Fisheries Surveys Research Articles

Field and DNA-barcode based surveys reveal evidence of rare endemic fishes in the Rufiji River Basin

Endemic fish species have long supported the livelihoods of local communities in the Rufiji River Basin (RRB). However, destructive fishing practices have led to a concerning decline in endemic fish stocks. To assess these changes, this study employed key informant interviews, focus group discussions (FGDs), and fishery surveys to assess the historical and contemporary distribution of endemic fishes within the RRB. DNA barcoding was also used to verify species identities. Out of 37 reported fish species, 33 species (54.55% endemic and 45.45% exotic to RRB) were confirmed through DNA barcoding and morphological characteristics. About 5 species including, Heterobranchus longifilis, Citharinus congicus, Labeo congoro, Mormyrus longirostris, and Labeobarbus leleupanus were rarely found in the field, despite being classified as Least Concern by IUCN. Additionally, five species that were reported to be present in the RRB by experienced fishers were not captured during sampling. This highlights the need for validation of the existence of such species through eDNA metabarcoding. Moreover, due to the rarity of some species in the area, their IUCN assessment should be revisited.

Sources and transport pathways of trace metals to the outer continental shelf off South Carolina and Georgia, USA revealed from the otoliths of moray eels

Trace metal concentrations in otoliths of spotted moray eels (Gymnothorax moringa), non-migratory residents of hard bottom reefs at depths of ∼30–70m along the outer shelf adjacent to South Carolina and Georgia, were analyzed to determine if results provide insights into trace metal sources and transport processes in this dynamic region of the shelf. Li and Mg appear to reflect exposure to local sea water circulated through adjacent porous rock outcrops where the eels reside. Concentrations of Mn, V, Cu, and Zn in otoliths appear to be associated with deep water upwelled along the shelf break. Based on 30 years of water temperature data from fishery surveys, Scamp Ridge, located at 32.30 N at a depth of ∼50m, has significantly lower summertime bottom temperature than elsewhere along the shelf edge, indicating locally enhanced upwelling at that location. The highest levels of Cu and Zn and the lowest of Mn and V were also found in otoliths of eels collected in the vicinity of Scamp Ridge. These results indicate that otolith chemistry in eels can reveal fine-scale structure of water mass inputs to the outer shelf of the southeastern US coast.

Habitat for Coilia nasus in southern Zhejiang Province, China, based on a maximum entropy model

As an important fishery resource and endangered species, studying the habitat of Coilia nasus (C. nasus) is highly significant. This study used fishery survey data from southern Zhejiang coastal waters from 2016 to 2020, employing a maximum entropy model (MaxEnt) to map the habitat distribution of C. nasus. Model performance was evaluated using two metrics: the area under the curve (AUC) of the receiver operating characteristic curve for the training and test sets and true skill statistics (TSS). This study aimed to predict the habitat distribution of C. nasus and explore how environmental variables influence habitat suitability. The results indicated that the models for each season had strong predictive performance, with AUC values above 0.8 and TSS values exceeding 0.6, indicating that they could accurately predict the presence of C. nasus. In the study area, C. nasus was primarily found in brackish or marine waters near bays and coastal islands. Among all environmental factors, salinity (S) and bottom temperature (BOT) had the highest correlations with habitat distribution, although these correlations varied across seasons. The findings of this study provide empirical evidence and a reference for the conservation and management of C. nasus and for the designation of its protected areas.

An Improved YOLOv8n Used for Fish Detection in Natural Water Environments.

To improve detection efficiency and reduce cost consumption in fishery surveys, target detection methods based on computer vision have become a new method for fishery resource surveys. However, the specialty and complexity of underwater photography result in low detection accuracy, limiting its use in fishery resource surveys. To solve these problems, this study proposed an accurate method named BSSFISH-YOLOv8 for fish detection in natural underwater environments. First, replacing the original convolutional module with the SPD-Conv module allows the model to lose less fine-grained information. Next, the backbone network is supplemented with a dynamic sparse attention technique, BiFormer, which enhances the model's attention to crucial information in the input features while also optimizing detection efficiency. Finally, adding a 160 × 160 small target detection layer (STDL) improves sensitivity for smaller targets. The model scored 88.3% and 58.3% in the two indicators of mAP@50 and mAP@50:95, respectively, which is 2.0% and 3.3% higher than the YOLOv8n model. The results of this research can be applied to fishery resource surveys, reducing measurement costs, improving detection efficiency, and bringing environmental and economic benefits.

