Fish Depth Research Articles

Fish and robots swimming together in a water tunnel: robot color and tail-beat frequency influence fish behavior.

The possibility of integrating bioinspired robots in groups of live social animals may constitute a valuable tool to study the basis of social behavior and uncover the fundamental determinants of animal functions and dysfunctions. In this study, we investigate the interactions between individual golden shiners (Notemigonus crysoleucas) and robotic fish swimming together in a water tunnel at constant flow velocity. The robotic fish is designed to mimic its live counterpart in the aspect ratio, body shape, dimension, and locomotory pattern. Fish positional preference with respect to the robot is experimentally analyzed as the robot's color pattern and tail-beat frequency are varied. Behavioral observations are corroborated by particle image velocimetry studies aimed at investigating the flow structure behind the robotic fish. Experimental results show that the time spent by golden shiners in the vicinity of the bioinspired robotic fish is the highest when the robot mimics their natural color pattern and beats its tail at the same frequency. In these conditions, fish tend to swim at the same depth of the robotic fish, where the wake from the robotic fish is stronger and hydrodynamic return is most likely to be effective.

Does the Fukushima NPP disaster affect the caesium activity of North Atlantic Ocean fish?

Abstract. Fillet samples of marine fish collected from the East/West Greenland currents (GC) and from the Baltic Sea (BS) have been investigated by gamma-ray spectrometry within the regular German monitoring programme. In samples of the second half of 2011, 134Cs traces have been detected that are suggested to originate from the Fukushima fallout that was deposited in March/April 2011 over the northern North Atlantic and accumulated by fish. The radionuclide 134Cs (half-life 2 yr) was indeed detected with quite small activities at about 0.0036 Bq kg−1 w.w. Existing box models describing the transport of Cs within seawater boxes of the northeast Atlantic allowed for estimation of 134Cs contributions from other sources, i.e. from the Chernobyl fallout and from discharges by the two major European nuclear reprocessing plants; both were negligible around Greenland, while for the Chernobyl fallout a small 134Cs background contribution to BS fish was estimated. Model results confirmed the level of 134C measured in BS fish and showed its maximum to have occurred in winter 2011/2012 followed by a continuous decrease. It was also determined that 134Cs activity, but not that of 134Cs, showed a significant negative correlation with sampling depth (150–400 m) of GC fish; this strengthens our Fukushima fallout assumption. As a result, the Fukushima fallout in these sea areas only marginally enhanced (GC: 4%; BS: 0.1%) pre-Fukushima levels of individual dose rates received by human fish consumers; the addition was around 0.001 μSv following the consumption of 10 kg of fish per year, which is not expected to cause concern according to present guidelines for radiation protection.

Trophic ecology of abundant reef fish in a remote oceanic island: coupling diet and feeding morphology at the Juan Fernandez Archipelago, Chile

The trophic structure of organisms is an important aspect of the ecosystem as it describes how energy is transferred between different trophic levels. Here, we studied the diet and foraging ecology of 144 individuals belonging to five abundant fish species of subtidal habitats at Isla Robinson Crusoe. Sampling was conducted during the austral spring and summer of 2007 and 2008, respectively. The shallow subtidal habitat is mainly characterized by the abundance of two types of habitat: foliose algae and encrusting invertebrates. Diet and trophic characteristic of fishes were obtained by volumetric contribution and frequency of occurrence of each prey item. Of the five species studied, one is herbivorous (juvenile Scorpis chilensis), four are omnivores (Nemadactylus gayi, Malapterus reticulatus, Pseudocaranx chilensis and Scorpis chilensis adult), and one carnivore (Hypoplectrodes semicinctum). The dietary diversity index was relatively low compared to other temperate reef systems, which could indicate a low availability of prey items for coastal fishes. The morphological parameters indicated that cranial structures and pairs of pectoral fins influence the foraging behaviour. Differences in fin aspect ratio among species provided insight about fish depth distribution and feeding behaviour. These results suggest important adaptive changes in the depth gradient of fishes in the subtidal environments of this island. According to our records, this is the first attempt to characterize the trophic ecology of the subtidal fish assemblages at Juan Fernandez Archipelago, revealing the need for testing hypotheses related to selective traits that may enhance species coexistence in oceanic islands.

