because data were limited for Mississippi Silverside, American Shad, and age-0 Striped Bass, we used body shape, in conjunction with retention data, to develop hypotheses about selectivity based on whether each species’ body shape resembles that of Threadfin Shad, which are more deep-bodied and laterally compressed, or Delta Smelt, which are more fusiform. We also found that retention-at-length was more variable for Delta Smelt than for Threadfin Shad, potentially because length is a good predictor of retention in deep-bodied, laterally compressed fish whereas maximum girth is a better predictor of retention in fusiform fish.

Using machine vision to estimate fish length from images using regional convolutional neural networks

Abstract An image can encode date, time, location and camera information as metadata and implicitly encodes species information and data on human activity, for example the size distribution of fish removals. Accurate length estimates can be made from images using a fiducial marker; however, their manual extraction is time‐consuming and estimates are inaccurate without control over the imaging system. This article presents a methodology which uses machine vision to estimate the total length (TL) of a fusiform fish (European sea bass). Three regional convolutional neural networks (R‐CNN) were trained from public images. Images of European sea bass were captured with a fiducial marker with three non‐specialist cameras. Images were undistorted using the intrinsic lens properties calculated for the camera in OpenCV; then TL was estimated using machine vision (MV) to detect both marker and subject. MV performance was evaluated for the three R‐CNNs under downsampling and rotation of the captured images. Each R‐CNN accurately predicted the location of fish in test images (mean intersection over union, 93%) and estimates of TL were accurate, with percent mean bias error (%MBE [95% CIs]) = 2.2% [2.0, 2.4]). Detections were robust to horizontal flipping and downsampling. TL estimates at absolute image rotations >20° became increasingly inaccurate but %MBE [95% CIs] was reduced to −0.1% [−0.2, 0.1] using machine learning to remove outliers and model bias. Machine vision can classify and derive measurements of species from images without specialist equipment. It is anticipated that ecological researchers and managers will make increasing use of MV where image data are collected (e.g. in remote electronic monitoring, virtual observations, wildlife surveys and morphometrics) and MV will be of particular utility where large volumes of image data are gathered.

Reef fish at a remote tropical island (Principe Island, Gulf of Guinea): disentangling taxonomic, functional and phylogenetic diversity patterns with depth

The ecology of reef fish varies with depth, although patterns in diversity remain largely undescribed, in particular the complementarity of their taxonomic, functional and phylogenetic facets. In the present study we investigated patterns of taxonomic, functional and phylogenetic diversity of fish on 21 reefs, at depths ranging from 3 to 31m, at Príncipe Island (Gulf of Guinea). Taxonomic and functional diversity decreased monotonically with depth; the pattern was less accentuated for phylogenetic diversity. Functional diversity was saturated at high levels of taxonomic diversity, reflecting redundancy in species traits, particularly at the shallower reefs. Functional diversity increased linearly with phylogenetic diversity; thus, increasing niche availability seems to translate into a larger diversity of phylogenies. Dissimilarities in the structure and composition of fish assemblages among reefs were correlated with differences in depth, including a progressive turnover in species. Depth affected the functional traits of nearshore reef fish. Trophic breadth decreased with depth; carnivores and planktivores increased with depth, whereas herbivores decreased with depth. Small-sized fusiform fish dominated on the shallowest reefs. In summary, the present study demonstrated decays in biodiversity, from different perspectives, of reef fish with depth, which are connected with shifts in fish traits.

A suitable ichthyometer for systemic application

An excessive and inappropriate handling of live fish is currently performed to obtain its size and weight. As an ameliorative attempt, a system named “IchthyoJHOL was devised for the measurement of live specimens of fusiform fish species. The system holds the fish ventrally between supports and is mounted upon a scale. An image is captured on camera and processed with a digital measurement system. The system generates biometric data such as length, height, and weight. This methodology creates a two-stage biometric process, the first being the capture of the images and the second their digital analysis, allowing for each stage to be carried out at distinct times and places. With this methodology, a reliability of over 96.8% is achieved, similar to that produced by the traditional system, but with a significant reduction in handling time and stress induced on the fish, allowing for large-scale biometric analysis. In addition, the library of fish images can be shared for posterior evaluation, redescription studies or a more extensive morphometric analysis.

Characterizing fish responses to a river restoration over 21 years based on species' traits.