Mysis segerstralei, an unexpected but important prey for resident Arctic charr (Salvelinus alpinus) in a Svalbard lake

Mysis segerstralei is distributed over a wide geographic area and in habitats with a variety of salinity conditions, including marine and brackish waters around Svalbard. The species has seldom been found in freshwater lakes, and the discovery of M. segerstralei in Lake Pulmankijärvi at the border between Northeastern Norway and Finland, may represent the single known freshwater occurrences in western Europe. Svalbard lake systems are characterized by very low water temperatures, long-term ice cover, and low levels of nutrients. Food is thus limited, and chironomids generally dominate the stomach contents in Arctic charr, the only freshwater fish species on Svalbard. Based on several surveys in more than 30 of Svalbard lakes over many decades, M. segerstralei has only been found as food for Arctic charr in Lake Vårfluesjøen. In a later fishery survey, we studied the diet of Arctic charr in this lake. The stomach contents from Arctic charr sampled in the profundal habitats were dominated by M. segerstralei, but the species was also among the most frequent prey items in the littoral and pelagic habitats. This unexpected occurrence of M. segerstralei demonstrates the high importance of mysids even in a low-productive, High Arctic lake.

Otolith chemistry reveals ontogenetic movement of the Antarctic toothfish (Dissostichus mawsoni) in the Amundsen Sea polynya, Antarctica

The Amundsen Sea polynya is one of the richest areas of primary productivity in Antarctica. The Antarctic toothfish (Dissostichus mawsoni, TOA) is a commercially valuable circum-Antarctic fish that undertakes ontogenetic movements on the continental shelf. However, the movement and distribution of this species remain unclear in the polynya, especially in the data-poor Amundsen Sea polynya. Along with hydrological and fishery survey data in the Amundsen Sea polynya, the otolith chemistry of TOA from three areas along the ice shelf of the Dotson–Getz Trough was analyzed to explore the movement pattern of this species. The elemental composition deposited during early life in the otolith core did not show significant differences, indicating that TOA in the Amundsen Sea polynya probably experienced a similar hydrological environment at the early life stage or might originate from the same spawning ground. However, the elemental composition deposited at the otolith edge showed that SrCa−1 and LiCa−1 differ in otolith chemistry between areas along the Amundsen Sea coast. In conjunction with additional data from the fish sampled in these areas, this study reveals that TOA show an ontogenetic movement from westward along the ice shelf in the Amundsen Sea polynya. A deeper area (with a depth of over 1000 m) in the west box provides a fish pool for TOA, which needs to be conserved in the fishery management of toothfish populations.

Analysis of Fishing Vessel Accidents and Suggestions for Safety Policy in South Korea from 2018 to 2022

Commercial fishing, one of the most dangerous sectors globally and, particularly, in South Korea, faces fatal accident rates significantly exceeding other industries, and an urgent improvement in safety measures is necessary to reduce these numbers effectively. The main objective of this study is to analyse fishing vessel accidents in South Korea and present the direction of safety policy for fishing vessels based on the lessons learnt from previous accidents, and, ultimately, to contribute to reduce fishing vessel accidents. For this purpose, we have analysed the marine accident data from the last five years provided by the Korea Maritime Safety Tribunal (KMST), the statistical yearbook of oceans and fisheries provided by the Ministry of Oceans and Fisheries (MOF), and the statistical survey of marine fisheries provided by the Korean Statistical Information Service (KOSIS), using both quantitative and qualitative approaches. After thorough review and analysis of the accident data, we have proposed seven suggestions for the direction of future safety policy for fishing vessels in South Korea: adopt international safety benchmarks, focus on occupational and collision accidents, tailor safety measures to vessel size and age, enhance lookout practices to prevent collisions, implement comprehensive strategies to mitigate human errors, and address communication issues among Korean and international crews.

