Size Range Of Fish Research Articles

An assessment of the size structure, distribution and behaviour of fish populations within a temporarily closed estuary using dual frequency identification sonar (DIDSON)

The fish populations within the East Kleinemonde Estuary, South Africa, were studied using Dual frequency IDentification SONar (DIDSON) during March 2010 which allowed for direct comparisons of the abundance, distribution and behaviour of a wide size range of fishes along the length of the system. Small schooling fishes <100 mm in total length (L(T) ) were most abundant while larger size classes 100-300 and 300-500 mm were less abundant, but evenly distributed longitudinally within the estuary. Fishes <100 mm were most abundant within the mouth region which may reflect the feeding ecology of species that fall into these size classes and the effects of higher turbidities further up the estuary. Large fishes >500 mm were similarly most abundant near the mouth, and fishes of this size being mostly piscivorous, probably showed these distribution patterns due to the location of smaller prey fishes. Differential behaviour was observed among the longitudinal sections, with small fishes forming schools in areas of low turbidity and particularly in the presence of large predatory fishes. Results from this study present a snap-shot of the composition, distribution and behaviour of the ichthyofauna within a small temporarily closed estuary, and also show that abiotic factors and interactions of various size classes can influence their distribution. There is significant potential for DIDSON in future ecological research within these systems.

Testing Predictions of Stream Landscape Theory for Fish Assemblages in Highly Fragmented Watersheds

Predictions of stream landscape theory were tested with common agency fishery data in watersheds heavily fragmented by dams and barriers; large stream fragments support higher species diversity, more abundant populations, and a greater range of fish sizes. Study watersheds discharge to the Hudson River in New York USA, drain rocky and high relief landscapes, and have numerous mill dams and stream barriers. Stream fragments with fish collections ranged from 0.3 km to 119 km in contiguous length. Larger stream fragments had more diverse fish communities but not higher fish densities nor a wider range of fish sizes. However, almost all large stream fragments were supporting reproduction and rearing of the dominant stream species (brown trout Salmo trutta, brook trout Salvelinus fontinalis) while small fragments had no evidence of providing this fish community support. Therefore, consistent with the fundamental basis of stream landscape theory, large stream networks provide support for more species and more secure populations. The study supports the concept that diverse fish communities and secure populations benefit from access to a wide range of stream habitats.

Laboratory Evaluation of Two Bioenergetics Models for Brown Trout

AbstractLaboratory growth and food consumption data for two size‐classes of brown trout Salmo trutta subjected to three distinct feeding regimes at two temperatures were used to evaluate the ability of two bioenergetics models to predict fish growth. Accuracy of cumulative consumption predictions was also tested for one of the models. Consumption‐dependent prediction error has been commonly observed in bioenergetics models for other fish species; model errors for predicting relative growth rate of individual fish were regressed on observed mean daily consumption rate to assess whether the two bioenergetics models exhibited this type of error. Both models yielded unbiased estimates of brown trout growth that were within 1–12% of observed values across the range of fish sizes, water temperatures, and ration levels tested. For regressions of predicted versus observed final weight, the Bonferroni joint 95% confidence intervals for slope included 1 and confidence intervals for the y‐intercept included 0 for both models. No significant intermodel differences in percent error for predicting final weight of fish in feeding trials were observed. Predicted cumulative consumption values were within 8–15% of corresponding observed values. Neither model exhibited significant consumption‐dependent error for predicting brown trout growth, in contrast to results of several previous laboratory evaluations of bioenergetics models for other fish species. Absence of consumption‐dependent error in the two brown trout models may be a result of (1) incorporating feeding rate dependence of egestion and excretion into these models and (2) using egestion and excretion parameters that were not borrowed from other species. Results of this evaluation corroborate the utility of these bioenergetics models for predicting growth and consumption for brown trout under the range of fish sizes, water temperatures, and ration levels tested.

Size matters: comparing stable isotope ratios of tissue plugs and whole organisms

Stable isotope analysis provides an integrated measure of diet source and trophic position and is becoming an increasingly popular tool in studies of food web structure and function. However, stable isotope analysis can require sacrificing whole organisms, which is not always practical or ethical. As an alternative, biopsy punches cause minimal mortality in fish and provide enough sample for stable isotope analysis. Researchers commonly use smaller tissue samples for stable isotope analysis. Such analyses rely on the untested assumption that the stable isotope ratios from small tissue samples are representative of whole organism stable isotope ratios. Here we test this assumption by comparing stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) from tissue plugs and whole organisms over a range of fish sizes. We show that plugs from fish smaller than approximately 90 mm total length introduce a positive bias in δ15N. For larger fish, plugs provide a reliable and accurate means of measuring δ15N and δ13C, with the caveat that they introduce some variability in δ13C. Inclusion of overlying skin did not affect stable isotope measurements in our tissue samples.