Understanding restoration effectiveness is often impaired by a lack of high-quality, long-term monitoring data and, to date, few researchers have used species' trait information to gain insight into the processes that drive the reaction of fish communities to restoration. We examined fish-community responses with a highly resolved data set from 21 consecutive years of electrofishing (4 years prerestoration and 17 years postrestoration) at multiple restored and unrestored reaches from a river restoration project on the Lippe River, Germany. Fish abundance peaked in the third year after the restoration; abundance was 6 times higher than before the restoration. After 5-7 years, species richness and abundance stabilized at 2 and 3.5 times higher levels relative to the prerestoration level, respectively. However, interannual variability of species richness and abundance remained considerable, illustrating the challenge of reliably assessing restoration outcomes based on data from individual samplings, especially in the first years following restoration. Life-history and reproduction-related traits best explained differences in species' responses to restoration. Opportunistic short-lived species with early female maturity and multiple spawning runs per year exhibited the strongest increase in abundance, which reflected their ability to rapidly colonize new habitats. These often small-bodied and fusiform fishes typically live in dynamic and ephemeral instream and floodplain areas that river-habitat restorations often aim to create, and in this case their increases in abundance indicated successful restoration. Our results suggest that a greater consideration of species' traits may enhance the causal understanding of community processes and the coupling of restoration to functional ecology. Trait-based assessments of restoration outcomes would furthermore allow for easier transfer of knowledge across biogeographic borders than studies based on taxonomy.

Morphological change and phenotypic plasticity in response to water velocity in three species of Centrarchidae

Morphological responses to flowing water have been documented in many fishes, but rarely reported in species with gibbose body types, despite their use of riffles in rivers and streams. In this study, we compared morphological responses to water flow in three gibbose centrarchids: bluegill (Lepomis macrochirus Rafinesque, 1819), pumpkinseed (Lepomis gibbosus (L., 1758)), and rock bass (Ambloplites rupestris (Rafinesque, 1817)). Flow-through plexiglass units, set to either a sustained flow or static conditions, were used to rear juveniles from each species for an 80-day period. All three species developed more streamlined body forms, longer and thinner caudal peduncles, and longer pectoral fins when reared in sustained current. Pumpkinseed exhibited the highest level of phenotypic plasticity in response to water flow, followed closely by bluegill; rock bass was the least plastic species. Rock bass developed longer predorsal and prepectoral lengths, which differ from the morphological changes observed in bluegill and pumpkinseed. The findings not only suggest that some gibbose fishes are capable of exhibiting strong phenotypic responses to water flow, but that many morphological changes are species specific, even within the same taxonomic family. Lastly, all three species developed shorter dorsal fin base lengths when reared under flowing condition, which differs from some previously documented work on fusiform fishes. The results of this study provide a better understanding of how morphology in three closely related species varies in response to environmental conditions.

Habitat factors influencing fish assemblages at muskellunge nursery sites

Nearshore sites of the Great Lakes and their connecting channels provide critical nursery habitat for muskellunge (Esox masquinongy) and the fishes they prey upon. However, limited understanding of habitat–fish assemblage relations hinders informed management and restoration of these communities. To help fill this information gap, we (1) described fish assemblages at 25 sites in Buffalo Harbor (Lake Erie), the upper Niagara River, and the St. Lawrence River, (2) compared assemblages among sites and waters, and (3) determined if assemblage structure was related to habitat variation. The structure of fish assemblages at muskellunge nursery sites was influenced by suitability of habitats for particular reproductive strategies and providing refugia from predation. Sites that had flowing water, coarse substrates, high macrophyte column density, and little or no macroalgae supported greater fish densities and more species-rich assemblages that were dominated by small-bodied, fusiform cyprinids. These complex habitats provided refugia from predation and were suitable for open substratum spawners. Shallow sites with negligible stream flow, fine substrates, low macrophyte column density, and greater macroalgae coverage contained small-bodied, fusiform fishes; deeper sites with similar habitat were dominated by larger-bodied, laterally-compressed centrarchids and yellow perch (Perca flavescens), whose reproductive strategies and anti-predator adaptations allow them to persist in such habitats. Small-bodied, fusiform fishes such as banded killifish (Fundulus diaphanus), cyprinids, and darters are important prey for young-of-the-year muskellunge, whereas laterally-compressed centrarchids and yellow perch are typically avoided. Managing for habitats that support abundant fusiform fishes should provide better nursery conditions and promote stronger year-class formation for muskellunge.

