Recreational Fish Species Research Articles

Evaluating the conservation benefit of circle hooks for the Atlantic Striped Bass recreational fishery

AbstractObjectiveThe Striped Bass Morone saxatilis is one of the most sought‐after recreational fish species along the US Atlantic coast. Regulations and a strong conservation ethic among anglers make Striped Bass among the most frequently released coastal marine fishes. A recent rule requires anglers to use circle hooks when targeting Striped Bass with natural baits, yet the conservation benefit of this action remains unclear.MethodsWe used acoustic telemetry to monitor the fate of Striped Bass that were recreationally caught with baited hooks (n = 349) and to estimate the influence of various biological (fish size), fishery (fight time, handling time, hook location, bait type, and hook type), and environmental (water temperature and air temperature) variables on postrelease survival.ResultA semi‐quantitative score of fish release condition was the single best predictor of mortality. A broader dataset that included untagged fish (n = 716) was used to identify the best predictors of fish release condition, which included hook location and handling time.ConclusionContrary to expectations, the circle hooks used in this study did not result in lower release mortality than conventional J‐hooks.

Predicting the presence of hypoxic hypolimnia in lakes at large spatial scales

AbstractLakes and reservoirs provide multiple essential ecosystem services to humans, and several of these require the presence of a cool, oxygen‐rich hypolimnion. These ecosystem services include supporting habitat for recreational fish species and the maintenance of a non‐eutrophic state by limiting internal nutrient loading. However, changes in land use and global warming are modifying the thermal structure of lakes worldwide, creating episodic or prolonged periods of hypoxia, changing a lakes ability to deliver certain ecosystem services. Here, we used National Lake Assessment data and machine learning approaches to identify which lake or watershed features determined the presence of a hypolimnion and which contributed to the development of hypoxia. A random forest of 1000 trees predicted the presence of a hypolimnion with 85% accuracy using commonly measured morphometric and physicochemical variables as well as land use. Mean and maximum depths had a disproportionate influence, entirely obscuring the influence of variables commonly associated with lake mixing, such as light penetration and fetch. In contrast, depth had a more restrained role to predict the presence of hypoxia; the latter was predicted with an overall accuracy of 85%, from epilimnetic nitrogen and carbon concentrations. Although the nutrient‐color groups had a minor influence in the random forests, there was a clear trend of increased hypoxia with higher turbidity. Our approach allows for the broad‐scale assessment of lakes with hypolimnia and suggests that increasing eutrophication and browning will promote profundal hypoxia, altering the delivery of certain ecosystems services.

Perfluoroalkyl acid depuration from the edible tissues of a migratory recreationally fished species

Environmental emissions of perfluoroalkyl acids (PFAAs) impact estuarine species and the fisheries that rely on them. Migratory estuarine fishes may be captured for consumption in areas distant to known contaminant sources, but exposure risk depends on how quickly contaminants are depurated. This baseline presents the outcomes from a novel experiment simulating the migration of a popular recreational fish species (Dusky Flathead, Platycephalus fuscus) following environmental exposure to PFAAs, and assessing depuration from edible muscle tissues. Over the 33-day experiment, perfluorooctane sulfonate (PFOS) concentrations declined slowly, with modelling suggesting that concentrations fell below the relevant screening value (5.2 μg kg−1) within ∼558 h (285–1372 h; 90 % CI). Low concentrations (<1.2 μg kg−1) of perfluorohexane sulfonate also depurated rapidly. This study provides useful information for assessing potential exposure risk posed by recreationally targeted fish migrating away from contaminated areas. The experimental design employed has a real-world context that is relevant for future studies.