Evaluating migratory fish behaviour and fishway performance: testing a combined assessment methodology

To provide passage for migratory native fish, a series of 14 vertical-slot and lock fishways are being constructed on the Murray River in south-eastern Australia. Three of these vertical-slot fishways, at Locks 7, 9 and 10, have a conservative slope (1V : 32H) and are designed with internal hydraulics suitable for the passage of a broad size range of fish (30–1000 mm long). An assessment of these fishways was performed using a combined trapping survey and passive integrated transponder (PIT) approach to determine fishway effectiveness at passing an entire fish community. Fish were trapped within the three fishways between 2004 and 2006, where a total of 13 626 individuals comprising 13 species were collected from 48 sample days (24 h each). Trapping data revealed that the three fishways successfully passed fish within the target size range, though significantly greater numbers of individuals smaller (10–29 mm long) than the target size range could not ascend. PIT tagging revealed important information on fishway ascent times, descent times, seasonality and diel behaviour of medium and large fish. Although each method alone had advantages and disadvantages, the dual assessment approach was useful as it permitted an assessment of fishway success and also provided insights into migratory fish behaviour.

Stock Structure and Dynamics of Longnose Gar and Shortnose Gar in the Wabash River, Indiana-Illinois

ABSTRACT Little information exists on the stock characteristics and dynamics of longnose gar (Lepisosteus osseus) and shortnose gar (Lepisosteus platostomus). We examined the size and age structure, mortality, growth, and condition of both species from the Wabash River, Indiana-Illinois, from June through August 2006. Longnose gar ranged from 492 to 1,224 mm in total length (TL) and from 250 to 5,600 g in wet weight (WW), while shortnose gar ranged from 498 to 776 mm in TL and from 350 to 1,900 g in WW Longnose gar and shortnose gar ranged in age from 2 to16 and 2 to12 years, respectively. Total annual mortality ranged from 13 to 17% for longnose gar and from 25 to 29% for shortnose gar. Annual growth in length was most rapid through age 6 for longnose gar (range, 18 to 100 mm/yr) and age 4 for shortnose gar (range, 9 to 48 mm/yr). Variation in relative condition of longnose gar and shortnose gar was heterscedastic over the size range of fish collected, but there was no significant relationship between relative condition and total length.

Blue sucker stock characteristics in the Wabash River, Indiana–Illinois, USA

Abstract Blue sucker, Cycleptus elongatus (Lesueur), populations have declined because of habitat degradation and overharvest, and little information exists on the population characteristics and stock dynamics of this species. We examined size and age structure, mortality, growth and condition of blue sucker in the Wabash River, Indiana–Illinois, USA. A total of 356 fish collected by electric fishing from June 2003 to April 2006 ranged from 238 to 775 mm total length and 85 to 5288 g wet weight. Age ranged from 3 to 16 years and annual mortality ranged from 22 to 25%. Annual growth was greatest among younger age classes (range 48–141 mm yr−1) and declined after age 6, likely at the onset of reproductive maturity. Variation in the relative condition factor (range 66–141) was heteroscedastic over the size range of fish sampled, perhaps attributable to seasonal differences in reproductive condition among mature fish.

The present status of the hook fishery and its impact on the fish stocks of Lake Victoria

Surveys on the hook fishery of Lake Victoria revealed that long lines are the most important gear used for catching Nile perch. Hand lines and hook and line are used to catch Nile tilapia and also Nile perch. Hooks are increasing because of their cheapness. They now total about 12 million lake-wide. Hooks are preferentially baited with live bait; they select the catch according to their sizes and bait type. Big range of fish sizes is caught. Hooks tend to reduce the size of the brood stock made up of big perch that carry millions of eggs. The use of live bait suppresses the recovery of resurging species with an adverse impact on the lake’s biodiversity. Use of the recommended hook sizes 4-9 should be enforced and overcapacity reduced for sustenance of the fish stocks. The farming of bait fish should be encouraged for standardisation of bait size to target the right size of the catch and spare the recovering species.

