The use of anglers' catches to monitor fish populations in large water bodies, with particular reference to the River Derwent, Derbyshire, England

Abstract. Nearly 2000 marked coarse fish of four species were introduced into a stretch in the middle reaches of the River Derwent. Derbyshire, England in an attempt to estimate the fish population size from catch returns. It was estimated that 800 dace, 1975 roach, 1481 chub and 366 bream were present in the reach and the density of the fish population (0·35 fish m^?2) was low. The validity of employing anglers as samplers in a mark-recapture exercise to estimate fish population size in large fisheries is discussed. Angler catch data were collected from angling clubs holding competitions on the Hoveringham Fishery on the lower reaches of the River Derwent over the period 1973/1974 to 1983/1984 to assess the impact of achange in management strategy on the fishery in 1979. Catch rates improved gradually until 1979/1980 when a dramatic increase occurred. This elevated catch rate, in excess of 400 g man-h^?1, was maintained and, in recent years, further enhanced (>500 g man-h^?1). The improvement was the result of a strong year-class of chub entering the catchable cohort and dominating anglers' catches and not the change in management policy.     

A 'Before and After' Study of the Effects of Land Drainage Works on Fish Stocks in the Upper Reaches of a Lowland River

Fish stocks at a site in the upstream reaches of the River Soar, a lowland river in Leicestershire, showed a marked alteration following river channel works associated with a land drainage improvement scheme. The density and standing crop of all ‘large-sized’ fish species present showed reductions of 15–100% between a 6-month pre-drainage period and a 3-month post-drainage period. The density and standing crop of the total population were reduced from means of 0.160 fish m^?2 and 39.0 g m^?2 during the pre-drainage period to means of 0.048 fish m^?2 and 9.6 g m^?2 during the post-drainage period, reductions of 70% and 76%, respectively. It is suggested that modifications to physical features of fish habitat, particularly the elimination of in stream cover, were largely responsible for the decreased fish abundance.     

Rice with fish culture in the semi-deep waters of the Mekong Delta, Vietnam: interaction of rice culture and fish husbandry management on fish production

Fish husbandry and rice culture management factors influencing the yield of introduced fish in ricefields of the Vietnamese Mekong Delta were studied by multiple regression analysis. A significant (P < 0.001) regression model was computed in which feed input and duration of culture period positively and ricefield area, rice seeding rate and the year of the survey negatively affected the yield of introduced, as well as indigenous, fish. The negative impact of larger ricefields is probably the result of the escape of fish. This is also probably the reason for the year of survey since the average yield of introduced fish was 92.5 kg ha^?1 in 1995 (because of an extreme flood) as compared to 164.8 kg ha^?1 in 1994. A high seeding rate of rice results in a dense stand which suppresses the growth of fish. Opportunities for improvement of fish production are proper ricefield construction, reduced seeding rates, stocking fingerlings early in the dry season and more intensive feeding.     

Evaluations of rum distillation wastes,pharmaceutical wastes and chicken feed for rearing Tilapia aurea in Puerto Rico

Rum distillation wastes (solubles and yeast), pharmaceutical wastes (spent beer and spent beer plus solids), and a locally manufactured chicken feed were evaluated for their potential use in the culture of Tilapia aurea in Puerto Rico. The experimental products were compared to three types of controls: a commercial fish feed, an inorganic fertilizer, and an unmanaged system. The yield trials were conducted for 120 days in 9.3 m plastic pools. Three replications were made of each treatment. Survival of fish in the various treatments ranged from 80 to 96.7%. The highest mean standing crop at harvest (690 kg ha^?1 equivalent) resulted from the fish receiving the commercial fish feed. This was followed by the fish from the spent beer treatment (643 kg ha^?1 equivalent), inorganic fertilizer (559 kg ha^?1 equivalent), distiller's yeast (454 kg ha^?1 equivalent), spent beer plus solids (429 kg ha^?1 equivalent), chicken feed (413 kg ha^?1 equivalent), distiller's solubles (347 kg ha^?1 equivalent), and the unmanaged system (145 kg ha^?1 equivalent). The average feed conversion values for the fish fed the commercial fish feed and chicken feed were 1.53 and 2.06, respectively. Dissolved oxygen levels in pools treated with rum distiller's yeast declined from approximately 8.0 to 0.4 p.p.m. following initial application of the product. Dissolved oxygen depletions occurred after each subsequent application. All other systems had waters with dissolved oxygen concentrations generally suitable for fishculture.     