Impacts of artisanal fishing on the reproductive biology and population structure of tigerfish (Hydrocynus vittatus) in the Ume Basin of Lake Kariba, Zimbabwe

AbstractFisheries studies concerning the related impacts of fishing on the aquatic environment have mostly dealt with industrial fisheries. Concerted large‐scale exploitation can lead to stock declines and potentially species extinction. Hydrocynus vittatus is a piscivore and popular recreational fish species that can grow up to 70 cm fork length and weigh up to 15 kg. Hydrocynus vittatus is also a fish of importance in Lake Kariba as local communities along lake shorelines depend on it for both income and food. There is an insufficient understanding of the impacts of artisanal fishing on tigerfish, H. vittatus population parameters and reproductive biology in Lake Kariba. Hence, this study investigated life history traits and population dynamics of H. vittatus in the Ume Basin of Lake Kariba, north‐eastern Zimbabwe. Scales were used to estimate the age of tigerfish and the Bertalanffy growth curve used to estimate the growth parameters. A gonadal reproductive stage determination index was used to determine sexual maturity and the logistic growth curve was used to estimate size at 50% sexual maturity (L50). Using the gonadal maturation index, the L50 for males was estimated ranging between 120 and 149 mm. On the other hand, L50 reached between 250 and 299 mm in females. Females had a higher average mean length (335 mm), compared to that of males (289 mm). The length‐at‐age data from scales had relatively few outliers and moderate scatter. Parameters for the von Bertalanffy growth curve were (L‐infinity = 641.5, k = 0.517, t0 = 3.07). This study highlighted the negative impacts (male‐biased sex ratio and small size at maturity) that artisanal gillnet fishing has on the population structure and reproductive potential of tigerfish in the Ume Basin of Lake Kariba. These impacts are a direct result of both legal and illegal fishing activities of the fishers operating in the Ume Basin and based at Musamba Fishing Camp. There is, therefore, an urgent need for the regulatory authority, the Matusadona Conservation Trust, to engage the fishers in developing long‐term strategies to reverse the observed unhealthy population status and allow the tigerfish stock to replenish itself.

PFAS and Precursor Bioaccumulation in Freshwater Recreational Fish: Implications for Fish Advisories.

Per- and polyfluoroalkyl substances (PFAS) are a diverse class of fluorinated anthropogenic chemicals that include perfluoroalkyl acids (PFAA), which are widely used in modern commerce. Many products and environmental samples contain abundant precursors that can degrade into terminal PFAA associated with adverse health effects. Fish consumption is an important dietary exposure source for PFAS that bioaccumulate in food webs. However, little is known about bioaccumulation of PFAA precursors. Here, we identify and quantify PFAS in recreational fish species collected from surface waters across New Hampshire, US, using a toolbox of analytical methods. Targeted analysis of paired water and tissue samples suggests that many precursors below detection in water have a higher bioaccumulation potential than their terminal PFAA. Perfluorobutane sulfonamide (FBSA), a short-chain precursor produced by electrochemical fluorination, was detected in all fish samples analyzed for this compound. The total oxidizable precursor assay interpreted using Bayesian inference revealed fish muscle tissue contained additional, short-chain precursors in high concentration samples. Suspect screening analysis indicated these were perfluoroalkyl sulfonamide precursors with three and five perfluorinated carbons. Fish consumption advisories are primarily being developed for perfluorooctane sulfonate (PFOS), but this work reinforces the need for risk evaluations to consider additional bioaccumulative PFAS, including perfluoroalkyl sulfonamide precursors.

Movement patterns of an iconic recreational fish species, mulloway (Argyrosomus japonicus), revealed by cooperative citizen-science tagging programs in coastal eastern Australia

