Future Fisheries Management Research Articles

High Prevalence of the Copepod Salmincola californiensis in Steelhead Trout in Lake Ontario Following its Recent Invasion

Salmincola californiensis (Dana, 1853) (Subclass Copepoda: Family Lernaeopodidae) is known to parasitize salmonids of the genus Oncorhynchus including Oncorhynchus mykiss (rainbow trout), Oncorhynchus tshawytscha (chinook salmon), and Oncorhynchus kisutch (coho salmon). These 3 salmonids have been introduced to the Great Lakes intermittently since the mid-1800s. As we demonstrate here, the introduction of these salmonids to the Great Lakes was followed, at some point, by the introduction of their parasitic gill copepod, S. californiensis. Given anecdotal accounts of S. californiensis in introduced salmonids in Lake Ontario since 2012, we chose to conduct a survey to formally document the occurrence of this introduced species. Our survey took place during spring, summer, and fall of 2018 and during spring of 2019 at the south-eastern side of Lake Ontario. Prevalence of S. californiensis was 69, with a mean intensity of 2.7 in 61 rainbow trout examined in 2018. In 2019, prevalence of S. californiensis was 71, with a mean intensity of 3.6 in 59 rainbow trout examined. The prevalence of S. californiensis was 39, with a mean intensity of 1.6 in 223 chinook salmon examined in 2018. No specimens of S. californiensis were found in the 100 coho salmon examined in 2018. The prevalence of S. californiensis in rainbow trout is of great concern considering that it is double that found in rainbow trout in the native range (69 [in 2018] and 71 [in 2019] vs. 35). This is the first formal documentation of the invasion of S. californiensis in Lake Ontario. Future fisheries management decisions in Lake Ontario and its tributaries should take into account these data.

Incorporating environmental forcing in developing ecosystem-based fisheries management strategies

AbstractThis study incorporated two pathways of environmental forcing (i.e. “larval mortality forcing” and “somatic growth forcing”) into an end-to-end ecosystem model (Object-oriented Simulator of Marine ecOSystEms, OSMOSE) developed for the Pacific North Coast Integrated Management Area (PNCIMA) off western Canada, in order to evaluate alternative fisheries management strategies under environmental changes. With a suite of ecosystem-level indicators, the present study first compared the ecosystem effects of different pathways of environmental forcing scenarios; and then evaluated the alternative fisheries management strategies which encompassed a series of fishing mortality rates relative to FMSY (the fishing mortality rate that produces maximum sustainable yield) and a set of precautionary harvest control rules (HCRs). The main objectives of this study were to (i) explore the ecosystem effects of different environmental forcing scenarios; (ii) identify the impacts of different fishing mortality rates on marine ecosystem structure and function; and (iii) evaluate the ecosystem-level performance of various levels of precautionary HCRs. Results indicated that different pathways of environmental forcing had different ecosystem effects and incorporating appropriate HCRs in the fisheries management process could help maintain ecosystem health and sustainable fisheries. This study provides important information on future fisheries management options within similar marine ecosystems that are facing global changes.

The characteristics of krill swarms in relation to aggregating Antarctic blue whales

We model the presence of rare Antarctic blue whales (Balaenoptera musculus intermedia) in relation to the swarm characteristics of their main prey species, Antarctic krill (Euphausia superba). A combination of visual observations and recent advances in passive acoustic technology were used to locate Antarctic blue whales, whilst simultaneously using active underwater acoustics to characterise the distribution, size, depth, composition and density of krill swarms. Krill swarm characteristics and blue whale presence were examined at a range of spatiotemporal scales to investigate sub meso-scale (i.e., <100 km) foraging behaviour. Results suggest that at all scales, Antarctic blue whales are more likely to be detected within the vicinity of krill swarms with a higher density of krill, those found shallower in the water column, and those of greater vertical height. These findings support hypotheses that as lunge-feeders of extreme size, Antarctic blue whales target shallow, dense krill swarms to maximise their energy intake. As both Antarctic krill and blue whales play a key role in the Southern Ocean ecosystem, the nature of their predator-prey dynamics is an important consideration, not only for the recovery of this endangered species in a changing environment, but for the future management of Antarctic krill fisheries.