FISH DEPTH DISTRIBUTIONS IN THE LOWER MISSISSIPPI RIVER

A substantial body of literature exists about depth distribution of fish in oceans, lakes and reservoirs, but less is known about fish depth distribution in large rivers. Most of the emphasis on fish distributions in rivers has focused on longitudinal and latitudinal spatial distributions. Knowledge on depth distribution is necessary to understand species and community habitat needs. Considering this void, our goal was to identify patterns in fish benthic distribution along depth gradients in the Lower Mississippi River. Fish were collected over 14 years in depths down to 27 m. Fish exhibited non-random depth distributions that varied seasonally and according to species. Species richness was highest in shallow water, with about 50% of the 62 species detected no longer collected in water deeper than 8 m and about 75% no longer collected in water deeper than 12 m. Although richness was highest in shallow water, most species were not restricted to shallow water. Rather, most species used a wide range of depths. A weak depth zonation occurred, not as strong as that reported for deep oceans and lakes. Larger fish tended to occur in deeper water during the high-water period of an annual cycle, but no correlation was evident during the low-water period. The advent of landscape ecology has guided river research to search for spatial patterns along the length of the river and associated floodplains. Our results suggest that fish assemblages in large rivers are also structured vertically. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Fishing down the deep: Accounting for within-species changes in depth of fishing

New estimates of the global mean depth of fishing, which consider both the between and within species changes over time, showed a stronger shift to deeper water than estimated previously based only on between-species changes. The new estimates show a linear increase in the mean depth of fishing of 62.5mdecade−1, corresponding to an increase of about 350m for the period since 1950. These values are about 5 times higher than those obtained by using between-species change in catch composition over time, suggesting that deep water species and habitats are under a more serious threat from fishing than hitherto assumed.

Assessment of Addictions among Fishermen in Southern-East Costal Area of Mumbai, India

Objective: Assessment of addictions and variables associated with them among fishermen in Southern-East Costal area of Mumbai. Material and Methodology: Present descriptive epidemiological study which had adopted exploratory survey design was carried out during Jan 2011 to June 2011. Total 500 fishermen were interviewed using preformed, pretested, semi-structured interview schedule. Results: The average age of fisherman was 34.9 + SD 14.9 years. Majority (81.6%) of fishermen had some kind of addictions. Alcohol and tobacco consumption was seen in 63.4% and 73.4% fishermen respectively. Job stress was seen in 67.8% of fishermen. Alcohol and Tobacco consumption were significantly associated with age, type of job, job stress, job satisfaction and depth of fishing. Misbelief of ‘tobacco and alcohol consumption increases work efficiency’ was prevalent among them. Conclusion and Recommendations: Rate of smoking and alcohol consumption was very high among fishermen. Fishermen may benefit from periodical health promotion and education in the area of smoking, alcohol consumption to raise their awareness about the dangers of smoking and alcohol consumption.

Giant grenadier Albatrossia pectoralis in the catches of the deepwater fishing traps in Russian far-eastern waters

The biological characteristics of the giant grenadier Albatrossia pectoralis and its spatial and vertical distribution of catches are considered based on the results of experimental fisheries of the deepwater fishes by the bottom traps in four regions of Russian far-eastern waters (Pacific waters of the south-eastern coast of Kamchatka, western part of the Bering Sea, ridge of Shirshov, waters around the Commander Islands). Changing of the catch sizes depending on the depth of fishing, soak time, and fishing area is analyzed; the questions concerned with eating away of fishes by amphipods (Amphipoda) are considered.

Sustainability of deep-sea fish species under the European Union Common Fisheries Policy