Information on the movements and population structure of an exploited fish species is vital for determining the appropriate spatial scale at which management should occur to ensure sustainable harvesting. However, such information exists for very few exploited species. Large-scale patterns and drivers of movement were examined for an iconic recreational sciaenid species, mulloway (Argyrosomus japonicus), in coastal eastern Australia using an angler-assisted tag-recapture dataset. Over 4300 individuals were tagged and released across 1005 km of coastline over three decades (1988–2017). Six-hundred and fifty-seven individuals were subsequently recaptured at a rate of 15.1% over the same time period. Average time at liberty was 216 (±9) days (range: 0–1954 days), with distances moved ranging from 0 to 355 km. Median movement distance was 4 km, and a large proportion of individuals (73%) were recaptured within 10 km of release locations. Thirty one percent of individuals were recaptured at release locations (< 1 km) and 81% in the same estuary. However, 7% moved distances of > 100 km. Generalised additive modelling revealed that release latitude, body size and time at liberty were significant predictors of distance moved. Greater distances moved were observed for fish tagged at lower latitudes, at larger sizes and over longer periods at liberty. Results indicate that A. japonicus are primarily restricted to small movements (< 10 km) in eastern Australia and display strong site fidelity, despite being capable of movements over larger scales (100s of km). This spatial scale of movement is also much smaller than the current ‘jurisdictional’ scale of management in this region (~1000 km). Assessment and management of A. japonicus in eastern Australia may therefore need to be re-examined considering these findings and potentially undertaken at more localised spatial scales in the future. This study also highlights the importance of citizen science in the cost-effective generation of a sufficiently broad spatio-temporal dataset required to detect the movement patterns revealed here.

Spatial and Temporal Changes in Testis Morphology and Sperm Ultrastructure of the Sportfish Sauger (Sander canadensis)

AbstractThe objective of this study was to assess testicular morphology and spermatozoal structure spatially within the reproductive tract and temporally among seasons in the sauger (Sander canadensis). The testis exists as two separate lobes joined at the urogenital pore and were characterised as unrestricted lobular with seminiferous tubules terminating at the ventral periphery and coalescing dorsally on the main sperm duct. Differences were observed between the pre‐breeding season (November) and breeding season (March), with every stage of spermatogenesis occurring in spermatocysts in pre‐breeding season in contrast to only spermatozoa being present in the tubules and main duct during the breeding season. Longitudinal folds in the main duct epithelium increased in number with increasing proximity to the urogenital pore, greatly increasing epithelial height regardless of season. Sauger spermatozoa consisted of an ovoid head, a midpiece containing 2 – 4 mitochondria incorporated into the head and a single flagellum containing an asymmetrical lateral ribbon. Motile spermatozoa were found throughout the testis during the breeding season. A decrease in sperm concentration was quantified moving proximally, suggesting a hydration effect by the main duct epithelium during the breeding season. These observations fill an important knowledge gap regarding reproductive biology of this impactful recreational fish species.

In the face of climate change and exhaustive exercise: the physiological response of an important recreational fish species.

Cobia (Rachycentron canadum) support recreational fisheries along the US mid- and south-Atlantic states and have been recently subjected to increased fishing effort, primarily during their spawning season in coastal habitats where increasing temperatures and expanding hypoxic zones are occurring due to climate change. We therefore undertook a study to quantify the physiological abilities of cobia to withstand increases in temperature and hypoxia, including their ability to recover from exhaustive exercise. Respirometry was conducted on cobia from Chesapeake Bay to determine aerobic scope, critical oxygen saturation, ventilation volume and the time to recover from exhaustive exercise under temperature and oxygen conditions projected to be more common in inshore areas by the middle and end of this century. Cobia physiologically tolerated predicted mid- and end-of-century temperatures (28–32°C) and oxygen concentrations as low as 1.7–2.4 mg l−1. Our results indicated cobia can withstand environmental fluctuations that occur in coastal habitats and the broad environmental conditions their prey items can tolerate. However, at these high temperatures, some cobia did suffer post-exercise mortality. It appears cobia will be able to withstand near-future climate impacts in coastal habitats like Chesapeake Bay, but as conditions worsen, catch-and-release fishing may result in higher mortality than under present conditions.