Three different patterns of how low-intensity waves can affect the energy budget of littoral fish: a mesocosm study

In a mesocosm study, somatic and otolith growth of six types of juvenile cyprinids differing in body size and body shape were studied in a low-intensity wave treatment and a no-wave control. Depending on fish type, somatic growth was either reduced by up to 60% or increased by up to 50% following exposure to the wave treatment. Somatic growth and otolith daily increment width (ODIW), the latter being used as a proxy for the fish energy turnover, were compared to reveal the effects of waves on the energy budget of the fish. Three different reaction types to waves, which correlated to the body morphology of the six fish groups, could be distinguished. Small and fusiform fish benefitted from low-intensity waves and showed higher somatic growth rates and greater ODIW in the wave treatment. In small, deep-bodied fish, growth and ODIW were reduced by waves. Finally, in larger fish with either a fusiform or deep-bodied shape, ODIW was decoupled from somatic growth, with larger ODIW in waves, but reduced somatic growth. These results show that low-intensity hydrodynamic stress is a much more important and complex habitat factor than previously assumed. It is concluded that hydrodynamic stress by waves should be accounted for in bioenergetic models and studies on habitat choice in littoral fish species.

Are ontogenetic shifts in diet linked to shifts in feeding mechanics?Scaling of the feeding apparatus in the banded watersnakeNerodia fasciata

The effects of size on animal behaviour, ecology, and physiology are widespread. Theoretical models have been developed to predict how animal form, function, and performance should change with increasing size. Yet, numerous animals undergo dramatic shifts in ecology (e.g. habitat use, diet) that may directly influence the functioning and presumably the scaling of the musculoskeletal system. For example, previous studies have shown that banded watersnakes (Nerodia fasciata) switch from fish prey as juveniles to frog prey as adults, and that fish and frogs represent functionally distinct prey types to watersnakes. We therefore tested whether this ontogenetic shift in diet was coupled to changes in the scaling patterns of the cranial musculoskeletal system in an ontogenetic size series (70-600 mm snout-vent length) of banded watersnakes. We found that all cranial bones and gape size exhibited significant negative allometry, whereas the muscle physiological cross-sectional area (pCSAs) scaled either isometrically or with positive allometry against snout-vent length. By contrast, we found that gape size, most cranial bones, and muscle pCSAs exhibited highly significant positive allometry against head length. Furthermore, the mechanical advantage of the jaw-closing lever system remained constant over ontogeny. Overall, these cranial allometries should enable watersnakes to meet the functional requirements of switching from fusiform fish to bulky frog prey. However, recent studies have reported highly similar allometries in a wide diversity of vertebrate taxa, suggesting that positive allometry within the cranial musculoskeletal system may actually be a general characteristic of vertebrates.

Form and performance: body shape and prey-capture success in four drift-feeding minnows

Identifying links between morphology and performance for ecologically relevant tasks will help elucidate the relationships between organismal design and fitness. We conducted a laboratory study to quantify the relationship between variation in body shape and prey-capture success in four drift-feeding minnow species. We offered drifting prey to individual fish in a test flume, counted successful strikes to measure prey-capture success and recorded the position (X, Y coordinates) of ten landmarks on each fish's outline to delineate the specimen's form. We then quantified shape variation among species and related it to capture performance through thin-plate spline analysis. Body shape varied significantly among species and with specimen size and was the major determinant of capture success, explaining 45-47% of its variability. Prey-capture success at differing velocities differed among species, but once the effects of shape and size were accounted for, those differences were no longer significant. Allometric shape changes appeared responsible for most of the ontogenetic variation in capture performance, although other size-related, non-shape factors also seemed relevant. Fishes with deeper, shorter bodies, more caudally placed median fins and larger, more upward-pointing mouths exhibited greater capture success than more fusiform fish, suggesting that streamlining, which is energetically advantageous for sustained swimming, entails a cost in terms of prey-capture ability. Our findings demonstrate a strong connection between organismal shape and performance and provide empirical evidence of the cost of morphological specialization for fishes in the drift-feeding functional guild.