Using lessons learned from a multidecadal intercept survey of Puerto Rico spear fishers to improve data collection in the U.S. Caribbean

AbstractObjectiveSpearfishing is a common activity used to harvest coastal marine species worldwide and can be a significant contributor to landings of ecologically and economically relevant species. As such, it is important to monitor spearfishing catch and effort. Spearfishing is commonly practiced throughout the Caribbean, yet characteristics of this gear's fishery remain understudied in the region. Thus, the objectives of this study were to provide a description of the Puerto Rico spearfishing fishery utilizing a long‐term MRIP APAIS data set, examine the data set quality of this survey, and provide suggestions to improve MRIP implementation in the U.S. Caribbean.MethodsWe described the Puerto Rico recreational spearfishing fishery using a multidecadal (2000–2015) Marine Recreational Information Program (MRIP) Access Point Angler Intercept Survey conducted along the coast of Puerto Rico and surrounding territories. Data issues were identified in the survey results, including possible errors in measurement and identification; therefore, we limited analyses to species composition, enumeration, and mean catch rates.ResultThere were 89 species identified, with snappers (family Lutjanidae) being the most encountered family. Other economically relevant finfish frequently reported were Hogfish Lachnolaimus maximus (n = 121), Queen Triggerfish Balistes vetula (n = 115), and Red Hind Epinephelus guttatus (n = 90). Multiple reef fishes were landed during their spawning season, while prohibited by seasonal closures. Further, spearfishing accounted for 25.8% of the total harvest throughout the study period.ConclusionOur results suggest that spearfishing could be a considerable contributor to finfish landings in Puerto Rico, warranting its continued and improved monitoring in the region. Further, modifications in the design of fisheries surveys are warranted. We suggest increasing the allocation of resources, training, data quality assurance and quality control, and funding for the MRIP to maximize the accuracy of data obtained and meet MRIP U.S. Caribbean priorities. Implementation of a recreational fishing license would assist by creating a registry to monitor total recreational fishing effort and by generating funds to supplement the MRIP. The use of electronic reporting can help mitigate discrepancies with species identification and size measurements and enhance overall recreational fisheries data collection.

Environmental conditions on the Pacific halibut fishing grounds obtained from a decade of coastwide oceanographic monitoring, and the potential application of these data in stock analyses

Context Establishing baseline environmental characteristics of demersal fish habitat is essential to understanding future distribution changes and to identifying shorter-term anomalies that may affect fish density during monitoring efforts. Aims Our aim was to synthesise environmental data to provide near-bottom oceanographic baseline information on the Pacific halibut fishing grounds, to establish geographic groupings that may be used as co-variates in fish-density modelling and to identify temporal trends in the data. Methods Water-column profiler data were collected from 2009 to 2018 along the North American continental shelf, during summer fishery surveys focused on Pacific halibut. Key results In addition to establishing baseline information on the fishing grounds, this analysis illustrated that environmental variables can be grouped geographically into four regions that correspond to the four biological regions established by the International Pacific Halibut Commission. A spatio-temporal modelling approach is presented as an example of how to describe the relationship between environmental data and Pacific halibut distribution. Conclusions This study has highlighted the efficacy of environmental data in analysing fish distribution and density changes. Implications Oceanographic monitoring provides the ability to detect annual anomalies such as seasonal hypoxic zones that may affect fish density and to establish baseline information for future research.