Fish Diet Shifts Associated with the Northern Gulf of Mexico Hypoxic Zone

The occurrence of low dissolved oxygen (hypoxia) in coastal waters may alter trophic interactions within the water column. This study identified a threshold at which hypoxia in the northern Gulf of Mexico (NGOMEX) alters composition of fish catch and diet composition (stomach contents) of fishes using fish trawl data from summers 2006–2008. Hypoxia in the NGOMEX impacted fish catch per unit effort (CPUE) and diet below dissolved oxygen thresholds of 1.15 mg L−1 (for fish CPUE) and 1.71 mg L−1 (for diet). CPUE of many fish species was lower at hypoxic sites (≤ 1.15 mg L −1) as compared to normoxic regions (> 1.15 mg L −1), including the key recreational or commercial fish species Atlantic croaker Micropogonias undulatus and red snapper Lutjanus campechanus. Overall, fish diets from hypoxic sites (≤ 1.71 mg L−1) and normoxic sites (> 1.71 mg L−1) differed. Fish caught in normoxic regions consumed a greater mass of benthic prey (ex. gastropods, polychaetes) than fish caught in hypoxic regions. Hypoxia may increase predation risk of small zooplankton, with observations of increased mass of small zooplankton in fish stomachs when bottom hypoxia was present. Changes in contributions of small zooplankton and benthic prey to fish diet in hypoxic areas may alter energy flow in the NGOMEX pelagic food web and should be considered in fishery management.

Headwater Streams and Wetlands are Critical for Sustaining Fish, Fisheries, and Ecosystem Services

Headwater streams and wetlands are integral components of watersheds that are critical for biodiversity, fisheries, ecosystem functions, natural resource‐based economies, and human society and culture. These and other ecosystem services provided by intact and clean headwater streams and wetlands are critical for a sustainable future. Loss of legal protections for these vulnerable ecosystems would create a cascade of consequences, including reduced water quality, impaired ecosystem functioning, and loss of fish habitat for commercial and recreational fish species. Many fish species currently listed as threatened or endangered would face increased risks, and other taxa would become more vulnerable. In most regions of theUSA, increased pollution and other impacts to headwaters would have negative economic consequences. Headwaters and the fishes they sustain have major cultural importance for many segments of U.S. society. Native peoples, in particular, have intimate relationships with fish and the streams that support them. Headwaters ecosystems and the natural, socio‐cultural, and economic services they provide are already severely threatened, and would face even more loss under the Waters of the United States (WOTUS) rule recently proposed by the Trump administration.

Combining data sources to elucidate spatial patterns in recreational catch and effort: fisheries-dependent data and local ecological knowledge applied to the South Florida bonefish fishery

Spatial data are key to fishery management; however, most often the spatial distribution of marine populations and fishing dynamics are poorly documented, especially for recreational fish species. The combination of fisheries-dependent data (FDD) obtained from logbooks, and local ecological knowledge (LEK) gathered from key stakeholders could be a powerful approach to inform data gaps in data-limited fisheries. In this study, we used both FDD from guides’ catch reports and LEK using an online survey and key-informant interviews to reconstruct the spatial changes in bonefish (Albula vulpes) catch and fishing effort throughout South Florida over the past 35–40 years, and better understand the extent and spatial patterns of the bonefish decline described in previous studies. Although anglers perceived a decline of bonefish numbers across all fishing areas (26 to 53% drop across Biscayne Bay, the Florida Keys, and Florida Bay), the start of the bonefish decline in Florida Bay resulted in the highest drop in bonefish number (53%); thus, indicating both regional and localized decline events affecting bonefish abundance. Within Florida Bay, LEK and FDD concurred with an initial drop in bonefish at Inner Bay, followed by a greater magnitude of decline at Outer Bay. Metrics of effort derived from the survey and interviews depicted a shrinkage and aggregation in the spatial distribution of fishing and a shift of fishing activities toward the Lower Keys. In sum, the spatiotemporal patterns of catch and effort obtained from LEK and FDD allowed us to understand where, when and how this data-limited species declined in South Florida.