Comparison of Two External Transmitter Types on Two Sizes of Bluegills and Yellow Perch

AbstractWe compared two external transmitter styles on two size‐classes of bluegills Lepomis macrochirus (laterally compressed) and yellow perch Perca flavescens (fusiform) to determine the effects of (1) even distribution of transmitter weight and (2) transmitter weights above and below the recommended 2% of fish body weight. Fish were collected, acclimated for 3 weeks before transmitter attachment, measured for length and weight, Floy tagged, and randomly assigned to treatments (single‐sided transmitter, saddle transmitter, and control). Weight and length of individual fish were recorded every 5 d through day 20 and every 10 d through day 40. On day 40, we classified tag migration, wound redness, and organosomatic indices. Saddle transmitters required the longest handling time of all treatments and did not outperform single‐sided transmitters. On day 40, only small yellow perch had gained more weight with saddle transmitters than with single‐sided transmitters. Transmitters that exceeded 2% of fish weight slowed bluegill growth, whereas transmitters that were less than 2% of fish weight negatively affected yellow perch growth. Our results suggest that even the distribution of external transmitter weight may be less important than the method of attachment and transmitter weight. Development of improved attachment methods for saddle transmitters may prove beneficial for use in long‐term studies of small, fusiform fish.

A new genus of Triassic actinopterygian with an evaluation of deepened flank scales in fusiform fossil fishes

ABSTRACT Revision of the genus Peltoperleidus leads to recognition of a single persisting deepened scale row as the main diagnostic feature for the newly established genus Allisolepis gen. nov. The counts of deepened scale rows are taken to be very consistent in all species assigned to Peltoperleidus and Allisolepis gen. nov., since they can be perfectly matched with skull bone patterns and counts of lepidotrichia. An initial evaluation shows that presence and array of variably deepened flank scales in fusiform fossil fishes have previously been underestimated in terms of their occurrence and as a putatively phylogenetic signal: the counts of deepened flank scales show some negative correlation with body size in fusiform fishes up to a certain standard length only, and occur predominantly in smallest fishes in the Middle Triassic. No significant correlation exists between scale row counts and standard length with respect to taxonomy; although interrelationships of these actinopterygians are still poorly understood, it appears likely that similar patterns of deepened scale rows may have developed independently during the Early-Middle Triassic.

A new Late Cretaceous (Turonian) basal euteleostean fish from Lac des Bois of the Northwest Territories of Canada

A new genus and species of Late Cretaceous euteleost, Avitosmerus canadensis, is described from an assemblage of fossil fishes found in a Late Cretaceous (Turonian) unnamed member (unit E) of the Great Bear Basin from Lac des Bois, Northwest Territories, Canada. It is a small fusiform fish characterized by a long slender supraorbital, the presence of a small suprapreopercle, branches of the preopercular sensory canal that reach the edge of the preopercle, and an anterior supraneural that is twice as large as those posterior to it. Additionally, elements of its caudal fin show a high degree of fusion. Avitosmerus is one of ten described Cretaceous basal euteleosts that are found worldwide (Avitosmerus, Barcarenichthys, Erichalcis, Gaudryella, Gharbouria, Humbertia, Kermichthys, Manchurichthys, Paravinciguerria, and Stompooria). Avitosmerus and Erichalcis are the only two basal euteleosts that have been described from the Cretaceous of North America. Placement of Avitosmerus into the Euteleostei is based on the presence of a free stegural, and the large first supraneural. Both of these characters are somewhat controversial and are in need of reexamination. Avitosmerus shares a number of characters with the other Cretaceous basal euteleosts, as well as Recent basal euteleosts, including a separate rostrodermethmoid and mesethmoid (Gaudryella, Erichalcis, Gharbouria, the Osmeridae, and the Coregonidae), lobate condyles of the hyomandibula (Avitosmerus, Gaudryella, and Gharbouria), leaf-shaped neural spine on the first preural centrum (Kermichthys), and the fusion of the parhypural, first, and second hypurals (Gaudryella).

Modeling Seasonal Trophic Interactions of Adfluvial Bull Trout in Lake Billy Chinook, Oregon

