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Fisheries Management and Ecology

Wiley Online Library : Fisheries Management and Ecology

Published: 2018-02-01T00:00:00-05:00


An assessment of catches of shore sport fishing competitions along the coast of the Maltese Islands: Implications for conservation and management


Competitive shore-based sport fishing is a popular recreational activity in the Maltese Islands. However, prior to this study, no scientific research surveys had been carried out during sport fishing competitions to investigate catches. Collaboration with Maltese sports fishermen was developed to target sustainable management. Recreational fishing catches were recorded between July 2012 and December 2015 by means of 1,633 roving-access creel surveys, conducted during 79 sport fishing competitions, totalling a fishing effort of 7,548 hr. A total of 29,916 fish belonging to 80 species from 26 different families were caught at a mean catch-per-unit-effort (CPUE) of 4.16 fish angler/hr (SD ± 3.79) and 0.18 kg angler/hr (SD ± 0.17) but with seasonal variation. Catch-and-release practices were implemented by all Maltese sport fishing clubs, however, the mean mortality rate stood at 35.5% (SD ± 42.1), indicating that more effort is required to improve survival of fish. The study outcomes provide conservation recommendations.

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.

Drivers of the upper River Amazon giant catfish fishery


Artisanal fishers of the upper reaches of the Amazon River use a variety of tactics to catch giant Brachyplatystoma catfish species: Brachyplatystoma vaillantii Valenciennes, Brachyplatystoma rouseauxii (Castelnau) and Brachyplatystoma filamentosum (Lichtenstein). These catfish are migratory, caught with different gears, by different communities, and influenced by temporal and spatial changes in river conditions. Facing these factors, it was hypothesised that the catfish fishery yields in the headwaters of the Amazon are determined by fishing tactics efficiency, riverscape features and governance basis. Data on catfish yields were collected from two contrasting riverscapes (rapids and floodplains) in the most important Amazonian affluent in Colombia—the Caquetá River. Results indicated that: (1) catfish yield was strongly associated with fishing effort in both riverscapes, (2) seasonal drivers play an essential influence in the high rapids reach, and river level in the low floodplain reach, (3) community strategies affected yield, although the effect is different depending on the gear used as the environment profile affects enforcement. Based on the results, it was concluded that efficient upstream management of these species should combine specific measures for each riverscape with an integrated approach to the river production system that considers catfishes longitudinal migrations and the growth overfishing occurring in the Amazon estuary.

Do estuaries with different fishing activity have different fish assemblages and populations?


Commercial and recreational fishing have impacts on fish assemblages and populations, but does their combined fishing pressure result in different fish assemblages in estuaries with only one type of fishing activity? This pilot study tested the model that estuaries with only one type of fishing activity have fewer impacts on fish assemblages and populations than estuaries with more than one type because the fishing pressure in the latter will be greater and results in different fish assemblages and taxa. Fish assemblages and populations, including diversity, abundance and size, did not significantly differ despite exposure to different fishing activities. Detecting differences in fish assemblages in estuaries associated with different fishing activities is difficult as smaller scale spatial and temporal factors have a significant influence on the patterns observed. This highlights the importance of paying close attention to the design of sampling programmes. The nested design of this study enabled identification of where greater effort is required to increase the capacity to detect differences. Recommendations for future studies are provided.

Diel habitat selection of largemouth bass following woody structure installation in Table Rock Lake, Missouri


Largemouth bass Micropterus salmoides (Lacepède) use of installed habitat structure was evaluated in a large Midwestern USA reservoir to determine whether or not these structures were used in similar proportion to natural habitats. Seventy largemouth bass (>380 mm total length) were surgically implanted with radio transmitters and a subset was relocated monthly during day and night for one year. The top habitat selection models (based on Akaike's information criterion) suggest largemouth bass select 2–4 m depths during night and 4–7 m during day, whereas littoral structure selection was similar across diel periods. Largemouth bass selected boat docks at twice the rate of other structures. Installed woody structure was selected at similar rates to naturally occurring complex woody structure, whereas both were selected at a higher rate than simple woody structure. The results suggest the addition of woody structure may concentrate largemouth bass and mitigate the loss of woody habitat in a large reservoir.