Diet of Striped Bass and Muskellunge Downstream of a Large Hydroelectric Dam: A Preliminary Investigation into Suspected Atlantic Salmon Smolt Predation

AbstractTop predators, such as the Striped Bass Morone saxatilis and Muskellunge Esox masquinongy, can impact food webs and alter ecosystem structure through the regulation of prey populations. Within the Saint John River, New Brunswick, Canada, both predators have long been hypothesized to impart significant mortality on smolts of the endangered Atlantic Salmon Salmo salar. As a consequence, current management practices entail euthanizing Muskellunge (an introduced species) that enter fish passage facilities along the Saint John River. Furthermore, the recovery and protection of a native Striped Bass population have largely been ignored. To assess seasonal diet, gastric lavage was performed on Striped Bass (n = 244) and Muskellunge (n = 96) captured in the downstream proximity of the Mactaquac Dam from April to November 2016. Clupeids dominated the stomach contents by number (92% for Striped Bass; 49% for Muskellunge) and mass (71% for Striped Bass; 96% for Muskellunge). Other prey species included White Perch Morone americana, Yellow Perch Perca flavescens, American Shad Alosa sapidissima, and American Eels Anguilla rostrata. No Atlantic Salmon smolts or other regionally recognized recreational fish species were identified in any of the stomach samples (n = 340) examined. Concurrently, this study observed little temporal overlap between the smolt migratory period and the arrival of Striped Bass to the Mactaquac Dam. Some Striped Bass (n = 33) were observed to be in spawning condition, releasing eggs and milt when handled, although reproduction by this species in the Saint John River was thought to have ceased long ago.

Evaluating spatial and temporal variability in growth and mortality for recreational fisheries with limited catch data

Understanding the spatial and temporal variability in life-history traits among populations is essential for the management of recreational fisheries. However, valuable freshwater recreational fish species often suffer from a lack of catch information. In this study, we demonstrated the use of an approach to estimate the spatial and temporal variability in growth and mortality in the absence of catch data and apply the method to riverine smallmouth bass (Micropterus dolomieu) populations in Pennsylvania, USA. Our approach included a growth analysis and a length-based analysis that estimates mortality. Using a hierarchical Bayesian approach, we examined spatial variability in growth and mortality by assuming parameters vary spatially but remain constant over time and temporal variability by assuming parameters vary spatially and temporally. The estimated growth and mortality of smallmouth bass showed substantial variability over time and across rivers. We explored the relationships of the estimated growth and mortality with spring water temperature and spring flow. Growth rate was likely to be positively correlated with these two factors, while young mortality was likely to be positively correlated with spring flow. The spatially and temporally varying growth and mortality suggest that smallmouth bass populations across rivers may respond differently to management plans and disturbance such as environmental contamination and land-use change. The analytical approach can be extended to other freshwater recreational species that also lack of catch data. The approach could also be useful in developing population assessments with erroneous catch data or be used as a model sensitivity scenario to verify traditional models even when catch data are available.

Recreational charter fishery attributes and variation in key species catches and discards: Resource management considerations

Strategic long-term sampling programmes that deliver recreational catch, effort and species demographic data are required for the effective assessment and management of recreational fisheries and harvested organisms. This study used a spatially and temporally stratified observer programme to examine variation in the rates, quantities and lengths of retained and discarded catches of key species in a recreational charter fishery. Geographic region, but not season, significantly influenced catch rates of key demersal species, being driven by temporally persistent latitudinal clines in environmental conditions influencing species distributions. There was considerable trip-to-trip variation in catch rates that were attributed to localised differences in fishing operations, locations, environmental conditions and client preferences. Broad trends in retained and discarded catch rates were nevertheless, similar across different fishing effort standardisations (per-trip, per-hour, per-client, per-client/fished hour), demonstrating that the coarsest unit of effort could be used in fishery assessments. Discard rates of organisms were variable and driven by a combination of mandated legal lengths, individual client and operator preferences for particular species and sizes of organisms, and not due to attainment of catch quotas or high-grading. This study has identified important fishery attributes that require consideration in assessing charter fisheries and stocks of recreational fish species.