Taking the bait: Environmental factors affecting bait retention and hook disposition in the Gulf of Maine Bottom Longline Survey

Longline fishery surveys are major contributors to groundfish species abundance estimates. Catchability is often assumed constant, but bait is lost or consumed at inconsistent rates during and across gear sets. Accounting for hook availability and gear saturation can improve abundance estimates, but these data are challenging to collect. Our objectives were to determine whether video camera systems can be used to collect these data from the Northeast Fisheries Science Center’s Gulf of Maine Bottom Longline Survey and to explore the associations between hook disposition percentages and environmental characteristics. Electronic monitoring camera systems were deployed on partner vessels during two fall and two spring seasons to capture video of gear retrieval. During post-survey review, individual hooks were recorded as one of the following hook dispositions: bait, empty hook, fish, and invertebrate. Percentages of these hook dispositions were characterized across categorical (season, day or night, and bottom substrata) and continuous (bottom temperature, bottom depth, and substrate rugosity) survey station variables. Nonmetric multidimensional scaling and logistic regression analyses revealed correlations between retained bait and low bottom temperatures, the spring season, shallow depths, rough bottom substrata, and high terrain rugosity. These characteristics were typical of shallow, inshore, and topographically variable survey strata, suggesting that catchability differs among habitat types. This information will be incorporated into catch rate models to develop standardized indices of abundance for groundfish stock assessments. This study is an example of the utility of electronic technologies to supplement on board data collection during cooperative fishery surveys.

Multiple ocean parameter-based potential fishing zone (PFZ) location generation and validation in the Western Bay of Bengal.

A new conceptual framework based on satellite data, including chlorophyll (CHL), sea surface temperature (SST) fronts, relative winds, current vectors, Ekman transport, and eddies, has been developed to identify potential fishing zones (PFZ) in the Bay of Bengal (BoB). The framework aims to provide persistent forecasts, even under cloudy conditions, based on feature propagation. The validation of the PFZ was carried out using fish catch data collected by the Fishery Survey of India (FSI) between 2016 and 2018. Hooking rates (HR) from longlines and catch per unit effort (CPUE) from trawl nets were used to analyse the data points in hook rate categories (1.0-3.0 and > 3.0) and CPUE categories (50-100 kg and > 100 kg) and interpret them with the PFZ maps. The analysis showed that the high fish catch locations were consistent with persisting features in the BoB, such as high chlorophyll patches, SST fronts, and cyclonic eddies. The high fish catch locations based on hook rate and high CPUE were found to be collocated with the high chlorophyll persisting features and thermal gradients in the BoB. The regression analysis shows that availability of the food (CHL) had the strongest correlation with fish catch, followed by the comfort condition (fronts and eddies).

A Numerical Simulation Study and Effectiveness Evaluation on the Flow Field Effect of Trapezoidal Artificial Reefs in Different Layouts

The combined release of artificial reefs in different quantities and arrangements leads to different flow field effects. This study designs a small trapezoidal artificial reef. To optimize the quantity and layout of these reefs, trapezoidal reefs in three different layouts were selected for analysis at five different velocity gradients (0.1, 0.5, 1.0, 1.5, and 2.0 m/s). The effects of disposal spacing and layout on the flow field effect of trapezoidal artificial reefs at different flow velocities were simulated using Ansys Fluent. According to the findings: after simulation, flow velocity could indirectly reflect the distribution of upwelling and back eddy, the scale and strength of upwelling increased as flow velocity increased, and the back eddy showed no obvious variation with flow velocity. In transverse combination mode, both the scale and strength of the upwelling and back eddy were maximized when the reef spacing was 1.0 L; in longitudinal combination mode, upwelling and back eddy reached maximum scale and strength when the disposal spacing of the reefs was 1.5 L of a single reef. In 2020, flow mapping and fishery surveys were carried out in the engineering pilot area. The results showed that the number and species of fish populations with 1.5 L spacing in the vertical combination method were significantly higher than those in other forms, and the structure of the fish reef was stable without any flipping or sliding phenomenon. This study can provide a theoretical reference for the design and the actual deployment of artificial reefs to improve the ecological restoration of the water.

