Fisheries and Fisheries Management

First Large-Scale Eastern Mediterranean and Black Sea Stock Assessment Reveals a Dramatic Decline

Demirel N, Zengin M, Ulman A. First Large-Scale Eastern Mediterranean and Black Sea Stock Assessment Reveals a Dramatic Decline. Frontiers in Marine Science [Internet]. 2020 ;7. Available from: https://www.frontiersin.org/article/10.3389/fmars.2020.00103/full
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

The Mediterranean Sea is classified as a “data-poor” region in fisheries due to its low number of assessed stocks given its biodiversity and number of exploited species. In this study, the CMSY method was applied to assess the status and exploitation levels of 54 commercial fish and invertebrate stocks belonging to 34 species fished by Turkish fleets in the Eastern Mediterranean (Levantine) and Black Seas, by using catch data and resilience indices. Most of these marine taxa currently lack formal stock assessments. The CMSY method uses a surplus production model (SPM), based on official catch statistics and an abundance index derived from scientific surveys. The SPM estimates maximum sustainable yield (MSY), fishing mortality (F), biomass (B), fishing mortality to achieve sustainable catches (Fmsy), and the biomass to support sustainable catches (Bmsy). Our results show the estimated biomass values for 94% of the stocks were lower than the required amount to support sustainable fisheries (Bmsy). Of the 54 stocks, 85% of them can be deemed as overfished; two stocks were not subject to overfishing (Sardina pilchardus and Trachurus mediterraneus in the Marmara Sea) while only one stock (Sprattus sprattus in the Black Sea) is healthy and capable of producing MSY. Annual values of the stock status indicators, F/Fmsy and B/Bmsy, had opposing trends in all regions, suggesting higher stock biomasses could only be achieved if fishing mortality is drastically reduced. Recovery times and levels were then explored under four varying F/Fmsy scenarios. Under the best-case scenario (i.e., F = 0.5Fmsy), over 60% of the stocks could be rebuilt by 2032. By contrast, if normal fishing practices continue as usual, all stocks will soon be depleted [if not already] (F = 0.95Fmsy), whose recover may be impossible at later dates. The results of this study are supported by previous regional assessments confirming the overexploitation of Turkish fisheries is driving the near-total collapse of these marine wild fisheries. Hence, the need to urgently rebuild Turkey’s marine fisheries ought to be prioritized to ensure their future viability.

Vulnerability of Demersal Fish Assemblages to Trawling Activities: A Traits-Based Index

de Juan S, Hinz H, Sartor P, Vitale S, Bentes L, Bellido JM, Musumeci C, Massi D, Gancitano V, Demestre M. Vulnerability of Demersal Fish Assemblages to Trawling Activities: A Traits-Based Index. Frontiers in Marine Science [Internet]. 2020 ;7. Available from: https://www.frontiersin.org/article/10.3389/fmars.2020.00044/full
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Reducing the impact on vulnerable species through changes in fishing practices, such as the spatial or temporal avoidance of certain areas, is key to increase the ecological sustainability of fisheries. However, it is often hampered by the availability of sufficiently detailed data and robust indicators. Existing trawl surveys are a cost-effective data source to assess the vulnerability of fishing areas based on the quantities of vulnerable species caught. We developed a biological traits-based approach to the vulnerability of demersal assemblages using commercial trawl catch data. An expert-based approach identified a set of biological traits that are expected to condition the species’ response to trawling impact and are combined to produce the vulnerability index ranked into four levels (low, moderate, high, and very high vulnerability). The approach was tested in four southern European fishing grounds showing evidence of over-exploitation, through catches being dominated by species of relatively low vulnerability to fishing impacts. The general distribution of species’ biomass amongst vulnerability groups was highly homogenous across case studies, despite local differences in fishing fleet structure, target species and fishing depths. Within all areas the species with moderate vulnerability dominated and, in most instances, species of “very high” vulnerability were not recorded. Nevertheless, differences emerged when comparing the proportions of highly vulnerable species in the catches. Variability in vulnerability level of the catch was also observed at small spatial scales, which was principally explained by differences in habitat type and depth and, secondarily, by fishing effort. In fine mud in the shallower areas there was a higher presence of low vulnerable fauna. Furthermore, vulnerable organisms decreased in their presence in sandier substrates on the continental shelf. The spatial heterogeneity in assemblage vulnerability composition encourages the potential for adoption of this index in the spatial management of fishing grounds aiming at ensuring a sustainable exploitation by mitigating trawl impacts on the most vulnerable components of the demersal assemblages.