Evaluation of freshwater prawn‐small fish culture concurrently with rice in Bangladesh

An integrated aquaculture of freshwater prawn (Macrobrachium rosenbergii) and self‐recruiting small fish mola (Amblypharyngodon mola) was conducted in farmers' rice fields at Mymensingh, Bangladesh. There were four treatments with three replications. Four stocking densities, 10 000, 15 000, 20 000 and 25 000 ha^?1, of freshwater prawn were applied. The stocking density of mola was the same (20 000 ha^?1) in all treatments. During land preparation, triple super phosphate (TSP) and murate of potash (MP) were applied at the rate of 150 and 75 kg ha^?1 respectively. Urea was applied at the rate of 200 kg ha^?1 in equally distributed three installments after 16, 45 and 65 days of rice plantation. Prawns were fed with commercial pelleted feed at 3–8% body weight. All water quality parameters were found to be within the suitable range for freshwater prawn culture. There was a homogenous abundance of plankton communities in all treatments. The results of a 4‐month culture period showed that the average production of prawn ranged from 222 to 388 kg ha^?1, mola 51 to 68 kg ha^?1 and rice 2 880 to 3 710 kg ha^?1. Significantly higher production of both prawn and mola was recorded in the plots where the freshwater prawn stocking density was 15 000 ha^?1. This treatment resulted in a net profit of USD 1100 ha^?1.     

Individual movements,home ranges and habitat use by native rheophilic cyprinids and non‐native catfish in a large regulated river

The mobility patterns of two native species, barbel, Barbus barbus (L.) and chub, Squalius cephalus (L.), and of one non‐native fish species, the catfish Silurus glanis (L.), were assessed on a 35.5‐km reach of the Upper Rhône River, a strong flowing river with notable thermal regime alterations. An active acoustic tracking technique adapted to large rivers allowed (1) the identification of longitudinal home ranges, movements and preferred habitat at large scale, and (2) the analysis of the influence of discharge and water temperature on the movement patterns of the fish. The active fish‐tracking system recorded 1,572 fish localisations over 7 months on a weekly basis for 80% of the tagged fish (37 barbel, 23 chub and 13 catfish). Compared with the catfish, barbel and chub showed wider longitudinal home ranges, more movements >1 km and higher interindividual variability. The catfish preferred artificially heated habitats with less morphological diversity. The three species were more often localised in river sections with high density of woody debris. The results suggest that habitat degradation is more damaging for cyprinids in large modified rivers, while the catfish seemed less, impacted.     

Habitat use and population structure of four native minnows (family Cyprinidae) in the upper Missouri and lower Yellowstone rivers, North Dakota (USA)

Abstract – In 1997 and 1998, sampling was conducted on the Missouri and Yellowstone rivers, North Dakota, to obtain information on the distribution, abundance, and habitat use of the flathead chub (Platygobio gracilis Richardson), sicklefin chub (Macrhybopsis meeki Jordan & Evermann), sturgeon chub (Macrhybopsis gelida Girard), and western silvery minnow (Hybognathus argyritis Girard), four declining fish species (family Cyprinidae) native to the Missouri River basin, USA. The study area consisted of four distinct river segments near the confluence of the Missouri and Yellowstone rivers – three moderately altered segments that were influenced by a main‐stem dam and one quasi‐natural segment. One moderately altered segment was located at the confluence of the two rivers (mixing‐zone segment (MZS)). The other two moderately altered segments were in the Missouri River adjacent to the MZS and extended up‐river (above‐confluence segment (ACS)) and down‐river (below‐confluence segment (BCS)) from this segment. The quasi‐natural segment (Yellowstone River segment (YRS)) extended up‐river from the MZS in the Yellowstone River. Catch rates with the trawl for sicklefin chub and sturgeon chub and catch rates with the bag seine for flathead chub and western silvery minnow were highest in the BCS and YRS. Most sicklefin and sturgeon chubs were captured in the deep, high‐velocity main channel habitat with the trawl (sicklefin chub, 97%; sturgeon chub, 85%), whereas most flathead chub and western silvery minnow were captured in the shallow, low‐velocity channel border habitat with the bag seine (flathead chub, 99%; western silvery minnow, 98%). Best‐fit regression models correctly predicted the presence or absence of sicklefin chub, flathead chub, and western silvery minnow more than 80% of the time. Sturgeon chub presence and absence were predicted correctly 55% of the time. Best‐fit regression models fit to fish number data for flathead chub, sicklefin chub, and sturgeon chub and fish catch‐per‐unit‐effort (CPUE) data for flathead chub also provided good fits, with R² values ranging from 0.32 to 0.55 (P < 0.0001). The higher density and catch of the four native minnows in the YRS and BCS suggest that these two segments are better habitat than the ACS and MZS.     