A factorial growth and feed utilization model for barramundi,Lates calcariferbased on Australian production conditions

To optimize feeds and feed management for barramundi (Lates calcarifer), an improved factorial model is required. A growth function describing weight gain by barramundi as a function of fish weight and water temperature was derived from farm and laboratory data. The function was of the form: A maintenance energy demand function was also derived on a similar form and two functions combined to form the basis of a factorial model for this species. An assessment of protein and energy utilization efficiency was undertaken to examine the effect of fish size on the estimation of these parameters. Fish size had a significant effect on energy utilization efficiency on a linear basis, but no such difference was observed if the data were considered using non-linear methods. Protein utilization efficiency was also observed to be clearly non-linear, and although protein deposition capacity differed with fish size, the efficiencies of protein utilization were not affected. Using this factorial model, optimal iterative feed specifications were defined for a range of fish sizes and formulation constraints. A feed demand model was also developed based on the demand for digestible energy.

Some Aspects of the Biology of Tilapia Zillii (Gervais) (Pisces: Cichlidae) in Opa Reservoir, Ile-Ife, Nigeria

Some aspects of the biology of Tilapia zillii were examined between October 1997 and February 2000. Fish specimens were collected using a graded set of gillnets and castnets. Out of 1486 fish specimens, 867 were males while 619 were females. Regardless of their sex a significantly high number of fish were caught inshore (69.57%) than in the offshore areas (30.43%). In addition 48.65% of all fish specimens were caught in the middle segment of the reservoir. A wide range of fish sizes were caught and the species was not spatially distributed (&#9672cal. 27.39

Do fish locks have potential in tropical rivers?

AbstractThis study evaluated attraction and passage of native fish through an automated fish lock on the tropical Fitzroy River in north‐eastern Australia. In 69 samples (24 h each) taken at the exit and entrance of the fish lock, 17 fish species and 13 402 individuals were collected, at a maximum rate of 3317 fish per day. During low river flows, the fish lock transferred a broad size range of fish (35–710 mm long), though migratory biomass was small. Removal of a vertical fish‐crowding device did not affect the passage rate. Netting studies and observations of fish migrating below the weir suggested that the entrance was poorly located during high flows and another fishway near the spillway would enhance fish passage. The fish lock was inoperative for 48% of the time, due to mechanical and software failure, and a narrow operational range unsuited to the variable hydrology. Nevertheless, these design issues are site specific and reflect that fish lock technology is in its infancy in Australia. The operational reliability of the fish lock is now greatly improved but further work is needed to optimize the automatic cycling. To accommodate the inherently variable hydrology of lowland tropical/sub‐tropical rivers into fishway design, we highlight important research needs for fishways and migratory fish communities. Fish locks are often considered a less favourable fish passage option but with the operational reliability issues partially resolved, they appear to have considerable potential for tropical river systems with low minimum flows and low biomass; with further research and design, they may have wider application. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Optimising Denil fishways for passage of small and large fishes

Abstract An 8‐m long experimental fishway was trialled at three different slopes [8.3% (1:12), 14.3% (1:7) and 20% (1:5)] to examine the potential of the single‐plane Denil fishway for the passage of small‐ and large‐bodied native fishes in Australia. Fish between 45 and 630 mm ascended the fishway. The lowest slope enabled the full size range of bony herring Nematalosa erebi (Günther), from 45 to 350 mm fork length, to ascend the fishway successfully as well as a higher numerical proportion; 88% at the 8.3% slope compared with 31% at the 20% slope (fish numbers per trial = 33–3936). These results dispel the notion that Denil fishways are inherently poor for small fishes. Manipulating the design parameters of slope, length, width and possibly depth‐over‐breadth ratio enables Denil fishways to pass a wide size range of fish, which may greatly extend their present application and enable them to make a greater contribution to the rehabilitation of diverse fish communities.