Exploring environmental and biological drivers of cetacean occurrence in the cross-border region of the Malin Shelf using data from a European fishery survey

Irish and Scottish waters are important habitats for cetaceans in Europe. Yet, little data is available for the region of the Malin Shelf, north of Ireland. Despite a rich species diversity, relative cetacean abundance appears low compared to hotspots documented west of Scotland and Ireland. Whether this perceived low prevalence accurately portrays an ecological discontinuity or arises from a lack of published results and low survey effort in that transborder area remains unclear. Here, we used sighting records from a multi-disciplinary fisheries survey, the Western European Shelf Pelagic Acoustic Survey (WESPAS), to explore cetacean habitat preferences over the Malin and Hebridean shelves. Northern minke whale and common dolphin occurrence was modelled within a Bayesian Additive Regression Trees (BART) framework, against selected environmental and biological variables. No correlation was observed between cetacean presence and in-situ prey biomass. Minke whales distribution was better explained by oceanography, notably proxies for frontal activity, and primary productivity. Common dolphins similarly showed preferences for shelf waters within 5-25km of fronts, but also affinities for fine substrates. Favourable habitats identified by the models were consistent with literature around the Hebrides and shed light on potentially important areas along the Islay front and north of Donegal, so far unreported due to data deficiency. Results will contribute towards informing future monitoring, strategic management and conservation efforts in this cross-border region.

Assessing change in the occurrence of rare species using the binomial distribution

The demand for comprehensive biodiversity assessments is increasing through the implementation of the ecosystem-based approach to management (EBM) of marine resources. Regional sea conventions such as the Oslo-Paris Commission (OSPAR) strive to implement EBM by developing an extensive status assessment program for the marine environment. Demersal fish communities are one ecosystem feature assessed by OSPAR through several ecological indicators. One of these indicators assesses the recovery in the population abundance of sensitive fish species, which was initially developed to report on the status of the sensitive fish community as a whole. However, for national reporting obligations, contracting parties of OSPAR (particularly for EU member states reporting to the Marine Strategy Framework Directive) prefer to have assessments for individual species. The previous indicator assessment relied on a suite of demersal fish species, which were caught frequently in scientific groundfish surveys, but did not provide assessment results for rare species caught in low frequencies. This study introduces a new assessment approach, the Binomial Occurrence Assessment (BOA), for the FC-1 indicator now renamed the “Recovery of sensitive fish species”, by applying the binomial distribution to relative occurrence data from scientific fisheries surveys. BOA uses occurrences in a reference period to determine boundaries for the expected occurrences in the recent (six year) assessment period of each survey. Significant changes in occurrence between the reference and assessment period, i.e. declines or recoveries, can then be detected when the observed occurrences in the assessment period fall outside of these boundaries. Methods to integrate the assessment results across multiple surveys are explored and compared since data on occurrences for fish species are available from more than one fisheries survey in each marine region considered by OSPAR. A case study on the sensitive demersal fish species in the North Sea exemplifies the applicability of BOA. Furthermore, assessments by BOA are compared to data from analytical stock assessments for those data-rich sensitive species that can support both approaches. Despite some shortcomings of BOA, such as the inability to detect declines of very rare species and the potential for occurrence metrics to differ from abundance metrics, the BOA allows an assessment of the status of a wide suite of fish species throughout the entire OSPAR region. The low data requirements of BOA allow its generic application to any other monitoring program that has captured occurrences of single species or species suites in the past and present.

Estimation of the value of unreported and unregulated commercial and recreational fisheries at inland waterbodies: case study on the Kama reservoir (Perm krai)

The results of the possible volume of fish harvetsed annually by unreported and unregulated commercial and recreational fisheries at Kama reservoir for the period of 2011–2021 are presented. Two approaches were used to assess the unaccounted commercial catch. The first method is based on the comparison of official commercial catches with scientific research data collected during the surveys of commercial fisheries on the reservoir. The second approach is based on official statistics on the number of fishing gear used by commercial fisheries and the real CPUE values for fished species. The volume of recreational catches is estimated by the number of anglers per unit area of the reservoir, seasonal dynamics of visits to the reservoir by anglers, and the species structure of anglers catch. We found that the volume of possible average annual unaccounted commercial and recreational fish catch may exceed the official data by 2–2,5 times.