The historical expansion of fishing industries into the deep sea has been described at the global level, but corresponding patterns are less well known at other geographical scales. The International Council for the Exploration of the Sea (ICES) has stated that most deep-sea species exploited by European fishing industries are harvested outside safe biological limits. As a result, the European Union commenced regulating exploitation of deep-sea stocks with total allowable catches (TACs). These regulations have been operational since 2002, but no detailed overview of their effectiveness is hitherto available. The objectives of this paper are: 1) to analyse changes in mean depth of fishing of the EU fleet before (1950–1982) and after (1983–2006) the adoption of the Common Fisheries Policy (CFP), 2) to analyse the degree to which the European Council follows scientific advice on sustainable catches provided by ICES and 3) to investigate the degree to which the fishing industry complies with agreed catch limits. Our results indicate that the EU fleet has experienced a bathymetric expansion by an average of 78 m depth for the 1950–2006 period, or almost twice the value (42 m) previously reported for the global fleet. This pattern of expansion towards deep-sea fishing grounds has not changed under the CFP. Additionally, the paper demonstrates that the mean longevity of species caught by the EU fleet increased with depth, from about 13 years for shallow water species to about 25 years for intermediate species and about 60 years for deep-sea species. Thus, fishing deeper means fishing for increasingly long-lived and vulnerable species. This study also shows that approved TACs for deep-sea fish stocks did not follow scientific advice. Scientifically proposed TAC levels were not respected in about 60% of the cases investigated and these approved TACs were not complied. Member States exceeded agreed quotas in about 50% of the cases during the 2002–2011 period. Reported catches were on average 3.5 times greater than approved for deep-sea species, but in some cases catches even 10–28 times higher than agreed. The identified pattern that Member States fail to respect approved quotas indicate a lack of incentives to comply, likely as a consequence of limited enforcement and sanctioning mechanisms. Ensuring long-term sustainability of deep-sea stocks is urgently needed but requires dramatic change to the existing management system.

Hooking Survival of Fishes Captured by the United States Atlantic Pelagic Longline Fishery: Impact of the 2004 Circle Hook Rule

We examine the impact on pelagic fish hooking survival rates (defined as the proportion of fish alive upon gear retrieval) of the rapid switch from J-hooks to circle hooks that was required of the us pelagic longline fishery operating in the atlantic ocean and gulf of mexico after august 2004. Our focus was on 12 fish taxa that are commonly caught as bycatch or retained for the market, and for which individual disposition (live or dead) information was available from 1992 to 2010. To test the hypothesis of no change in survival before vs after the circle hook rule went into effect, we utilized a repeated measures logistic regression approach which accounted for variation in several operational, environmental, and biological covariates, including bait, fishery target, fishing zone, soak duration, water temperature, maximum fishing depth, and fish size (length). For white marlin and albacore, results were mixed, with both increases and decreases in hooking survival varying by fishing zone. For blue shark and lancetfish, no significant differences in hooking survival were detected between the pre- and post-circle hook rule time periods. However, for the remaining eight taxa (swordfish, yellowfin tuna, dolphinfish, bigeye tuna, escolar, silky shark, blue marlin, and sailfish), significant increases in survival were evident. Our results are generally consistent with previous experimental and fishery observer longline studies which suggested circle hook use has the potential to increase hooking survival. Results imply that the 2004 circle hook rule has provided increased opportunities for: (1) live release for several bycatch species; and (2) improved quality (and perhaps prices) of targeted and incidentally-caught taxa that are retained for the market.

Comparison of three standardised fish sampling methods in 14 alpine lakes in Austria

Abstract Standardised fishing methods using gillnets (EN 14575), electric fishing (EN 14011) and hydroacoustics (WI 00230244 CEN enquiry) to estimate species composition, abundance, biomass and size distribution were compared in 14 alpine lakes >50 ha. More fish species were detected using benthic gillnets (mean = 72.7%) than electric fishing (mean = 59.5%) and pelagic gillnets (mean = 29.6%). For all but two lakes, additional information from a local fisheries manager was required to obtain a complete list of species. Biomass data generated by standardised gillnetting and hydroacoustic surveys were not fully comparable, but a positive correlation was found. Gill netting and hydroacoustics both indicated a nearly fishless habitat below 75 m, which confirmed the maximum required fishing depth according to the European Standard EN 14757. Size distributions obtained from gillnet and hydroacoustic surveys differed statistically for large fish (>40 cm). Each standardised method reflected typical shortcomings. The European standard (EN 14757) should be amended for pelagic fish habitat in deep alpine lakes to include sampling effort corresponding to water volume, and additional gillnets with larger mesh sizes (e.g. 70 mm). Furthermore, the electric fishing standard (EN 14011) should be extended to incorporate requirements of lake fish sampling.