Modeling the distribution of thorny skate (Amblyraja radiata) in the southern Grand Banks (Newfoundland, Canada)

Globally, commercial fisheries have had a strong impact on elasmobranch populations directly through high catch rates and indirectly through bycatch. Consequently, the abundance of many species is declining to the extent that some are considered under threat of extinction. Regionally, this negative trend is also evident in the international waters of the southern Grand Banks (off the coast of Newfoundland, Canada), where the occurrence of the thorny skate (Amblyraja radiata) has declined by nearly 70% in recent decades. This study used Bayesian species distribution models to investigate the habitat preference and biomass trends of the thorny skate during a 14-year period (2003–2017), linking five environmental predictors (i.e., bathymetry, sea bottom temperature, seabed aspect, slope, and rugosity) and prey distribution with fishery-independent data. Our findings identify some of the sensitive habitats for this species and the ecological factors that may be driving its population dynamics in the area. We argue that knowledge about the factors influencing the distribution of this species and spatiotemporal effects could be exploited as potential mitigation measures for future fishery management strategies.

Exploring the agentic power in fishery: reflections from fishing communities of Lake Tanganyika, Kigoma, Tanzania

One of the central concerns of fisheries management is to understand the dynamics in the human-environment interactions especially in the context of the observed declining fish resources. This paper examines how agentic power drives the human-environment interactions. Drawing on interviews with fishers from Lake Tanganyika in Kigoma, Tanzania, the paper demonstrates how fishers negotiate their ways out of the structured rules and regulations to be able to access and benefit from the Lake’s fish resources. Actors in the study areas maneuvered their way through the externally driven and established rules and regulations set to manage the fisheries. Thus, instead of actors being passive recipients of these external rules and regulations, they actively engage with them and challenge those that affect or contradict with community values and norms, which enable access to fish resources. It is therefore argued that actors are capable of negotiating their ways to access fish resources, even in the face of institutional structures that would otherwise impede these efforts. Their power to invent new possibilities to respond to problematic situations needs to be acknowledged by resource managers as they seek alternative approaches to future fishery management strategies.

Forage fish to growing chicks: shared food resources between two closely related tern species

The assessment of the relevance of forage fish in seabird diet and how different species partition food resources is fundamental to understand predator–prey relationships. We assessed the importance of forage fish in the diet of Royal (Thalasseus maximus maximus) and Cayenne (T. sandvicensis eurygnathus) terns and their partitioning of food resources during the early and late chick stages of 2013 and 2014 at a colony in Argentina. Direct observation of prey deliveries during chick provisioning showed that diet composition of Royal and Cayenne terns comprised at least 16 and 9 prey species, respectively. In both tern species, Argentine Anchovy (Engraulis anchoita) and five species of silversides (Odontesthes spp.) were the main prey fed to chicks (over 90% contribution, anchovy and silversides pooled). Both tern species fed their chicks with similar prey species, but Royal terns delivered, in general, larger prey than Cayenne terns. Based on carbon and nitrogen isotopic values from chick whole blood samples, Bayesian mixing models showed that anchovies and silversides contributed similarly to the diet of both tern species’ chicks. Both conventional and stable isotope methods showed a high overlap in their trophic niches. Prey sizes delivered to chicks were larger in the late chick stage and the second study season. Wind speed did not have a significant effect on the frequency of the different prey species and sizes delivered to chicks by both tern species. As anchovies and silversides are fishery targets, tern trophic requirements should be considered when planning future fisheries development and management.