The potential of mixed culture of genetically improved farmed tilapia (Oreochromis niloticus) and freshwater giant prawn (Macrobrachium rosenbergii) in periphyton-based systems

The production performance of genetically improved farmed tilapia (GIFT, Oreochromis niloticus) and freshwater prawn (Macrobrachium rosenbergii) in periphyton‐based systems were studied in farmers' ponds at Mymensingh, Bangladesh. Fifteen ponds (200–300 m² area and 1.0–1.5 m in depth) were used to compare five stocking ratios in triplicate: 100% GIFT, 75% GIFT plus 25% prawn, 50% GIFT plus 50% prawn, 25% GIFT plus 75% prawn and 100% prawn. Ponds were stocked at a total density of 20 000 GIFT and/or prawn ha^?1. Bamboo poles (mean diameter 6.2 cm and 5.5 pole m^?2) were posted in pond bottoms vertically as periphyton substrate. Periphyton biomass in terms of dry matter (DM), ash‐free DM and chlorophyll a were significantly higher in ponds stocked with prawn alone than in ponds with different combinations of GIFT and prawn. Survival of GIFT was significantly lower in ponds stocked with 100% GIFT (monoculture) whereas, that of prawn was significantly higher in its monoculture ponds indicating detrimental effects of GIFT on prawn's survival. Individual weight gains for both species were significantly higher in polyculture than in monoculture. The highest total fish and prawn yield (1623 kg GIFT and 30 kg prawn ha^?1) over 125–140 days culture period was recorded in ponds with 75% GIFT and 25% prawn followed by 100% GIFT alone (1549 kg ha^?1), 50% GIFT plus 50% prawn (1114 kg GIFT and 68 kg prawn ha^?1), 25% GIFT plus 75% prawn (574 kg GIFT and 129 kg prawn ha^?1) and 100% prawn alone (157 kg ha^?1). This combination also gave the highest economic return. Therefore, a stocking ratio of 75% GIFT plus 25% prawn at a total density of 20 000 ha^?1 appeared to be the best stocking ratio in terms of fish production as well as economics for a periphyton‐based polyculture system.     

Influence of poultry manure on growth of Oreochromis shiranus chilwae

Poultry manure added to concrete ponds lined with 5 cm of soil increased fish growth only when applied up to a rate equivalent to 470 kg ha^?1 week^?1. When manure was supplied at 940 kg ha^?1 week^?1 fish growth was significantly (P < 0.05) reduced. Parameters which may explain the lower fish growth were electrical conductivity, pH, alkalinity, phosphorus and chlorophyll a production. Dissolved oxygen values fluctuated from 3 to 25 mg l^?1 at 04.30 h and 6 and 25 mg l^?1 at 14.00 h, and were considered not limiting to fish growth. The results of this study may help explain observed low fish growth in manure-loaded ponds in monoculture in the tropics.     

Dynamics of floodplain fisheries in Bangladesh, results of 8 years fisheries monitoring in the Compartmentalization Pilot Project

Floodplain fisheries were monitored from 1992 until 2000 in the Compartmentalization Pilot Project in Tangail, Bangladesh. In permanent floodplains about 165 ± 28 kg ha^?1 of fish was caught annually. For seasonal floodplains, this figure was 83 ± 23 kg ha^?1 yr^?1. The fish catch exhibited a strong seasonal variation, with the highest catch in October, when the floodwater recedes towards the river, and the lowest catch during the dry season in April/May. The annual catch varied with the extent of flooding, with high catches in wet years and low catches in dry years. The extent of flooding was quantified through a Flood Index. Plotting the annual yields against this Flood Index provided a significant relation (P < 0.05), confirming the existence of a flood pulse. The fishing effort (f) and the catch‐per‐unit‐effort (CPUE) were significantly related (P < 0.05), whereby the fishing effort increased with increasing CPUE. The results are discussed within the frame of fisheries management in Bangladesh and highlight the need for long‐term data for proper evaluation of fisheries projects and the development of management schemes, and the difficulty of applying standard surplus production models in floodplain fisheries.     