Stock status and supporting species of anchovy fisheries in the northern of East Java, Indonesia

Abstract. Wiadnya DGR, Harlyan LI, Rahman MA, Mustikarani SMI, Nadhiroh ENS, Taufani WT. 2023. Stock status and supporting species of anchovy fisheries in the northern of East Java, Indonesia. Biodiversitas 24: 4775-4782. Anchovy, a commercial fish with high demand in local and international markets, was selected as the Unit of Assessment (UoA) of the Fisheries Improvement Project (FIP) based on the priority fisheries consultation process under the Marine Stewardship Council certification in Indonesia. One of the criteria is the availability of stock status and information about supporting species. This research was conducted from January to May 2022 at Lekok Fishing Port, Pasuruan, and Karangagung Fishing Port, Tuban, using primary data collection methods, including a fishery survey to obtain data species composition data and fishing coordinates. The secondary data were the catch-effort data from 2013 to 2021 collected from both fishing ports. Data analysis was carried out by the surplus production models, Schaefer and Fox model, to determine the total allowable catch (TAC) and the exploitation rates of anchovy fisheries. The participatory mapping method was carried out to obtain data on the distribution of fishing grounds and catch composition. The exploitation rate of anchovy (Stolephorus commersonnii) and large anchovy (Encrasicholina punctifer) landed in the Lekok fishing port was 76% and 75% (moderate), respectively. In this situation, fishing efforts can still be increased, as TAC value for anchovy fisheries' sustainability. On the other hand, the exploitation rate of anchovy in the northern waters of Tuban is 105% (over-exploited), which is necessary to reduce fishing efforts for its sustainability. The classification of supporting species resulted in 19 identified species in the Lekok fishing port, covering three target species: two endangered threatened and protected (ETP) species, two main primary species, six minor primary species, one major secondary species, and five minor secondary species. While in Karangagung fishing port, eight species were identified, consisting of 1 major primary species, five minor primary species, and two minor secondary species. The supporting species' information is required to complete FIP Anchovy fisheries.

Length-weight relationship for the dragonfish, Stichopus cf. monotuberculatus (Holothuroidea)

Length-weight relationships are commonly used to convert length measurements to body weights for data from population surveys, to generate estimates of biomass for stock assessment. These morphometric relationships assess whether increases in body weight are proportional to unit increases in length, providing an insight into growth. Few biological data are available for the nocturnally active sea cucumber, Stichopus cf. monotuberculatus, which is harvested throughout the Indo-Pacific region. This study assessed the morphometric relationships between body length and weight, and basal area and weight for three broad colour variants of S. cf. monotuberculatus at two reefs on the Southern Great Barrier Reef. Preparation of ossicles from the external tissues of the animals validated the species identification. All morphometric relationships were significant and revealed negative allometric growth (exponent, b, range = 2.17–2.42), as found in other holothuroids. Despite some deviance in length-weight relationships between colour types, the largely overlapping data points suggest that a single equation should be appropriate for weight estimation of S. cf. monotuberculatus. Length measurements alone were sufficient for estimating weight (r2 = 0.80) because the addition of width measurements made no tangible improvement to the model fit. The findings indicate that this sea cucumber maintains a relatively consistent shape, with limited contraction of the body. These results will be useful for estimations of weight in future fishery surveys to estimate stock biomass and catch volumes.

Modelling andin situobservation of broadband acoustic scattering from the Silver cyprinid (Rastrineobola argentea)in Lake Victoria, East Africa