“Bring fishermen at the center”: the value of local knowledge for understanding fisheries resources and climate-related changes in Lake Tanganyika

In this paper, we discuss the value of local knowledge of fishermen from Kigoma, along the North Eastern shores of Lake Tanganyika, regarding fish and climate-related issues of the lake. We explore how that knowledge can be incorporated into sustainable management activities. We used a qualitative approach to investigate the local knowledge and perception of changes and their causes. About 64 respondents comprising fishermen, fish processers, Beach Management Unit leaders, fisheries officers and elders were interviewed between April and December 2016. Our analysis shows that there have been increasing fishing activities in the lake from the 1970s. Increased fishing activities and climate-related changes in the lake have resulted in dramatic decreases in fish landings between the 1990s and the present. It was also revealed that fishermen hold valuable knowledge on fish availability, ecological conditions of the lake, and seasonal weather conditions. While they acknowledge the effects of changes in fishing practices and fishing pressure to explain the gradually decreasing fisheries, they have less understanding of the importance of longer-term changes in the lake environment resulting from climate change. This study concludes that future fisheries management could benefit from further incorporation of fishers’ local knowledge such as those related to ecological conditions of the lake and pressures from fishing practices. By expanding mechanisms to include the fishermen’s local knowledge, a strong signal is sent to them that their knowledge is valued by fisheries management. This has the potential to further motivate the fishermen to be active participants in contributing to sustainable management practices that can positively impact declining fish resources. In other words, fishermen need to be further “brought at the center” in decision-making processes that influence fisheries management options.

‘Real interest’? Understanding the 2018 Agreement to Prevent Unregulated High Seas Fisheries in the Central Arctic Ocean

AbstractThe 2018 Agreement to Prevent Unregulated High Seas Fisheries in the Central Arctic Ocean (Agreement) is a notable intervention in living resources management. The Agreement seeks to anticipate future fisheries management and serves as a reminder as how international legal frameworks such as UNCLOS ‘regionalise’ seas and oceans. But thus far analyses of the Agreement have tended to focus on its legal and managerial qualities and implications. This paper offers a different reading of the Agreement, informed by critical geopolitics, which focuses on how the Agreement actively produces ‘the Central Arctic Ocean’ (CAO) which it then seeks to manage. The Agreement will shape not only the future geopolitics of the Arctic Ocean but also the diverse array of interests held by Arctic Ocean coastal states, indigenous peoples, environmental groups and extra‐territorial parties such as China.

Potential of Sustainable Fishery Resources at Giam Siak Kecil-Bukit Batu Biosphere Reserve, Riau Province, Indonesia

Fisheries are fundamental part of human activities. Sustainable fishing is an important aspect in maintining the fishery resources for the future generation. The main objective of this study is to estimate the maximum sustainable yield (MSY) of the fishing grounds for the sustainable harvesting. This study deploy the approximate estimation of abundance (biomass) and potential estimation of a type or group of fish species based on the analysis of production surplus to determine the sustainability of maximum catch rate. Results of the research identified about 35 species from the 17 families of fish. Based on the MSY calculation using the Schaefer method with a long line standard, the fish utilization status is in overfishing condition status at all sampling points, with the value above 98% above the standard capture limit of 70%. The results of the Schaefer model provide the baseline information on MYS for the freshwaters fish, which could be used as the basis for future fishery assessment and management of this biosphere reserve.

Using species distribution model to predict the impact of climate change on the potential distribution of Japanese whiting Sillago japonica

Climate change is one of the most serious global environmental problems and it is of great importance to understand how species respond to climate change. Species distribution models (SDMs) have been regarded as an effective tool to examine the impacts of climate change on species’ potential distribution. In this study, we developed a SDM for a marine fish, the Japanese whiting Sillago japonica by using records of its occurrence and five predictor variables (ocean depth, distance to shore, mean sea surface temperature, salinity, and currents velocity) and predicted its habitat suitability for current conditions and under scenarios of future climates. The SDM suggests that ocean depth, distance to shore, and temperature are the three most important predictor variables determining the distribution of S. japonica. Our SDM accurately predicted the current distribution of the species, with values of true skill statistics and area under the receiver operating characteristic curve above 0.95. Under future climate scenarios, the suitable habitat of S. japonica is predicted to become smaller in size and to shift northward. Differences between climate change scenarios for 2040–2050 and 2090–2100 showed that this species will lose more suitable habitat as climate change progresses over time. Future fisheries management strategies should take this range contraction and associated northward shift into account.