A Review of Cumulative Effects Research and Assessment in Fisheries and Oceans Canada

Murray C, Hannah L, Locke A. A Review of Cumulative Effects Research and Assessment in Fisheries and Oceans Canada. Fisheries and Oceans Canada; 2020.
Freely available?: 
Yes
Summary available?: 
No
Type: Report

The study and management of cumulative effects is an emerging field and an area of critical importance to Fisheries and Oceans Canada (DFO). Cumulative effects are defined as “...changes to the environment that are caused by an action in combination with other past, present and future human actions” (Hegmann et al. 1999) and, crucially, can result from individually minor but collectively significant actions taking place over a period of time or across an area. The need for assessment of cumulative effects is evident throughout the programs and objectives of DFO, and is required to support management decisions by multiple DFO sectors. An overarching cumulative effects strategy for DFO, would provide a consistent approach and guidance for the assessment of cumulative effects through development of standard methods that build on existing general theoretical frameworks and applications. This report collates and reviews previous and ongoing existing cumulative effects research and assessments conducted by DFO, focusing on marine ecosystems. Based on the range of existing work and needs within DFO programs, we outline a strategy for assessing cumulative effects that uses a typology of cumulative effect assessment frameworks consisting of four types: activity-based, stressor-based, species- or habitat-based, and area-based.

Total Allowable Catch of Indonesian Southern Bluefin Tuna Thunnus maccoyii and Its Potential Resources in The Indian Ocean

Rochman F, Agustina M, Arnenda GLevi. Total Allowable Catch of Indonesian Southern Bluefin Tuna Thunnus maccoyii and Its Potential Resources in The Indian Ocean. E3S Web of Conferences [Internet]. 2020 ;147:02013. Available from: https://www.e3s-conferences.org/articles/e3sconf/abs/2020/07/e3sconf_ismfr20_02013/e3sconf_ismfr20_02013.html
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Southern Bluefin Tuna (SBT) is a high value species fished by many countries including Indonesia, and its fishing activities has been regulated by CCSBT. This study aimed to determine the potential resource of Indonesian SBT, utilization, and review of the Total Allowable Catch (TAC) of Indonesian SBT. This research was conducted from January 2017 to April 2018. The primary data used in this study were the otolith samples and the enumeration data of SBT landed in Benoa port from 2012-2017. Virtual Population Analysis (VPA) used in this research was based on a direct aging method using otolith. This research showed that the catch at age structure was distributed from 5-22 years with mean and mode of age were 9.63 and 9 years. The average of the exploitation rate measured was 0.191 per year meaning that the level of exploitation was categorized as underfished. The optimal assumption of the exploitation rate estimated in the range of 1,577 to 2,630 tons per year which is higher than the TAC provided by CCSBT. It was concluded that from 2015 onwards, the catch efforts were more effective and efficient with the increasing level of the exploitation and the decreasing number of efforts.

Long-term observations from Antarctica demonstrate that mismatched scales of fisheries management and predator-prey interaction lead to erroneous conclusions about precaution

Watters GM, Hinke JT, Reiss CS. Long-term observations from Antarctica demonstrate that mismatched scales of fisheries management and predator-prey interaction lead to erroneous conclusions about precaution. Scientific Reports [Internet]. 2020 ;10(1). Available from: https://www.nature.com/articles/s41598-020-59223-9#article-info
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Low catch limits for forage species are often considered to be precautionary measures that can help conserve marine predators. Difficulties measuring the impacts of fisheries removals on dependent predators maintain this perspective, but consideration of the spatio-temporal scales over which forage species, their predators, and fisheries interact can aid assessment of whether low catch limits are as precautionary as presumed. Antarctic krill are targeted by the largest fishery in the Southern Ocean and are key forage for numerous predators. Current krill removals are considered precautionary and have not been previously observed to affect krill-dependent predators, like penguins. Using a hierarchical model and 30+ years of monitoring data, we show that expected penguin performance was reduced when local harvest rates of krill were ≥0.1, and this effect was similar in magnitude to that of poor environmental conditions. With continued climate warming and high local harvest rates, future observations of penguin performance are predicted to be below the long-term mean with a probability of 0.77. Catch limits that are considered precautionary for forage species simply because the limit is a small proportion of the species’ standing biomass may not be precautionary for their predators.

The genetic correlation between feed conversion ratio and growth rate affects the design of a breeding program for more sustainable fish production

Besson M, Komen H, Rose G, Vandeputte M. The genetic correlation between feed conversion ratio and growth rate affects the design of a breeding program for more sustainable fish production. Genetics Selection Evolution [Internet]. 2020 ;52(1). Available from: https://gsejournal.biomedcentral.com/articles/10.1186/s12711-020-0524-0
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Background

Most fish breeding programs aim at improving growth rate and include feed conversion ratio (FCR) neither in the breeding goal nor in the selection index, although decreasing FCR is known to increase farm profit and decrease environmental impacts. This is because FCR is difficult to measure in fish that live in groups and FCR is assumed to have a favourable (negative) genetic correlation with growth, although the magnitude of this correlation is unknown. We investigated the effect of the genetic correlation between growth and FCR on the economic and environmental responses of a two-trait breeding goal (growth and FCR), compared to a single-trait breeding goal (growth only). Next, we evaluated the weights to assign to growth and FCR in a two-trait breeding goal to maximize sustainability of fish production.