Assessment of the aquaculture subsystem in integrated agriculture–aquaculture systems in Northeast Thailand

A survey of integrated agriculture–aquaculture systems (IAAS) was carried out in four different agroecologies, an irrigated and three rainfed agroecologies (drought‐prone, rainfed lowland and rolling land), in Northeast region of Thailand, of tropical wet:dry climate. Fish culture system of IAAS varied with agroecology but not with the length of farmers' experience in IAAS farming. The size of pond holdings in the rainfed lowland agroecology was estimated to be significantly smaller (P≤0.05) than in the three other agroecologies. The highest average extrapolated gross fish yield of 2.3 tonnes ha^?1 was recorded in the irrigated agroecology and this was significantly higher (P≤0.01) than in the three rainfed agroecologies: drought‐prone (1.1 tonnes ha^?1), rainfed lowland (0.5 tonnes ha^?1) and rolling land (0.4 tonnes ha^?1). Higher fish yield in the irrigated agroecology was associated with longer stocking period and higher amount of pond inputs. Average income of IAAS households from fish also varied across agroecology in a fashion that was noted for yields. However, the farm pond played a pivotal role in the diversification of the farming system in rainfed agroecologies, as it was essentially the only source of water supply for fruit and vegetables production. While fish culture in all agroecologies was a low‐input system, intensification through fertilization of ponds with chemical fertilizers can be envisaged to increase fish production in IAAS in Northeast Thailand.     

Effect of fertilization frequency on pond productivity and fish biomass in still water ponds stocked with Cirrhinus mrigala (Ham.)

Four different fertilization frequencies, namely twice per week, once per week, twice a month and once a month, were used in ponds to assess their effects on nutrient release, pond productivity and fish biomass. All ponds received the same total fertilizer inputs during the experimental period of 60 days (cow dung 208.3 kg ha^?1 week^?1, TSP 9.8 kg ha^?1 week^?1, urea 6.0 kg ha^?1 week^?1). Studies have revealed that the highest values of fish biomass, specific growth rate (SGR), net primary productivity (NPP), plankton population and nutrients were observed in the ponds that were fertilized twice a month. A strong and significant correlation of fertilization frequency was observed with dissolved oxygen, biochemical oxygen demand (BOD), alkalinity, nutrient release, NPP, plankton density (no. L^?1), fish biomass and SGR. The linear relationship between NPP and fish biomass/SGR for all the ponds was strong (r²= 0.88). Sediment chemistry revealed that O‐PO₄, NO₃‐N, organic carbon and electrical conductivity (EC) increased significantly (P<0.05) with a decrease in the frequency of fertilization, while alkalinity and calcium were high in ponds that were fertilized twice a month.     

On the grey mullets of the Nigerian coast,prospects of their culture and results of trials

Mullets have so far been recorded in the brackish water areas only and of the 8 species identified, Liza falcipinnis is the most abundant. Mullet fry (mixed species) are available throughout the year but in greater quantities between March and July. It is estimated that enough fry to stock more than 10 000 ha for polyculture can be collected from the coastal areas. With a view to culturing them in fresh water, it has been possible to acclimatize them to fresh water. This offers good prospects of culturing mullets together with common carp, catfish (Chrysichthys nigrodigitatus) and cichlias (Tilapia sp.)Polyculture trials in brackishwater ponds in Lagos indicate that the natural entry of mullet fry with the tide could result in productions of up to 239 kg ha^?1 year^?1 in addition to that of other species, without supplementary feed or fertilizer. Stocking of mullet fry increased the mullet yield. Experiments indicate that supplementary feed also increases both yield and average size. Predators such as Sphyraena sp. reduce mullet population in fish ponds and also their yield.     