We examined the trophic interactions of bull trout Salvelinus confluentus in Lake Billy Chinook, Oregon, using a bioenergetics model combined with data on annual growth, seasonal diet, distribution, and thermal experience to determine the seasonal and size-specific prey requirements of bull trout and the influence of bull trout predation on some of their major prey species in the reservoir. Per capita estimates of consumption were expanded to population-level estimates based on estimates of size structure and the abundance of the bull trout population. Bull trout became progressively more piscivorous with increasing size, and fish were the primary prey of predators of 450 mm fork length (FL) or more. Kokanee (lacustrine sockeye salmon Oncorhynchus nerka) and other salmonids (predominantly bull trout and rainbow trout O. mykiss) represented the largest fraction of fish prey in the diet, although cyprinids, cottids, and catostomids were also consumed. Predation on kokanee occurred primarily in autumn and secondarily in winter−spring. Predation by bull trout of less than 450 mm FL was greatest on smaller bull trout and rainbow trout in the reservoir during June−September, whereas predation by bull trout of 450 mm or more on salmonids other than kokanee was most prevalent during winter−spring. Bull trout of all sizes were capable of eating fusiform fish up to 50% of their own length. Given the size structure and estimated abundance of bull trout of 200 mm FL or more in Lake Billy Chinook during 1993 (3,600) and 1994 (8,400), model simulations indicated that annual predation removed large fractions of the bull trout (19–44% of age-0 fish and 7–16% of age-1 fish) and kokanee (5–11% of age-0 fish, 1–2% of age-1 fish, and 9–59% of fish of ages 2–3) populations. Thus, cannibalism and prey supply are potentially important factors limiting the abundance and production of bull trout in Lake Billy Chinook.

Is the High Cost of Body/Caudal Fin Undulatory Swimming Due to Increased Friction Drag or Inertial Recoil?

ABSTRACT Deep-bodied fish, such as the bluegill sunfish (Lepomis macrochirus), are considered to have relatively larger wetted surface areas for their size than fusiform fish. On the basis of the boundary layer thinning hypothesis attributing high power requirements of undulatory swimming to enhanced friction drag, power (=drag) coefficients should be higher for such fish. Areas are typically normalized with total length, L, as L2 for comparison among species. Bluegill had a wetted surface area of 0.65 L2, compared with areas of about 0.41 L2 for trout of similar mass. However, absolute areas and volume2/3 of bluegill and trout were similar. Power requirements and power coefficients calculated from kinematics during steady swimming were lower for bluegill sunfish than for cruisers, such as trout, and power coefficients were also lower than those of accelerators, such as tiger musky. Large body depth also damps inertial recoil arising from the side force generated largely by the tail. Inertial energy losses appear to be more important contributors than friction to mechanical power requirements.

Importance of the swimbladder in acoustic scattering by fish: A comparison of gadoid and mackerel target strengths

Previous determinations of the swimbladder contribution to the fish backscattering cross section have been hindered by ignorance of the acoustic boundary conditions at the swimbladder wall. The present study circumvents this problem by direct comparison of target strengths of three gadoid species and mackerel — anatomically comparable fusiform fish which respectively possess and lack a swimbladder. The relative swimbladder contribution to both maximum and averaged dorsal aspect backscattering cross sections is shown to be approximately 90% to 95%, which is higher than most other estimates. The new results were established for fish of 29- to 42-cm length and acoustic frequencies of 38 and 120 kHz.

Acute Effects of Underwater Construction Blasting on Fishes in Long Point Bay, Lake Erie

We detonated 201 blasts 22.7–272.4 kg per charge with a high explosive (Hydromex) in 4–8 m of water at Nanticoke, Lake Erie. Shortly after each blast turbidity and CO2 concentrations increased markedly, returning to ambient levels within 3 h of the blast. Postblast pressure and charge weight were directly related (r = 0.70, P < 0.05). Fatality radii ranged from 20 to 50 m for 22.7 kg per charge to 45–110 m for 272.4 kg per charge. Common blast-induced injuries were swimbladder ruptures and hemorrhaging in the coelomic and pericardial cavities. Laterally compressed species were more susceptible to blast pressure gradients than were the fusiform fishes. Temporally, surface mortalities were high only in the spring and late summer. Spatially, 47% of the total blast mortality was not visible from the water surface. Key words: blasting impact, hydraulic pressure gradients, fish mortality, species specific susceptibility

THE RELATION OF BODY WEIGHT TO BODY SURFACE AREA IN MARINE FISHES

The value of K in the formula S = K w⅔ has been determined for 39 species of marine teleosts representing 25 families. The values of K are in general higher for depressed and compressed species than for more streamlined fusiform fishes.

THE TRANSFORMATION OF ORGANIC DESIGNS: A REVIEW OF THE ORIGIN AND DEPLOYMENT OF THE EARLIER VERTEBRATES

THE TRANSFORMATION OF ORGANIC DESIGNS: A REVIEW OF THE ORIGIN AND DEPLOYMENT OF THE EARLIER VERTEBRATES