The effects of measurement uncertainty on spatial characterisation of recreational fishing catch rates

Accurate mapping of catch rates of fish species is important for identifying their abundances and locations, and for monitoring their population changes. However, the use of imprecise fishing survey data may influence mapping and delineation of locations with high catch rates. We evaluated the incorporation of measurement uncertainty in recreational catch rate data for three important recreational fish species with different behavioural and distributional characteristics. The study combined a soft indicator kriging approach that uses a logistic function transformation and p-field simulation to determine the effect of measurement uncertainty on catch rate mapping and fishing area delineation. The results suggest that measurement uncertainty can influence the degree of spatial autocorrelation and the precision of kriging estimation. In addition, measurement uncertainty was found to influence the probability of classifying a location as either being a high or low catch rate zone. In general, the incorporation of the measurement uncertainty improves the ability to draw valid conclusions about the estimation results, which may influence any decision regarding the delineation of areas of abundance for spatial management. The use of a soft indicator kriging approach is a promising tool for catch rate mapping, in particular for survey data with class-specific patterns of spatial continuity.

Multi year observations reveal variability in residence of a tropical Demersal Fish, Lethrinus nebulosus: implications for spatial management.

Off the Ningaloo coast of North West Western Australia, Spangled Emperor Lethrinus nebulosus are among the most highly targeted recreational fish species. The Ningaloo Reef Marine Park comprises an area of 4,566 km2 of which 34% is protected from fishing by 18 no-take sanctuary zones ranging in size from 0.08–44.8 km2. To better understand Spangled Emperor movements and the adequacy of sanctuary zones within the Ningaloo Reef Marine Park for this species, 84 Spangled Emperor of a broad spectrum of maturity and sex were tagged using internal acoustic tags in a range of lagoon and reef slope habitats both inside and adjacent to the Mangrove Bay Sanctuary zone. Kernel Utilisation Distribution (KUD) was calculated for 39 resident individuals that were detected for more than 30 days. There was no relationship with fish size and movement or site fidelity. Average home range (95% KUD) for residents was 8.5±0.5 km2 compared to average sanctuary zone size of 30 km2. Calculated home range was stable over time resulting in resident animals tagged inside the sanctuary zone spending ∼80% of time within the sanctuary boundaries. The number of fish remaining within the array of receivers declined steadily over time and after one year more than 60% of tagged fish had moved outside the sanctuary zone and also beyond the 28 km2 array of receivers. Long term monitoring identified the importance of shifting home range and was essential for understanding overall residency within protected areas and also for identifying spawning related movements. This study indicates that despite exhibiting stable and small home ranges over periods of one to two years, more than half the population of spangled emperor move at scales greater than average sanctuary size within the Ningaloo Reef Marine Park.

Seasonal distribution of Trachurus mediterraneus (Steindachner, 1868) in the Golden Horn Estuary, İstanbul

Seasonal changes in the distribution of an important commercial and recreational fish species, Trachurus mediterraneus (Steindachner, 1868), from the family Carangidae were investigated in the Golden Horn Estuary of İstanbul. Environmental conditions were also considered to evaluate distributional patterns in the region. Sampled fish size ranged between 7.5 and 20.1 cm in total length and 3.4 and 86.2 g in total weight during the sampling period. Adult individuals (>12.5 cm) preferred not to be in the estuary during the summer period, while only immature adults were found with a 7.5-12.5 cm total length size range from May to August 2009. It was observed that on a regional basis this species was only found at the entrance of the Golden Horn. Environmental parameters such as surface temperature, salinity, and dissolved oxygen values did not display significant correlations with its distribution throughout the study period. However, chlorophyll a and Secchi disk values displayed significant negative correlations with the distribution of immature adults in the Golden Horn.

Spatial variability in selenium and mercury interactions in a key recreational fish species: Implications for human health and environmental monitoring

Selenium’s (Se) protective effects against mercury (Hg) toxicity have been demonstrated; however, this is seldom considered in health assessments, where dietary exposure is still evaluated by Hg concentration alone. Se:Hg ratios and selenium health benefit values (Se HBVs) offer a more comprehensive seafood safety model. Here we describe total mercury (THg), methylmercury (MeHg) and Se concentrations in fish from a Hg-polluted estuary. Spatial variation in THg, MeHg and Se was evident, though all regions maintained Se:Hg ratio values >1. Se HBV varied between regions and in one region mean negative values (−5.17) were evident. This study provides the first evidence that quoting a single all-encompassing Se HBV is not appropriate when species demonstrate strong site fidelity. It highlights the need for research into Se–Hg relationships in environments with established Hg pollution and reinforces the assertion that Se concentration be considered in assessments of human health risk to Hg exposure.