Deep hooking, landing success and gear loss using inline and offset circle and J hooks when bait fishing for white sturgeon


The issue of deep hooking is of concern in white sturgeon, Acipenser transmontanus Richardson, fisheries because nearly all anglers use bait with a stationary presentation on the river bottom to catch them, and bait fishing is often associated with higher instances of deep hooking and hooking mortality. Deep hooking rates, landing success and catch rates were investigated for anglers bait fishing for white sturgeon using circle and J hooks with inline and offset alignments fished with both active and passive hook-setting methods. Anglers hooked 578 white sturgeon and landed 508 fish, ranging in size from 60 to 316 cm total length (mean = 137 cm). Deep hooking rates averaged 0.6% and did not differ between hook types, hook alignments or hook-setting methods. Landing success (the proportion of hooked sturgeon that were successfully landed) and catch rates were also equivalent between hook types, hook alignments and hook-setting methods; landing success averaged 88% and catch rates averaged 0.27 fish/hr. Results of this study indicate that deep hooking is rare when angling for white sturgeon using standard bait-fishing gear regardless of hook-setting method or whether circle or J hooks were used; regulations restricting hook type in sturgeon bait fisheries are therefore unwarranted.

Issue Information


Investigating the genetic structure of trout from the Garden of Ninfa (central Italy): Suggestions for conservation and management


Mediterranean populations of brown trout (Salmo trutta L. complex) have lost a large part of their genetic distinctiveness, mostly due to massive restocking, and the waters of the Gardens of Ninfa (province of Latina, central Italy, Site of Community Importance since 2013) are regarded as one of a few potential reservoirs of autochthonous trout lineages in the Tyrrhenian drainage of the Italian peninsula. In this study, nuclear and mitochondrial markers were used on brown trout samples from Ninfa to estimate non-Mediterranean influence in the population gene pool, potential changes of genetic structure over time and genetic relationships with other sites known (or suspected) to host native trout gene pools. Striking changes in both microsatellite and mtDNA allele frequencies over a 9-year time span were found and provided evidence of unrecorded stocking from the nearby Lake Fibreno. Results are analysed in the light of potential ecological consequences of such events on a longer time scale and provide a scientific background for fisheries management and conservation programmes in the area.

Fishway with two entrance branches: Understanding its performance for potamodromous Mediterranean barbels


Many fish passes have been built across the world in recent years. This study analyses the performance of a modified type of pool and weir fishway with two access branches, using passive integrated transponder telemetry. A circum-Mediterranean barbel, Luciobarbus bocagei (Steindachner, 1864), was chosen as the target species. Both hydraulic values (flow and volumetric energy dissipation) and biological parameters (attraction, entrance and passage success) were measured in the fishway, these being related to the environmental variables affecting upstream fish movement. Flow discharge, water temperature and atmospheric pressure were important for fish entering the fishway. There was no preference between path routes, even though the main discharge was concentrated in the turbine channel. This type of fishway design could be an alternative for the conservation of fish populations where multiple fish approach options are possible.

Do habitat measurements in the vicinity of Atlantic salmon (Salmo salar) parr matter?


Atlantic salmon, Salmo salar L., parr habitat characterisation is usually performed by in situ measures of key environmental variables taken at the exact fish location if the fishing gear allows precise pinpointing of this location, or in large sampling sections covering a river reach or mesohabitat, often ignoring variability in the immediate vicinity around individual fish. These data may be critically important in the development and validation of habitat preference models. The influences of seven increasing distances of measures, the variation of the number of considered measures and the depth of velocity measurement (bottom or 0.6 of the depth) in the calculations of HSI (Habitat Suitability Index) from a multiple-experts fuzzy model of Atlantic salmon parr habitat were tested. When a parr was present, six measures collected in a 50-cm radius around the fish to provide an average measure as input data and velocity measured at 60% of the depth gave the highest HSI values. These results show some potential for the use of an intermediate study scale, between micro- and mesohabitat, and questions how fish habitat conditions are currently measured.

Catch-related fish injury and catch efficiency of stow-net-based fish recovery installations for fish-monitoring at hydropower plants


Hydropower-related damage to fish remains a great challenge, making objective monitoring of turbine-related fish injury a necessity. The catch of fish at turbine outlets is currently realised by net fishing, but potential catch-related injuries are largely unknown. Catch efficiency and fish-friendliness in relation to fish handling, exposure time, floating debris and fish biomass of four fish recovery installations were assessed using seven species. Highly species-specific lethal and sublethal effects were observed. Exposure time had the strongest effects on catch-related damage, being up to 150-fold increase after 12 hr compared to 1 hr. Up to 84% mortality occurred in the most sensitive species Thymallus thymallus L. Besides exposure time, higher current speed and biomass within the net resulted in greater fish damage. To minimise catch-related effects, keeping emptying periods <1–2 hr and considering the effects of current speed, fish and debris biomass are crucial to increase data comparability among studies.