Recruitment control and production of Tilapia aurea (Steindachner) with the predator,Cichlasoma managuense (Günther)

The effects of different stocking rates and ratios of Tilapia aurea (Steindachner) in combination with Cichlasoma managuense (Günther) on tilapia recruitment and production were evaluated in 440 m² ponds. The research was conducted at the National Fisheries Station in El Salvador, Central America.The tilapia A_T value, the total weight of marketable tilapia (14 cm or larger) expressed as a percentage of the total weight of the whole tilapia population, averaged 96 or greater at a stocking ratio of 4:1 (fingerling tilapia: fingerling C. managuense) and at a stocking ratio of 8:1 (fingerling tilapia: adult C. managuense). Tilapia A_T values at a stocking ratio of 8:1 (fingerling tilapia: fingerling C. managuense) ranged from 71–89.Highest estimated annual production of marketable tilapia (3611 kg ha^?1) occurred at the highest stocking rate of 12000 tilapia ha^?1 in populations with an average tilapia A_T value of 98. Greatest weight gain of marketable tilapia (167 g of 1.17 g day^?1) occurred at the lowest stocking rate of 6000 tilapia ha^?1 in populations with an average tilapia A_T value of 99.Estimated annual production of marketable C. managuense ranged from 212–414 kg ha^?1. The average weight gain of marketable fish varied from 48–60 g (0.32–0.40 g day^?1). The average C. managuense, A_T value was 54, ranging from 29–84.The estimated production of marketable fish of both species at stocking rates of 6000, 9000 and 12000 tilapia ha^?1 in populations with tilapia A_T values of 96 or greater averaged 3295, 3290 and 4025 kg ha^?1 per year, respectively.     

Intake and discharge nutrient loads at three intensive shrimp farms

This study was conducted to help provide a framework for Australian regulation of shrimp farm siting and discharges. Monitoring of farm water usage, and intake and discharge water quality was conducted at three commercial intensive shrimp farms, chosen to represent different operating environments, latitudes, cultured species and management styles. Weekly samples were taken over 3 years, for 3–12 months at each farm, to investigate intake and discharge concentrations and loads of total suspended solids (TSS), total nitrogen (TN) and total phosphorus (TP). Mean water exchange was 1.4 ML ha^?1 day^?1 (about 10% day^?1) at the first farm studied and 0.5 ML ha^?1 day^?1 (about 3.6% day^?1) at the others. Farm mean discharge concentration varied as follows: TSS, from 36.9 to 119 mg L^?1; TN, from 2.1 to 3.1 mg L^?1 and TP, from 0.22 to 0.28 mg L^?1. Farm mean intake concentrations were from 11% to 91% of equivalent mean discharge concentration (for TN at Farm B and TSS at Farm C respectively). Mean net discharge loads, related to area of production ponds at each farm, varied as follows: TSS, from 4.8 to 85.7 kg ha^?1 day^?1; TN, from 1 to 1.8 kg ha^?1 day^?1 and TP, from 0.11 to 0.22 kg ha^?1 day^?1. The highest net loads of TSS, TN and TP were all from the farm with the highest water exchange rate, located on a coastal river, and studied during a year of high rainfall with associated poor water quality. These results can be used to help predict likely discharge characteristics for new shrimp farms, and provide a benchmark against which to evaluate future improvements in shrimp farm environmental management.     

Spawning areas and migration patterns in the early life history of Squalius cephalus (Linnaeus, 1758): Use of otolith microchemistry for conservation and sustainable management

1. In the context of the River Rhône restoration programme, the objective of this study was to assess the dispersal and population connectivity of the European chub, Squalius cephalus (Linnaeus, 1758) in a section of the natural, free-flowing part of the lower River Rhône.
2. The elemental water signatures for Sr:Ca and Ba:Ca were measured at seven stations within the river section, including its tributaries and backwaters, to determine whether they could be differentiated by microchemistry. From August to October the signatures differed among three sectors of the study reach: the Rhône; the Ardèche; and the backwaters.
3. The elemental signatures of the otoliths of 178 young-of-the-year (YOY) chub from the stations were measured to assess spawning areas and identify early migratory life histories. Analyses of otolith microchemistry identified the natal origin of 95% of the fish. Sr:Ca signatures of otoliths showed early downstream migration for 30.4% of the YOY chub; however, 70% of the fish recruited relatively close to their spawning origin suggesting a potential inshore retention of fish.
4. The results showed (i) a non-negligible contribution of the tributaries and backwaters in the recruitment of fish into the main channel; and (ii) the ability of chub to migrate over several kilometres during their first few months of life.
5. This study shows that the combination of water and otolith microchemistry analyses of fish growth increases the understanding of fish life history. Moreover, the study revealed that half of the YOY fish from this river section came from the tributaries and the other half came from reproduction in the River Rhône (despite its high anthropization).
6. These methods offer promising future applications of otolith microchemistry for river management in the context of ecological rehabilitation, especially to assess the effectiveness of measures applied in the restoration of floodplain connectivity for riverine fish population conservation.