The roles of density, geometry, and short-range positional order in low-frequency acoustic scattering from fish schools

Fish can be efficient scatterers of low-frequency underwater sound. This results from the large response of their swim bladders to incoming acoustic waves at frequencies close to their natural resonance frequencies. For large and densely packed fish schools the scattering returns deviate significantly from what could be expected by adding the individual fish returns. These deviations are caused by multiple scattering between the individual fish in the school and concern the target strength as well as the spectral and directional characteristics of the scattering cross sections. Acoustically, a fish school can be viewed as a single object with acoustic bulk parameters determined from the properties of the individual fish and their positional arrangement in the school. This effective medium approach incorporates the acoustic coupling of all fish due to multiple scattering and works for a wide range of fish sizes, -numbers, and -densities. In this study, the effective medium approach as well as numerical computations from first physical principles are employed to investigate the coherent and diffusive low-frequency scattering cross sections of large and dense fish schools as a function of fish density, school geometry, and positional order among the individual fish. Inversions for these parameters are explored.

Factors influencing summer movement patterns of Bonneville cutthroat trout (Oncorhynchus clarkii utah)

We used multiple approaches to study summer movement patterns of Bonneville cutthroat trout (Oncorhynchus clarkii utah) in the Thomas Fork drainage of western Wyoming, USA. Our objectives were to (i) document summer movement patterns of cutthroat trout, especially as related to the concepts of local turnover and displacement distances, (ii) determine if fish size and condition were related to mobility, and (iii) compare summer movement patterns between years. Large fish (270–384 mm total length) monitored by radiotelemetry showed little movement during the summer as evidenced by a maximum displacement distance of &lt;300 m and a low turnover rate among locations (0.21). For a broad size range of fish marked with visual implant tags (173–390 mm total length) in three study reaches, displacement distances were again low but turnover rate was high (&gt;0.50 in most study reaches). This high turnover rate seemed to be driven mainly by movement among smaller fish as mobility declined with increasing fish size. Mobility also declined with decreasing body condition. Turnover rate in study reaches was higher during the summer of 1999 when stream flows were higher and water temperatures were cooler compared with the summer of 2000.

Effects of body size and temperature on metabolism of bream compared to sympatric roach

AbstractStandard (SMR) and routine (RMR) metabolic rates (mg O2 h−1) of bream, Abramis brama, were measured over a wide range of fish sizes and water temperatures (1-560 g wet mass, 5-23°C) by automated, computerised intermittent flow respirometry. These data were compared to similar data collected on roach, Rutilus rutilus, a sympatric species within the same subfamily Leuciscinae (Cyprinidae). For bream, both SMR and RMR were described by allometric mass exponents of 0.70 and exponential temperature dependencies over the entire size and temperature range. In bream, the temperature dependency of SMR and RMR was described by a Q10 of 2.8 and 2.2, respectively, while roach displayed Q10 values of 2.4 and 1.9, respectively. There were small but significant differences between bream and roach in the temperature dependency of SMR. Between 5 and 10°C, juvenile roach (Q10 = 5.8) and adult bream (Q10 = 4.9) displayed significantly higher sensitivity of mass-independent RMR to temperature changes than equal-sized juvenile bream and adult roach, respectively. This indicates different strategies during winter and the early spring period. When comparing these results with related literature about energy intake, it appears that roach and bream have evolved different thermal phenotypes, with bream showing a slightly more pronounced increase of metabolic energy loss and a less pronounced increase of energy intake (consumption, digestion) with temperature compared to sympatric roach.

Application of a bioenergetics model to roach

Summary A new set of bioenergetic parameters for adult roach (Rutilus rutilus) was fitted to the Wisconsin bioenergetics model (Fish Bioenergetics 3.0). These parameters describing rates of maximum food consumption, routine metabolism, egestion and excretion were derived from laboratory studies with adult roach over a wide range of fish sizes (1.2–300 g) and water temperatures (5–20°C). The new parameter set was compared with the only previously published set for adult roach, where parameters were taken from different life stages and compiled from different studies. In both a simulation and a field study, the new set resulted in a smaller increase of energy losses and a larger increase of energy intake with temperature compared with the previous set. The intermodel differences were most distinct at high (>20°C) and low (<10°C) temperatures, and can be mainly explained by differences in the temperature dependence of the respiration rate between the two sets. At moderate temperatures, the two parameter sets gave similar results.