Cryptobenthic reef fishes: depth distribution and correlations with habitat complexity and sea urchins

In this study, cryptobenthic fish depth patterns and their correlations with habitat complexity and sea urchin densities were investigated. In general, total density, species richness and diversity were higher in the shallower zones (3 m), while evenness was higher at the 10 m depth zone. Among sites, species density was similar at the 10 m zone, but at the 3 m zone it varied greatly. Species-specific depth preferences were found. Correlation between species density and habitat complexity was usually positive. The influence of sea urchin densities on the cryptobenthic fish assemblage was site and species dependent.

Preliminary Findings on Distribution and Abundance of Flying fish in Relation to Oceanographic Conditions of Flores Sea Observed from Multi-spectrum Satellite Images

To describe the short term relationship between oceanographic conditions and flying fish catches and to visualize a spatial pattern of potential fishing grounds in the Flores sea, remotely sensed satellite images of sea surface temperature (SST), chlorophyll-a concentration, fishing depth and absolute geostrophic current together with catch data were used. Results indicated that the highest flying fish catch per unit efforts (CPUEs) occurred in areas of SST 27.5-29.5 °C, chlorophyll-a 0.25 0.70 mg. m -3 and current velocities 25.0 42.5 m. s -1 . The fishing depth locations have no significant correlation with the CPUEs. The three preferred oceanographic ranges provided a good indicator for spatially detecting the potential flying fish fishing grounds particularly in the peak season. The predicted potential fishing areas were located in the southwestern Takalar waters approximately 118°45‟E-119°40‟E and 5°30‟S-6°10‟S and were confirmed by the fishing data. It is likely that the potential fishing grounds correspond to the occurrence of the oceanographic structures such as upwelling and frontal zones which may be responsible for concentrating the fish schools. This short descriptive study suggests that these findings provide some preliminary results on the flying fish fishing grounds in the Flores Sea.

Seasonal and long‐term changes in fishing depth of Lake Constance whitefish

Abstract The ecosystem of Lake Constance in central Europe has undergone profound modifications over the last six decades. Seasonal and inter‐annual changes in the vertical distribution patterns of whitefish were examined and related to changes in biotic and abiotic gradients. Between 1958 and 2007, the average fishing depth in late summer and autumn was related to two factors influencing food supply of whitefish – lake productivity and standing stock biomass. In years with low food supply, whitefish were harvested from greater depths, where temperatures were up to 4 °C lower. The whitefish’s distribution towards colder water might be a bioenergetic optimisation behaviour whereby fish reduce metabolic losses at lower temperatures, or it may result from a reassessment of habitat preference under conditions of limited food supply, according to the ideal free distribution theory.

A review of the spatial extent of fishery effects and species vulnerability of the deep-sea demersal fish assemblage of the Porcupine Seabight, Northeast Atlantic Ocean (ICES Subarea VII)

Abstract Priede, I. G., Godbold, J. A., Niedzielski, T., Collins, M. A., Bailey, D. M., Gordon, J. D. M., and Zuur, A. F. 2011. A review of the spatial extent of fishery effects and species vulnerability of the deep-sea demersal fish assemblage of the Porcupine Seabight, Northeast Atlantic Ocean (ICES Subarea VII). – ICES Journal of Marine Science, 68: 281–289. We review information from scientific trawl surveys carried out between 1977 and 2002 in the Porcupine Seabight and Abyssal Plain area of the Northeast Atlantic (240–4865 m water depth). Since the late 1980s, commercial bottom-trawl fisheries targeting mainly roundnose grenadier (Coryphaenoides rupestris), black scabbardfish (Aphanopus carbo), and orange roughy (Hoplostethus atlanticus) have been operating at depths of 500–1500 m, intersecting the depth ranges of 77 demersal fish species that would therefore be vulnerable to fishery effects. Comparisons of trawls pre-1989 and post-1997 indicate a significant decrease in total abundance of demersal fish down to 2500 m. Detailed analyses of the 15 most-abundant species showed that nine species with depth ranges within the commercial fishing depth have decreased in abundance. Other species were either not affected (Bathypterois dubius) or only affected at the shallow end of their range (Coryphaenoides guentheri). Species with a minimum depth of occurrence >1500 m (Coryphaenoides armatus and Coryphaenoides leptolepis) increased in abundance over part of their depth range. Decreases in abundance are probably caused by commercial fishing activities, an effect that is transmitted downslope by removal of fish at the shallow end of their depth range, resulting in declines at the deeper end of the depth range. The estimated fishery area is ca. 52 000 km2, but the potential impact probably extends to ca. 142 000 km2 and to many non-target species.