     

Production performance of sutchi catfish Pangasianodon hypophthalmus S. in restricted feeding regime: effects on gut,liver and meat quality

The experiment was carried out to evaluate the production performance of sutchi catfish, Pangasianodon hypophthalmus in restricted feeding regimes and their effects on gut and liver indices and body composition. Four feeding regimes were evaluated: fed to satiation twice per day (treatment daily feeding); 1‐day food deprivation and 1‐day feeding (treatment 1D‐1F), 2‐day deprivation and 2‐day feeding (treatment 2D‐2F) and 5‐day deprivation and 5‐day feeding (treatment 5D‐5F). Fingerlings (mean weight 37 ± 3 g, mean total length 18 ± 2 cm) were stocked in replicated earthen ponds at a density of 25 000 ha^?1 and cultured for 18 weeks during which commercial diet (33% crude protein) were delivered to apparent satiation on the feeding day according to the treatment. Results showed that the daily feeding and 1D‐1F treatments resulted in similar individual weight gain (515–536 g) and net fish production (10 954–11 387 kg ha^?1) as compared with treatment 2D‐2F (weight gain 309 g; net production 6700 kg ha^?1) or treatment 5D‐5F (weight gain 251 g; net production 5651 kg ha^?1). While fish body protein levels were not affected by food deprivation, lipid contents were lowest in treatments 2D‐2F and 5D‐5F. The study concluded that sutchi catfish could be cultured in alternate‐day feeding regime without any negative effects on production and meat quality of fish resulting in a net profit of USD 2750 ha^?1 pond.     

Variability of fish densities in a small catchment

Abstract— Temporal and spatial variability of fish communities were examined within a 91-km² catchment in central New York over four years. Riffle-dwelling species, slimy sculpin Cottus cognatus , longnose dace Rhinichthys cataractae , and young-of-the-year brown trout Salmo trutta , were more strongly affected by flood and drought than pool-adapted species, adult brown trout, blacknose dace Rhinichthys atratulus , white sucker Catostomus commersoni , and creek chub Semotilus atromaculatus . Canonical correspondence analysis using seven abiotic variables (mean width, residual pool depth, water surface slope, mean Froude number, variance in Froude number, maximum monthly discharge and minimum monthly discharge) separated fish communities among sites and years. The first axis represented a headwater-to-valley gradient; the second axis reflected habitat complexity, based on both geomorphic and hydraulic features. Temporal differences in fish densities were related to hydrological factors. Fish communities throughout the catchment showed similar responses to flood and drought.     

Defining critical habitat conditions for the conservation of three endemic and endangered cyprinids in a Mediterranean intermittent river before the onset of drought

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Effect of supplementary stocking of juvenile brown trout,Salmo trutta,on yield in a Norwegian mountain reservoir

Abstract The effect of supplementary stocking of juvenile (age 0+), hatchery‐reared, brown trout, Salmo trutta L., on annual yields was assessed in a Norwegian mountain reservoir between 1979 and 2007. Fishing was mainly carried out by local fishermen with benthic gillnets. During the study period, annual stocking ranged from 0 to 52 500 fish (19.8 ha^?1). No stocking has been carried out since 1997. Annual yield varied from 1650 to 5653 kg, corresponding to 0.62–2.13 kg ha^?1. Exploitation rate in terms of number of gillnets and mean weight of 6+ fish (age when catchable size was reached) explained 64% of the variability in catches. Stocked fish contributed very little to the yield or catch‐per‐unit‐effort, exhibiting no positive correlation with stocking density. The lack of contribution from stocked fish was probably caused by a competitive bottleneck in the eroded epibenthic zone, causing high juvenile mortality. If stocking continues, it is recommended that fish with body lengths >15–20 cm are used.