Reply to Ziegler et al. “Adding perspectives to: Global trends in carbon dioxide (CO2) emissions from fuel combustion in marine fisheries from 1950-2016” and addressing concerns of using fishing effort to predict carbon dioxide emissions

Greer, Krista; Zeller, Dirk; Woroniak, Jessika; Coulter, Angie; Winchester, Maeve; Palomares, M.L.D.; Pauly, Daniel

doi:10.1016/j.marpol.2019.03.004

Cited by 7 publications

(7 citation statements)

References 6 publications

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“…This ensured comprehensive coverage of all small-scale fishing in each country and territory. Estimating broad-scale fishing effort based on indirect methods such as used here relies on assumptions that, no matter how carefully and conservatively made, are inherently uncertain, which has generated some debate in regards to the potential accuracy of the data (Greer et al, 2019b;Ziegler et al, 2019). However, our extensive use of a range of available fishing capacity parameters sourced at the fisheries-and country-level may provide some advantages over more generalized estimation techniques, and is thought to provide a reasonable representation of the fishing effort trends in the region over time.…”

Section: Discussionmentioning

confidence: 99%

Fishing Effort and Associated Catch per Unit Effort for Small-Scale Fisheries in the Mozambique Channel Region: 1950–2016

et al. 2021

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The Mozambique Channel region in East Africa has diverse marine ecosystems and serves as a migratory corridor for economically important species. Local and foreign industrial fisheries operate in the Mozambique Channel, but regional small-scale fisheries are the crucially important fisheries that provide food security, livelihoods, and economic opportunities for rural coastal communities. This study reconstructed and investigated trends in the fishing effort and catch per unit effort (CPUE) of small-scale marine fisheries in four Exclusive Economic Zones (EEZ) that constitute the Mozambique Channel, i.e., Union of Comoros, Madagascar, Mayotte, and Mozambique, from 1950 to 2016. Effective fishing effort for small-scale fisheries in the form of fishing capacity in kWdays (i.e., kilowatt days) was derived using the number, length, motorization (engine power) by fishing vessels, as well as an approximate human-powered equivalent for shore-based fishers without vessels, as well as days of fishing per year. Effective small-scale fishing effort in the Mozambique Channel increased by nearly 60 times from just over 386,000 kWdays in 1950 to over 23 million kWdays in 2016. Correspondingly, the overall small-scale CPUE, based on previously and independently reconstructed catch data declined by 91% in the region as a whole, from just under 175 kg⋅kWday–1 in the early 1950s to just over 15 kg⋅kWday–1 in recent years. All four EEZs showed the strongest declines in the small-scale CPUE in the earlier decades, driven by motorization and growth in vessel numbers impacting effective fishing effort. Increased motorization combined with a substantial growth in overall vessel numbers were the drivers of the increasing fishing effort and decreasing CPUE, and clearly suggest that continuing to increase the fishing capacity of small-scale fisheries in the absence of effective and restrictive management actions may exacerbate overexploitation risk.

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Section: Discussionmentioning

confidence: 99%

Fishing Effort and Associated Catch per Unit Effort for Small-Scale Fisheries in the Mozambique Channel Region: 1950–2016

et al. 2021

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“… 30 for 1990–2010. To estimate an overall trend of number of fishing vessels for the 1950–2010 period, for those countries with missing years, we assumed same trends as observed by Greer 31 who reported the number of fishing vessels for each country of the world for 1950–2010. GT was extrapolated, for the missing years, as the average ratio of GT in the observed time periods, while number of days spent fishing were kept as the ratio of days at sea observed respectively in Sacchi et al .…”

Section: Methodsmentioning

confidence: 99%

Historical changes of the Mediterranean Sea ecosystem: modelling the role and impact of primary productivity and fisheries changes over time