A comparison of new in-pond grading technology to live-car grading for food-sized channel catfish (Ictalurus punctatus)

Grading trials were performed in experimental and commercial catfish ponds to compare an in-pond horizontal floating bar grader to current live-car grading. Three replicate trials were conducted in experimental ponds at three different temperature ranges (warm, >26°C; cool, 13–26°C; cold, <13°C) with catfish size groups stocked in ratios of either 75:25, 50:50, or 25:75 sub-marketable (<0.57kg) to marketable fish (≥0.57kg). Commercial pond trials were replicated three times at each temperature range with a fish size range typical of ponds ready to harvest. Stress experienced by fish during harvest and grading was measured by mean serum glucose and cortisol levels. Grading speed was greater (P < 0.05) with the UAPB grader (105–449kg/min) than the traditional live-car grader (0.5–0.6kg/min). The UAPB grader decreased (P < 0.05) the proportion of sub-marketable fish during all trials. In contrast, the live car did not reduce the proportion of sub-marketable fish with the experimental methods used in this study during commercial trials or in the 25:75 distributions during warm and cold temperature trials in experimental ponds. The UAPB grader returned an average two to four times (range of 2–52) more sub-marketable fish by weight to the pond than the traditional live car method. Glucose and cortisol levels in fish graded with the two technologies were not significantly different. The UAPB grader sorted fish more accurately, consistently, and quickly than the live car at all temperatures in both experimental and commercial trials.

The Effects of Age-0 Body Size on the Predictive Ability of a Largemouth Bass Bioenergetics Model

Abstract Bioenergetics models for largemouth bass Micropterus salmoides have provided scientists with a valuable tool for estimating growth and consumption based on temperature and the size of individuals. These models were developed for a wide range of fish sizes from various geographic origins and have been used to generate predictions for fish across the entire size and geographic ranges of largemouth bass. Although previous studies have shown general validity in model predictions, no validation has been achieved for smaller-bodied largemouth bass from differing geographic populations. To test the accuracy of a commonly used model at predicting the growth of small largemouth bass, we ran a series of six 14-d aquarium experiments that included controlled feeding rates over the range of average daily water temperature regimes in central Alabama. Age-0 largemouth bass from one population in Wisconsin (northern largemouth bass M. s. salmoides) and two populations in Alabama (Florida largemouth bass M. s. f...

Using a Modified Purse Seine to Collect and Monitor Estuarine Fishes

We developed a modified purse seine to sample shallow water estuarine habitats and evaluated the efficacy of using this gear as a tool for monitoring estuarine fish populations in Tampa Bay, Florida. The purse seine (183-m long, 5.2 m deep and 50-mm stretch mesh nylon throughout) was easily deployed and retrieved by a 7 m flat-bottomed, bow-driven boat with a hydraulic wench and aluminum pursing davit. Retention rates of pinfish (Lagodon rhomboides) marked and released into 35 net sets averaged 49% (range 9-100%). Retention rates were not significantly influenced by sets over vegetated and unvegetated bottom types, various water depths from 1-3.3m and sets with and without bycatch. We then used the modified purse seine to sample fishes at 550 randomly selected sites in Tampa Bay from January 1997 to December 1998. Sampled habitats ranged from 1.0 to 3.3 m deep and included seagrass beds and non-vegetated sand or mud bottoms. Benthic, demersal, and pelagic fishes were captured, indicating the purse seine effectively sampled the entire water column. A wide size range of fishes was collected including pre-recruitment sizes of several economically important species. The ability of purse seines to fish independent of adjacent shorelines allowed us to sample nearshore waters that included large expanses of sea grass meadow.

Dispersal of larvae and juveniles of Japanese anchovy Engraulis japonicus in the Kuroshio Extension and Kuroshio–Oyashio transition regions, western North Pacific Ocean

A sampling survey for Japanese anchovy Engraulis japonicus larvae and juveniles was carried out using two types of sampling gear for capturing a wide size range of fish in the Kuroshio Extension and Kuroshio–Oyashio transition regions in August 1996. Anchovy larvae were found widely far offshore. Total lengths (TLs) of the fish ranged mostly from 6 to 40 mm, which corresponded to 5–50 days after their hatching in July. The number of anchovy collected varied with sampling sites, but it was not clear what factors accounted for the variation. While the mean lengths of larvae taken in the Kuroshio Extension area tended to be smaller offshore, those in the transition area significantly increased in size as the distance offshore increased, perhaps because larger larvae migrated northward into the transition region. The mean growth rate of otolith-aged larvae was 0.63 mm per day, which was similar to those previously reported in the coastal waters. The daily mortality coefficient, which was estimated based on age–frequency distribution converted from length–frequency distribution, ranged from 0.362 to 0.136 per day. The mortality rates decreased with growth, being lowest for larger larvae offshore.