Fish invasion in the river systems of Guangdong Province, South China: Possible indicators of their success


Although a large number of fish species have been introduced into Guangdong Province in Southern China, a few species, such as tilapia (Tilapia spp.), North African catfish Clarias gariepinus Burchell, mrigal carp, Cirrhinus mrigala (Bloch) and the sucker mouth catfish (Hypostomus sp.), have established natural populations and can be considered “successful invaders” in large rivers. The specific mechanisms underlying these contrasting results among different introduced fish species remain understudied. The relationship between multiple abiotic–biotic factors and the success of four invasive species was investigated using survey data for the Guangdong Province river ecosystem. In contrast to previous studies that have considered species-specific traits, the focus was on economic, ecological and anthropogenic factors to predict invasion success. Four main predictive indicators were found: (1) successful invaders were of low or no commercial value; (2) successful invaders tolerated a wide range of environmental conditions, including poor water quality; (3) biodiversity loss accelerated the growth of non-native populations; (4) human disturbance facilitated population growth and spread of invasive fish species. To lessen the impacts of invasive fish species, the selection of breeding species and breeding areas, maintenance of water quality and reduction in water pollution, protection of the diversity of fish species and reduction of human interference should be addressed.

Response of estuarine consumer communities following the stocking of a juvenile penaeid (Penaeus plebejus) over two consecutive years


Research programmes that monitor and evaluate the impact of stocking activities are essential to quantify effects of stocking and provide information for adaptive management of future releases. The consumer communities in two estuaries stocked with 5.8 million post-larvae eastern king prawn Penaeus plebejus (Hess) were monitored, both before and after stocking, and relative to two similar reference estuaries. Following stocking, there was evidence of increases in the abundances of prawns within stocked estuaries. Communities in all four estuaries showed significant levels of variation over time as well as among the systems themselves. Changes in overall diversity were similarly observed. The presence or absence of vegetation and other seasonal effects were found to explain most of the observed variation in the community assemblage, while prawn stocking appeared to have a little detectable influence. While this study points to minimal impacts of prawn stocking on the consumer community at the densities used, research into potential shifts in resource use by competitors and the growth and survival of prawns is required to fully understand post-release changes in stocked systems.

Effect of fishing effort on catch rate and catchability of largemouth bass in small impoundments


Largemouth bass Micropterus salmoides (Lacepède) catch rates decline with sustained fishing effort, even without harvest. It is unclear why declines in catch rate occur, and little research has been directed at how to improve catch rate. Learning has been proposed as a reason for declining catch rate, but has never been tested on largemouth bass. If catch rate declines because fish learn to avoid lures, periods of no fishing could be a management tool for increasing catch rate. In this study, six small impoundments with established fish populations were fished for two May to October fishing seasons to evaluate the effect of fishing effort on catch rate. Closed seasons were implemented to test whether a 2-month period of no fishing improved catch rates and to determine whether conditioning from factors other than being captured reduced catch rate. Mixed-model analysis indicated catch rate and catchability declined throughout the fishing season. Catch rate and catchability increased after a 2-month closure but soon declined to the lowest levels of the fishing season. These changes in catch rate and catchability support the conclusion of learned angler avoidance, but sustained catchability of fish not previously caught does not support that associative or social learning affected catchability.

Using angling and electric fishing to estimate smallmouth bass abundance in a river


Estimating abundance is fundamental to effective fishery management but can be challenging in a river where spatial and temporal heterogeneity may preclude the consistent use of a single sampling gear and different gears have differing size selectivity and capture probabilities of fish. In this study, the number of smallmouth bass, Micropterus dolomieu Lacepède, was estimated based on mark–recapture data from angling and boat electric fishing in a 4.2-km regulated section (mean width = 115 m) of the Broad River, South Carolina, USA. Closed-population capture–mark–recapture models were fit in the Bayesian hierarchical modelling framework with an estimated number of 2,380 fish (95% credible interval: 1,578–3,693) over 200 mm TL, although simulations indicated that abundance would be slightly overestimated (<20%) when two gears selected for different individuals. Integrating two gear types into a mark–recapture study can provide a method for assessing abundance in spatially or temporally heterogeneous habitats.