Piroddi

Coll

Liquete

et al. 2017

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151

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The Mediterranean Sea has been defined “under siege” because of intense pressures from multiple human activities; yet there is still insufficient information on the cumulative impact of these stressors on the ecosystem and its resources. We evaluate how the historical (1950–2011) trends of various ecosystems groups/species have been impacted by changes in primary productivity (PP) combined with fishing pressure. We investigate the whole Mediterranean Sea using a food web modelling approach. Results indicate that both changes in PP and fishing pressure played an important role in driving species dynamics. Yet, PP was the strongest driver upon the Mediterranean Sea ecosystem. This highlights the importance of bottom-up processes in controlling the biological characteristics of the region. We observe a reduction in abundance of important fish species (~34%, including commercial and non-commercial) and top predators (~41%), and increases of the organisms at the bottom of the food web (~23%). Ecological indicators, such as community biomass, trophic levels, catch and diversity indicators, reflect such changes and show overall ecosystem degradation over time. Since climate change and fishing pressure are expected to intensify in the Mediterranean Sea, this study constitutes a baseline reference for stepping forward in assessing the future management of the basin.

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“…In the present study we used human population time series to inform marine catch estimates for the artisanal and subsistence sectors. Data for the human population in the Socotra Archipelago could be sourced for , 2003for , 2011for , 2014. Linear interpolation was used to derive estimated population levels for years without data.…”

Section: Human Populationmentioning

confidence: 99%

“…The method for reconstructing boat-based and shore-based small-scale fishing effort for the Socotra Archipelago was adapted from Greer (2014) and Zeller et al (2021). Nominal fishing effort was derived by multiplying the number of fishing boats by their engine power (in kW), depending on their length class and motorization level (Supplementary Table S4).…”

Section: Fishing Effort Of Small-scale Fisheriesmentioning

confidence: 99%

Small-scale fisheries catch and fishing effort in the Socotra Archipelago (Yemen) between 1950 and 2019

et al. 2023

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The Socotra Archipelago (Yemen), a group of four islands off the north-eastern tip of Africa in the western Indian Ocean, has a population that relies heavily on small-scale fishing for livelihoods and food security. However, the reporting of fisheries catches by Yemen has consistently been incomplete, with artisanal (small-scale, commercial) catches underreported and small-scale non-commercial subsistence and recreational catches not reported at all. Here, we reconstruct the total small-scale catches and fishing effort from the waters of the Socotra Archipelago for 1950 to 2019, and derive catch-per-unit-effort (CPUE) estimates for these fisheries. The catch officially reported by the Food and Agriculture Organization on behalf of Yemen that was assumed taken from the archipelago is thought to be around 20% of the total reconstructed catch for the archipelago. The reconstructed small-scale catch increased from ~1,500 t in 1950 to an all-time peak of 12,000 t in 2000 before declining to 3,300 t by 2014. Thereafter, catches increased again slightly to just over 3,700 t·year-1 by 2019. Artisanal catches accounted for around 70% of total small-scale catches prior to 2010, but made up only around 46% by 2019. Conversely, subsistence catches increased from ~1,000 t in 2010 to ~2,000 t in 2019, and accounted for 54% of total catches by 2019. Small-scale fishing effort increased by over 1000% since 1950 and reached over 11 million kWdays by 2019. The CPUE derived for small-scale fisheries declined by 78% since 1950, from 1.4 kg·kWday-1 to 0.3 kg·kWday-1 in 2019, with most of the decline occurring after 2000. Our findings suggest resource overexploitation, and may assist efforts to more sustainably manage the Socotra Archipelago’s fish stocks. Small-scale fisheries support food and nutrient security of the local population, not least during political and humanitarian crises such as in Yemen.

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Reply to Ziegler et al. “Adding perspectives to: Global trends in carbon dioxide (CO2) emissions from fuel combustion in marine fisheries from 1950-2016” and addressing concerns of using fishing effort to predict carbon dioxide emissions

Cited by 7 publications

References 6 publications

Fishing Effort and Associated Catch per Unit Effort for Small-Scale Fisheries in the Mozambique Channel Region: 1950–2016

Fishing Effort and Associated Catch per Unit Effort for Small-Scale Fisheries in the Mozambique Channel Region: 1950–2016

Historical changes of the Mediterranean Sea ecosystem: modelling the role and impact of primary productivity and fisheries changes over time

Small-scale fisheries catch and fishing effort in the Socotra Archipelago (Yemen) between 1950 and 2019

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