AbstractLake Victoria is the second-largest freshwater lake in the world, and fish from the lake are a vital food resource for millions of people living around it. The silver cyprinid (Rastrineobola argentea), a small schooling pelagic species known in Tanzania as “dagaa” contributes ca. 55% to the total annual catch (ca. 0.51 million tonnes (MT) in 2014). The acoustic target strength (TS, dB re 1 m2) of dagaa, a key factor for biomass estimation, is however not well described, and is a major source of uncertainty in biomass estimation. In this study, we developed a Kirchhoff-ray mode (KRM) model to predict the TS of dagaa at standard fisheries survey frequencies. The model was based on the morphology of the body and the dual-chambered swimbladder, as obtained from X-ray images of fish ranging in total length (TL) between 2.8 and 5.4 cm. The results suggested that the swimbladder (which comprises 2.6 to 8.2% of body volume) accounts for ca. 65 to 90% of the total backscattering at 120 kHz. The predicted TS was highly dependent on tilt angle, varying by 14.0 dB at 120 kHz across the tilt range 65–115˚ (where 0˚ is head up and 180˚ is tail up), and TS variability with tilt generally increased with increasing frequency. The tilt angle of acoustically tracked individual fish indicated a distribution of tilt angles with a mean and s.d. of 93.5 and 15.1°. Our model suggested a new tilt-averaged TS–TL relationship for dagaa [$T{S}_{120\ kHz} = 19.49\log ( {TL} ) - 70.3$], which leads to a TS 1.5 dB higher than the value in the relationship presently used to estimate stock biomass. The new relationship will lead to a substantial reduction (by ca. 30%) in estimated biomass. The discrepancies between the mean relative frequency response of the in situ measurements of backscatter from dagaa and the KRM model predictions were in the range of -2.9–3.1 dB at frequencies from 45 to 250 kHz. The KRM modelling and in situ broadband measurements of dagaa will be beneficial for acoustic identification and behavioural studies of dagaa, and will enable improved biomass assessment, thereby underpinning sustainable long-term management.

Estimating lentic recreational fisheries catch and effort across the United States

AbstractRecreational fisheries represent a socially, ecologically, and economically significant component of global fisheries. The U.S. Inland Creel and Angler Survey Catalog (CreelCat) database includes inland recreational fisheries survey data across the United States to facilitate large‐scale analyses. However, because survey methods differ, a statistical method capable of integrating these surveys is necessary to assess patterns and relationships across regions. Here, we developed a hierarchical generalized linear mixed modeling approach to estimate the relationship between daily recreational fisheries catch and effort based on waterbody, socio‐economic, and ecological covariates. We applied this approach to CreelCat data on lentic waterbodies and found that recreational fisheries catch and effort were non‐linearly related (i.e., catch per unit of effort declined as effort increased), where effort varied regionally and by waterbody area, median county age, and distance to nearest primary road. This modeling approach could be used to inform data‐poor regions or waterbodies, make comparisons across spatial scales, and, with the inclusion of socio‐economic and ecological factors, inform management techniques in an era of shifting demographics and landscapes.

Estimates of adult Lake Trout mortality fromcoded wiretags in a population with developing natural reproduction in southern Lake Michigan

AbstractObjectiveOverfishing and Sea LampreyPetromyzon marinuspredation led to extirpation of Lake TroutSalvelinus namaycushfrom Lake Michigan in the 1950s. Large populations of hatchery‐reared fish were developed by the 1970s, but natural reproduction was limited until the early 2000s when it began to increase in the southern main basin. Hypothesizing that the relatively low mortality of spawning‐aged fish contributed to this reproductive success, we estimated the total annual mortality rate for this population.MethodsWe used catch curves to estimate the total instantaneous mortality rateZusing coded wire tags, which provided definitive ages. We made separate estimates from fish collected in three on‐going surveys: a spring gill‐net survey, a fall gill‐net spawning survey, and a sport fishery survey.ResultOur estimates ofZ ± SE were 0.297 ± 0.019, 0.239 ± 0.009, and 0.205 ± 0.007 for the spring, spawning, and sport fishery surveys, respectively. We suggest that the meanZ ± SE of all survey estimates of 0.247 ± 0.027 would be a reasonable estimate for this population, which equates to a total annual mortality of 22 ± 3%. This estimate is in the low range of rates reported for the species and is in the same range as other populations in the Great Lakes with well‐established natural reproduction.ConclusionWe concluded that these low total mortality rates contributed to the reproductive success in southern Lake Michigan through increasing spawning stock density and age structure and that previous estimates of another important population parameter, the instantaneous natural mortality rateM, were too high. Estimates ofMranged from 0.210 to 0.240 and were based on the Pauly equation, a growth‐ and temperature‐based estimator. We suggest maximum‐age‐based estimators ofMare more appropriate for Lake Trout. Several alternative maximum‐age‐based estimators produced estimates forMof 0.132–0.058, all of which are more compatible with our estimate ofZ.