Methods

We used pseudo-best linear unbiased prediction (BLUP) index calculations to simulate a breeding program for sea bass. For the single-trait breeding goal, the trait in the breeding goal and in the index was thermal growth coefficient (TGC) and for the two-trait breeding goal, the traits in the breeding goal were TGC and FCR and the traits in the index were TGC and percentage of fat in the dorsal muscle (an indirect measure of FCR). We simulated responses to selection for genetic and phenotypic correlations between TGC and FCR ranging from 0 to − 0.8. Then, in the two-trait breeding goal, we calculated the economic return and the change in eutrophication when using economic values (EV) or environmental values (ENV).

Results

When the genetic correlation between TGC and FCR was lower than − 0.45, we found major differences in economic returns and in eutrophication between single and two-trait breeding programs. At a correlation of − 0.25, the two-trait breeding goal based on EV increased economic return by 25% compared to the single-trait breeding goal, while using ENV decreased eutrophication by 1.34% per ton of fish produced after one generation of selection.

Conclusions

The genetic correlation between TGC and FCR affects the magnitude of economic losses due to omitting FCR in the breeding program. In addition, the genetic correlation affects the importance of choosing EV or ENV to reduce eutrophication and increase profit.

Vulnerability of Demersal Fish Assemblages to Trawling Activities: A Traits-Based Index

de Juan S, Hinz H, Sartor P, Vitale S, Bentes L, Bellido JM, Musumeci C, Massi D, Gancitano V, Demestre M. Vulnerability of Demersal Fish Assemblages to Trawling Activities: A Traits-Based Index. Frontiers in Marine Science [Internet]. 2020 ;7. Available from: https://www.frontiersin.org/article/10.3389/fmars.2020.00044/full
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Reducing the impact on vulnerable species through changes in fishing practices, such as the spatial or temporal avoidance of certain areas, is key to increase the ecological sustainability of fisheries. However, it is often hampered by the availability of sufficiently detailed data and robust indicators. Existing trawl surveys are a cost-effective data source to assess the vulnerability of fishing areas based on the quantities of vulnerable species caught. We developed a biological traits-based approach to the vulnerability of demersal assemblages using commercial trawl catch data. An expert-based approach identified a set of biological traits that are expected to condition the species’ response to trawling impact and are combined to produce the vulnerability index ranked into four levels (low, moderate, high, and very high vulnerability). The approach was tested in four southern European fishing grounds showing evidence of over-exploitation, through catches being dominated by species of relatively low vulnerability to fishing impacts. The general distribution of species’ biomass amongst vulnerability groups was highly homogenous across case studies, despite local differences in fishing fleet structure, target species and fishing depths. Within all areas the species with moderate vulnerability dominated and, in most instances, species of “very high” vulnerability were not recorded. Nevertheless, differences emerged when comparing the proportions of highly vulnerable species in the catches. Variability in vulnerability level of the catch was also observed at small spatial scales, which was principally explained by differences in habitat type and depth and, secondarily, by fishing effort. In fine mud in the shallower areas there was a higher presence of low vulnerable fauna. Furthermore, vulnerable organisms decreased in their presence in sandier substrates on the continental shelf. The spatial heterogeneity in assemblage vulnerability composition encourages the potential for adoption of this index in the spatial management of fishing grounds aiming at ensuring a sustainable exploitation by mitigating trawl impacts on the most vulnerable components of the demersal assemblages.

Estimating maximum sustainable yield of snow crab (Chionoecetes opilio) off Tohoku Japan via a state-space assessment model with time-varying natural mortality

Shibata Y, Nagao J, Narimatsu Y, Morikawa E, Suzuki Y, Tokioka S, Yamada M, Kakehi S, Okamura H. Estimating maximum sustainable yield of snow crab (Chionoecetes opilio) off Tohoku Japan via a state-space assessment model with time-varying natural mortality. bioRxiv [Internet]. 2020 . Available from: https://www.biorxiv.org/content/10.1101/2020.02.02.931428v1
Freely available?: 
Yes
Summary available?: 
No
Type: Manuscript