Effect of line shooter and mainline tension on the sink rates of pelagic longlines and implications for seabird interactions

Abstract1. The likelihood that seabirds will be hooked and drowned in longline fisheries increases when baited hooks sink slowly. Fishermen target different fishing depths by setting the mainline through a line shooter, which controls the tension (or slackness) in the line. An experiment was conducted in Australia's pelagic longline fishery to test the hypothesis of no difference in sink rates of baited hooks attached to mainline set under varying degrees of tension.2. Mainline was set in three configurations typically used in the fishery: (a) surface set tight with no slackness astern; (b) surface set loose with 2 s of slack astern; and (c) deep set loose with 7 s of slack astern.3. Tension on the mainline had a powerful effect on sink rates. Baited hooks on branch lines attached to tight mainlines reached 2 m depth nearly twice as fast as those on the two loose mainline tensions, averaging 5.8 s (0.35 m s−1) compared with 9.9 s (0.20 m s−1) and 11.0 s (0.18 m s−1) for surface set loose and deep set loose tensions, respectively.4. The likely reason for the difference is propeller turbulence. Tight mainline entered the water aft of the area affected by turbulence whereas the two loose mainlines and the clip ends of branch lines were set directly into it about 1 m astern of the vessel. The turbulence presumably slowed the sink rates of baited hooks at the other end of the branch lines.5. The results suggest that mainline deployed with a line shooter (as in deep setting) into propeller turbulence at the vessel stern slows the sink rates of baited hooks, potentially increasing their availability to seabirds. Unless mainline can be set to avoid propeller turbulence the use of line shooters for deep setting should not be promoted as an effective deterrent to seabirds. Copyright © 2010 John Wiley & Sons, Ltd.

From Inflation to Flotation: Contribution of the Swimbladder to Whole-Body Density and Swimming Depth During Development of the Zebrafish (Danio rerio)

Teleost fishes have body tissues that are denser than water, causing them to sink. Many teleosts therefore possess a gas-filled swimbladder that provides lift, allowing fish to attain neutral buoyancy. The importance of the swimbladder as a buoyancy aid during changing body sizes over ontogeny and its role in determining the swimming depth of fish remain unclear. In this study, we have used the zebrafish (Danio rerio) to investigate changes in the size and shape of the swimbladder during development and examine whether these changes affect the hydrostatic contribution of the swimbladder during swimming. Our results showed that swim-up behavior is critical for larvae to first inflate their swimbladder, decrease body density, and attain neutral buoyancy. Following inflation, we found a strong linear correlation between fish volume and swimbladder volume over ontogeny. This trend was supported by measures of the density of zebrafish, which was conserved within a narrow range between 1.00 +/- 0.001 and 0.996 +/- 0.001 g/cm(3) despite an increase in the swimming depth of zebrafish, which occurred upon transition to a double-chambered organ. Finally, we demonstrated that the contribution of the swimbladder keeps the fish within 1.7% of neutral buoyancy throughout larval development.

Silent ships sometimes do encounter more fish. 1. Vessel comparisons during winter pollock surveys

Abstract De Robertis, A., Wilson, C. D., Williamson, N. J., Guttormsen, M. A., and Stienessen, S. 2010. Silent ships sometimes do encounter more fish. 1. Vessel comparisons during winter pollock surveys. – ICES Journal of Marine Science, 67: 985–995. Avoidance of approaching vessels by fish is a major source of uncertainty in surveys of fish stocks. In an effort to minimize vessel avoidance, international standards for underwater-noise emission by research vessels have been established. Despite widespread investment in noise-reduced vessels, the effectiveness of noise reduction on vessel avoidance remains poorly understood. Here, we report on vessel comparisons of pollock abundance recorded by the NOAA ships “Oscar Dyson” (OD), a noise-reduced vessel, and “Miller Freeman” (MF), a conventionally designed vessel. The comparisons were made during three acoustic surveys of prespawning aggregations of walleye pollock (Theragra chalcogramma) in Alaska. The experiments demonstrate that a noise-reduced vessel will detect significantly more fish backscatter than a conventional vessel in some situations. OD detected 31% more pollock backscatter than MF in the Shumagin Islands, where pollock were distributed between 100 and 200 m deep, and 13% more pollock backscatter in Shelikof Strait, where pollock were primarily distributed 200–300 m deep. However, there was no difference in the Bogoslof Island area where pollock were found at 400–700 m. In the Shumagin and Shelikof areas, the discrepancy between vessels tended to decrease with fish depth, consistent with a decreasing response to a stimulus propagating from the surface. Analysis of the depth distributions of pollock supports the conclusion that the discrepancies in backscatter stem from differential behavioural responses to the two vessels.