Sudden change in long‐term ocean climate fluctuations corresponds with ecosystem alterations and reduced recruitment in Norwegian spring‐spawning herring (Clupea harengus, Clupeidae)

AbstractFish stocks vary in abundance. The causes behind the fluctuations may be difficult to determine, especially ones caused by natural fluctuations, but long‐term data series may provide indications of the mechanisms. Assessments show that the recruitment to the Norwegian spring‐spawning herring (Clupea harengus, Clupeidae) has remained low since 2004, a year which produced the last really rich year‐class. Long time‐series of estimated recruitment and mean winter temperature in the ocean showed a significant positive correlation for the period 1921–2004. Here, we show that this positive correlation did not continue from 2005 onwards as the winter temperature increased to high levels while herring recruitment decreased and has remained low. The density of zooplankton in the drift route of the herring larvae dropped significantly after 2004, and their centre of gravity shifted northwards. There may currently be heavy predation on the larvae by Atlanic mackerel (Scomber scombrus, Scombridae), and top‐down regulation is suggested to hamper successful recruitment. Our analysis indicates that the presence of food and overlap with high food concentrations are likely important regulators of survival in herring larvae. The findings may be important for future management and planning of fisheries of this stock because recruitment failure may continue if temperature remains high and food abundance remains low.

Effects of a rainbow trout stocking moratorium on the Daphnia species composition and water quality of Square Lake (Minnesota)

Hembre, LK. 2019. Effects of a rainbow trout stocking moratorium on the Daphnia species composition and water quality of Square Lake (Minnesota). Lake Reserv Manage. 35:127–139.Square Lake is among the clearest lakes in the Minneapolis–St. Paul (Minnesota) metropolitan area, but its water clarity has decreased over the past several decades despite levels of total phosphorus (TP) remaining relatively stable. Predation by zooplanktivorous rainbow trout annually stocked since the early 1980s was hypothesized to be the cause for this eutrophication trend. To evaluate this hypothesis, a 3-year moratorium on trout stocking was imposed by the Minnesota Department of Natural Resources (MNDNR) and water quality and zooplankton monitoring data from 2 years prior to the moratorium (2010 and 2012) were compared to data from the 3 moratorium years (2013–2015). Significant changes observed during the moratorium years that support the hypothesis include (1) an increase in biomass concentrations of the large-bodied Daphnia pulicaria, (2) a coincident decrease in biomass concentrations of the smaller bodied D. mendotae, and (3) more pronounced spring clear-water phases when D. pulicaria reached peak densities. In addition, the volume of hypoxic water (dissolved oxygen [DO] < 1 mg/L) that developed in deep water was less in moratorium years compared to the premoratorium years. Unexpectedly, surface water TP concentrations were significantly lower during the moratorium years than in premoratorium years. Greater sequestration of P in the biomass of Daphnia during the moratorium years is the likely cause for the decrease in surface water TP levels in those years. Natural resource managers from the MNDNR have extended the moratorium and are using the conclusions from this study to determine the future fisheries management plan for Square Lake.

FISHERY PARAMETERS AND POPULATION DYNAMICS OF SILVER CROAKER ON THE XINGU RIVER, BRAZILIAN AMAZON

The study analyzed the fishery parameters and population dynamics of the silver croaker, Plagioscion squamosissimus, and its exploitation status, before the damming of the Xingu River by the Belo Monte hydroelectric dam. Silver croaker was caught throughout the year, with a total production of 239 tons. Estimated Catch per Unit Effort (CPUE) was 14.16 kg.fisher-1.day-1. The mean price paid to the fishers for a kilogram of silver croaker ranged from US$1.89 to US$3.28. Mean longevity estimated was 7.68 years. The total mortality (Z) was calculated at approximately 1.44 year-1, natural mortality (M) was 0.76 year-1, fishery mortality (F) was 0.68 year-1, and the current exploitation rate (E) was 0.47 year-1. The study highlights the importance of P. squamosissimus as a fishery resource in the Xingu region and provides important insights for the development of future fishery management strategies and conservation of the species stocks.