Yield from fisheries is a tangible benefit of ecosystem services and sustaining or restoring a fish stock level to achieve a maximum sustainable yield (MSY). Snow crab (Chionoecetes opilio) off Tohoku has been managed by a total allowable catch since 1996, although their abundance has not increased even after 2011, when fishing pressure rapidly decreased because of the Great East Japan Earthquake. This implies that their biological characteristics, such as recruits, natural mortality coefficient (M), and terminal molting probabilities (p), might have changed. We developed “just another state-space stock assessment model (JASAM)” to estimate the MSY of the snow crab off Tohoku, Japan, considering interannual variations in M and p. The multi-model inference revealed that Mincreased from 0.2 in 1997 to 0.59 in 2018, although it was not different among the instars, sex, nor terminal molt of crabs. The parameter p also increased by 1.34–2.46 times depending on the instar growth stages from 1997 to 2018. We estimated the MSYs in three scenarios, which drastically changed if M and p were set as they were in the past or at the current values estimated from this study. This result indicated that the MSY of snow crab would also be time-varying based on their time-varying biological characteristics.

Links and Trade-Offs between Fisheries and Environmental Protection in Relation to the Sustainable Development Goals in Thailand

Sampantamit T, Ho L, Van Echelpoel W, Lachat C, Goethals P. Links and Trade-Offs between Fisheries and Environmental Protection in Relation to the Sustainable Development Goals in Thailand. Water [Internet]. 2020 ;12(2):399. Available from: https://www.mdpi.com/2073-4441/12/2/399
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

The fisheries sector significantly contributes to global food security, nutrition, and livelihood of people. Its importance for economic benefits, healthy diets, and nutrition, and achieving sustainable food systems is highlighted by several Sustainable Development Goals (SDGs), i.e., SDG 1 (No Poverty), SDG 2 (Zero Hunger), and SDG 14 (Life Below Water). However, due to unprecedented population levels, the contribution of the fisheries sector to fulfills these roles is challenging, particularly given additional concerns regarding environmental well-being and sustainability. From this perspective, this study aims to identify the links and trade-offs between the development of this sector and the environmental sustainability in Thailand via a critical analysis of their trends, current ecological impacts, and more importantly, their contributions to several individual SDGs. A time-series of Thailand’s fisheries production from 1995 to 2015 indicates a recent reduction from around 3.0 million tons in 1995 to 1.5 million tons in 2015 of wild fish and shellfish from marine and freshwater habitats. The maximum sustainable yield of these species has been exceeded. Conversely, Thailand’s aquaculture production has continued to grow over the last decade, resulting in a reduction of mangrove forest area, wild fish stocks, and water quality. While capture fisheries and aquaculture production significantly contribute to several SDG targets, there are potential trade-offs between their development and the achievement of SDGs within the planet dimension, i.e., SDG 6 (Clean Water and Sanitation), SDG 12 (Responsible Consumption and Production), SDG 13 (Climate Action), SDG 14, and SDG 15 (Life on Land). On the one hand, the mitigation of overfishing will be beneficial for the targets of SDG 14, leading to more sustainable resource management. On the other hand, it might cause a decrease in the volume of marine catches and economic and social profits. We conclude that the SDGs can serve as a framework for both policymakers and industrial workers to monitor and compromise on regulations that will optimize productivity in the context of sustainable development.

Protection reveals density-dependent dynamics in fish populations: A case study in the central Mediterranean

Melià P, Casagrandi R, Di Franco A, Guidetti P, Gatto M. Protection reveals density-dependent dynamics in fish populations: A case study in the central Mediterranean. PLOS ONE [Internet]. 2020 ;15(2):e0228604. Available from: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0228604
Freely available?: 
Yes
Summary available?: 
No
Type: Journal Article

Casting light on how the interaction between protection and density dependence affects fish population dynamics is critical for understanding the effectiveness of marine protected areas (MPAs). We developed a framework based on nonparametric statistics, model selection and multi-model inference to contrast alternative hypotheses about the effect of density dependence on demographic dynamics under protected and unprotected conditions. We trialed it using a 12-year long time series of white seabream (Diplodus sargus sargus) population density within the no-take zone of Torre Guaceto MPA (Italy) and at two nearby unprotected locations. Then, we showed how the demographic models obtained can be used to assess the consequences of protection on population viability. Population dynamics were significantly influenced by fish density within the MPA and at one of the unprotected locations, where demography is possibly driven by directional recruitment subsidy from the MPA. The comparison of population growth rates within and outside the MPA suggests that in unprotected conditions the fishery may remove a fraction between 40 and 70% of the population each year. The population viability analysis pointed out that, while the probability that the population becomes depleted (i.e. undergoes a local, temporary quasi-extinction) is high in unprotected locations, it is negligible within the no-take zone of the MPA.

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