Linking environmental flows with the distribution of black bream Acanthopagrus butcheri eggs, larvae and prey in a drought affected estuary

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 483:273-287 (2013) - DOI: https://doi.org/10.3354/meps10280 Linking environmental flows with the distribution of black bream Acanthopagrus butcheri eggs, larvae and prey in a drought affected estuary Joel Williams1,*, Greg P. Jenkins1,2, Jeremy S. Hindell3, Stephen E. Swearer1 1Department of Zoology, University of Melbourne, Parkville, Victoria 3010, Australia 2Fisheries Research Branch, Department of Primary Industries, Queenscliff, Victoria 3225, Australia 3Arthur Rylah Institute, Department of Sustainability and Environment, Heidelberg, Victoria 3084, Australia *Email: jwi@unimelb.edu.au ABSTRACT: Estuaries are under threat from changes in freshwater flows resulting from anthropogenic impacts and climate change, with unknown consequences for estuarine biota. In the past decade, significant rain deficits in south-eastern Australia have coincided with a decrease in commercial catches of black bream Acanthopagrus butcheri, an important commercial and recreational fish species that spawn in estuaries. We investigated the temporal and spatial distribution of black bream eggs and larvae, and copepods—preferred larval prey—in relation to the hydrology of the Mitchell River, a drought-stricken tributary of Australia’s largest estuarine lagoon system. We collected eggs, larvae, zooplankton and water quality data at multiple depths from 8 sampling sites over 7 fieldtrips from August to December 2008. The hydrology of the Mitchell River during this study was highly complex and influenced by freshwater flow. Spatial coupling between black bream larvae, copepods and the halocline was observed in the upper estuary. Nauplii of the copepod Gladioferens pectinatus, an important prey species for larval fish, dominated the zooplankton assemblage (>80%) and larval gut contents. This study demonstrates that freshwater flows and the generation of salinity stratification have a large influence on the size of suitable habitat for larval bream. Drought, water abstraction and climate change could potentially reduce flows to the point where salinity stratification in the estuary is diminished, resulting in declines in replenishment to populations of black bream and possibly other estuarine-dependent fish. KEY WORDS: Ichthyoplankton · Larvae · Prey · Copepod · Stratification · Zooplankton · Halocline Full text in pdf format PreviousNextCite this article as: Williams J, Jenkins GP, Hindell JS, Swearer SE (2013) Linking environmental flows with the distribution of black bream Acanthopagrus butcheri eggs, larvae and prey in a drought affected estuary. Mar Ecol Prog Ser 483:273-287. https://doi.org/10.3354/meps10280 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 483. Online publication date: May 30, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Quantifying selection differentials caused by recreational fishing: development of modeling framework and application to reproductive investment in pike (Esox lucius).

Methods for quantifying selection pressures on adaptive traits affected by size-selective fishing are still scarce, and none have as yet been developed for recreational fishing. We present an ecologically realistic age-structured model specifically tailored to recreational fishing that allows estimating selection differentials on adaptive life-history traits. The model accounts for multiple ecological feedbacks, which result in density-dependent and frequency-dependent selection. We study selection differentials on annual reproductive investment under size-selective exploitation in a highly demanded freshwater recreational fish species, northern pike (Esox lucius L.). We find that recreational angling mortality exerts positive selection differentials on annual reproductive investment, in agreement with predictions from life-history theory. The strength of selection increases with the intensity of harvesting. We also find that selection on reproductive investment can be reduced by implementing simple harvest regulations such as minimum-size limits. The general, yet computationally simple, methods introduced here allow evaluating and comparing selection pressures on adaptive traits in other fish populations and species, and thus have the potential to become a tool for evolutionary impact assessment of harvesting.