Boom‐bust like dynamics of invasive black bullhead (Ameiurus melas) in Lake Sava (Serbia)

AbstractThe life‐history traits and population dynamics of the black bullhead Ameiurus melas (Rafinesque) were studied monthly from August 2009 to December 2012 in Lake Sava in Belgrade (Serbia). This period included a mass mortality event in May 2011 and subsequent population recovery during 2012. Available evidence suggests the mass mortality was caused by European catfish virus that only affected the black bullhead. Changes in key life‐history traits and the recovery potential (increase in catch‐per‐unit‐effort, doubling of young‐of‐the‐year to adult ratio, earlier maturation and increased fecundity) following the mass mortality event suggest population resilience typical of a recurring boom‐bust pattern and demonstrate the species’ capacity to recover rapidly and re‐establish following disturbance. Repeated systematic mass removals of both juveniles and adults (using fyke nets) will be required if future fishery management measures aimed at limiting the population size are to be effective.

Evaluation of an unreported and unregulated sea cucumber fishery in eastern Brazil

Holothuria grisea is abundant in Brazil, however there is only one study on this species. This study aimed to characterize the sea cucumber fishery in the State of Ceará, Brazil, through the evaluation of the capture, length classes most susceptible to catch, fishing effort as well as the processing, stakeholders characterization, income and marketing of the final product. The study was carried out in two fishing communities (Xavier and Camocim) from August 2015 to July 2016. Processing is performed in four stages: evisceration, cooking, draining and drying. The fishing cycle occurs in spring tides. The annual catch was 12,341 kg, which was totally commercialized. The t-test shows that there was no significant difference for capture per unit effort (CPUE) and fishing effort between communities. The processed individuals showed an average loss of 79% weight and 49% length. 66% of the captured organisms were below the size at first maturity. This activity plays an important role as complementary income. However, this is an unreported and unregulated activity and an intense fishing pressure can lead to overexploitation of this resource. This study is essential to not only the knowledge of the dynamics of this activity, but also as an attempt to contribute to a future fishery management.

Does Climate Change Bolster the Case for Fishery Reform in Asia?

I examine the estimated economic, ecological, and food security effects of future fishery management reform in Asia. Without climate change, most Asian fisheries stand to gain substantially from reforms. Optimizing fishery management could increase catch by 24% and profit by 34% over business-as-usual management. These benefits arise from fishing some stocks more conservatively and others more aggressively. Although climate change is expected to reduce carrying capacity in 55% of Asian fisheries, I find that under climate change large benefits from fishery management reform are maintained, though these benefits are heterogeneous. The case for reform remains strong for both catch and profit, though these numbers are slightly lower than in the no-climate change case. These results suggest that, to maximize economic output and food security, Asian fisheries will benefit substantially from the transition to catch shares or other economically rational fishery management institutions, despite the looming effects of climate change.

Morphology of the first zoea of Chaceon affinis (A. Milne-Edwards Bouvier, 1894) and occurrence of Chaceon spp. larvae (Decapoda: Brachyura: Gerynonidae) in the Canary Islands waters, Northeastern Atlantic.

The morphology of the first zoea stage of Chaceon affinis is described and illustrated in detail for the first time. Morphological comparison with the corresponding stage of other known species of Geryonidae allowed the differentiation between the genera Chaceon and Geryon, although it was impossible to distinguish among species of Chaceon using larval morphology. Thus, geryonid larvae collected in the plankton of Gran Canaria Island, NE Atlantic, during the years 2005 and 2006, could only be identified as Chaceon spp. The temporal distribution of larval abundance suggested that main hatching periods of Chaceon spp. occur in spring and summer. These results are useful to better understand the reproductive strategies of these deep-water crabs, which in turn will be useful for future fishery management of this resource of increasing interest in the Canary Islands.