Low-frequency target strength and abundance of shoaling Atlantic herring (Clupea harengus) in the Gulf of Maine during the Ocean Acoustic Waveguide Remote Sensing 2006 Experiment

The low-frequency target strength of shoaling Atlantic herring (Clupea harengus) in the Gulf of Maine during Autumn 2006 spawning season is estimated from experimental data acquired simultaneously at multiple frequencies in the 300-1200 Hz range using (1) a low-frequency ocean acoustic waveguide remote sensing (OAWRS) system, (2) areal population density calibration with several conventional fish finding sonar (CFFS) systems, and (3) low-frequency transmission loss measurements. The OAWRS system's instantaneous imaging diameter of 100 km and regular updating enabled unaliased monitoring of fish populations over ecosystem scales including shoals of Atlantic herring containing hundreds of millions of individuals, as confirmed by concurrent trawl and CFFS sampling. High spatial-temporal coregistration was found between herring shoals imaged by OAWRS and concurrent CFFS line-transects, which also provided fish depth distributions. The mean scattering cross-section of an individual shoaling herring is found to consistently exhibit a strong, roughly 20 dB/octave roll-off with decreasing frequency in the range of the OAWRS survey over all days of the roughly 2-week experiment, consistent with the steep roll-offs expected for sub-resonance scattering from fish with air-filled swimbladders.

Target Strength for Fish Identification Using Echo Sounder

Identification of target strength (TS) of fish species in the South China Sea has been conducted using Furuno FQ-80(38/120 kHz echo sounder). This study introduces new experimental method which is combination of in situ and ex situexperiment by applying net cage at undersea. This research involved Selar boops (Oxeye scad) and Megalaspis cordyla(Torpedo scad) in separate net cage at the bottom of the vessel. TS, depth, and position (x-y-z) of fish have beenmonitored at every ping using echogram. TS of Selar boobs at low and high frequency are -44.49 dB for source level(SL) of 236dB and -43.96 dB for SL of 228 dB. For Megalaspis cordyla, TS are -45.34 dB (SL = 230 dB) and -43.06dB (SL = 225 dB) for low and high frequency respectively. The results show that Megalaspis cordyla produce higherTS whereas the position is deeper and smaller size than Selar boops at low and high frequency.

Population density imagery of migrating herring shoals by ocean acoustic waveguide remote sensing.

Ocean acoustic waveguide remote sensing (OAWRS) is a bistatic multibeam wide area sonar system that enables unaliased monitoring of fish populations over ecosystem scales. This allows us to quantify the formation processes of vast shoals of Atlantic herring (Clupea harengus) containing hundreds of millions of individuals, imaged during the Autumn 2006 spawning season. Areal population density estimation requires calibration of the low-frequency target strength of an individual shoaling herring. This is estimated from experimental data acquired simultaneously at multiple frequencies in the 300–1200-Hz range using (1) the OAWRS system, (2) areal population density calibration with several conventional fish finding sonar systems (CFFS), (3) fish length distributions obtained from trawl samples, and (4) local low-frequency transmission loss measurements. High spatial-temporal co-registration was found between shoals imaged by OAWRS and concurrent CFFS line transects, which also provided fish depth distributions. The mean scattering cross-section of an individual shoaling herring is found to exhibit a strong dependence on frequency in the OAWRS range, which is consistent with resonant scattering from an air-filled swimbladder. We show that a rapid transition from disordered to highly synchronized behavior occurs as the herring population density reaches a critical value, after which an organized group migration occurs.