“Nature’s Little Helpers”: A benefits approach to voluntary cultivation of hatchery fish to support wild Atlantic salmon (Salmo salar) populations in Norway, Wales, and Germany

Voluntary hatcheries, or hatcheries operated privately by local anglers and fishery owners, are a historical part of salmonid conservation and enhancement efforts in Europe. However, these types of hatcheries have faced increasing scrutiny over the last several decades because of the potential negative ecological impacts created by stocking salmon into wild (albeit declining) populations. We hypothesized that hatchery programs provide value to communities well beyond the possible conservation contribution to local salmon. Utilizing a qualitative ethnographic approach, we identified and classified a range of benefits produced by voluntary salmon hatcheries within three case studies in Norway, Wales, and Germany. Across all cases, voluntary hatcheries facilitated or provided diverse social, psychological, and conservation benefits to individuals and groups of cultivators, as well as to the river environment. Voluntary hatcheries can be considered as a visible means of environmental stewardship and are perceived by many operators as an important means for mitigating human obstacles to wild salmon conservation. Based on the multiple benefits that voluntary hatcheries create for the people engaged in hatchery activities, we lay out alternative views that add to the traditionally black-and-white, pro or anti-hatchery perspectives. Improved incorporation of multiple social-psychological hatchery benefits into future fisheries management decisions, outreach, and communication will provide a more holistic approach to sustainable hatchery management, reduce stakeholder conflict, foster civil engagement in salmon conservation, and enhance environmental stewardship.

Gonad development and spawning of the Vulnerable commercial sea cucumber, Stichopus herrmanni, in the southern Great Barrier Reef

Despite the important ecological roles of commercial bêche-de-mer holothuroids in coral reef ecosystems their reproductive biology is poorly studied, including on the Great Barrier Reef (GBR). We investigated reproduction of Stichopus herrmanni, a commercially important species listed as Vulnerable, at One Tree Island, southern GBR. Gonad index, histology and spawning observations indicated an annual reproductive cycle with gamete release in the Austral spring and summer (November–February), as for populations of this species at a similar latitude in New Caledonia. Stichopus herrmanni releases gametes episodically, spawning multiple times during summer. Assimilation of spawning observations from OTI and elsewhere along the GBR and tropical Pacific revealed that gamete release by S. herrmanni is influenced by the lunar cycle, with spawning taking place around the new moon in summer. This species is an aggregative spawner with a behavioural change to attain elevated positions on the reef at dusk prior to spawning. After the spawning season, gametes remaining in the gonads are reabsorbed. Spent gonads completely lacked gametes. There was a quiescence in gonad development in winter with an absence of gonads in some specimens, indicating an aestivation-like period for reproduction. By late-winter (August) recovery stage gonads were distinguished by the initiation of gametogenesis, which coincided with increasing temperature and day length. Our findings contribute to the understanding of the reproductive biology of S. herrmanni, a consideration for future fisheries management in the protection of this Vulnerable species, especially with respect to the increasing global trade in bêche-de-mer.

Modeling the Dispersal of Spiny Lobster (Palinurus elephas) Larvae: Implications for Future Fisheries Management and Conservation Measures

Knowledge of larval dispersal, population dynamics and connectivity in relation to the management and conservation of commercially important species is vital if existing fisheries are to remain sustainable into the future. Larval dispersal of the commercially exploited spiny lobster, Palinurus elephas, was modelled from Marine Protected Areas located in the southwest of England for a 16-month period using a General Individuals Transport Model (GITM). The model included physical particle advection based on current fields from a 3D hydrodynamics model and a larval behaviour module. Our results demonstrate the overall dispersal patterns of P. elephas larvae and highlight populations capable of self-seeding and those which are seemingly reliant on larvae from more distant populations. The results indicate where further research may be required to fully understand how populations of P. elephas are maintained at regional, national and international scales while providing us with the opportunity to discuss the effectiveness of current approaches to conservation and fisheries management.