Variations in productivity of the Canary Current Large Marine Ecosystem and their effects on small pelagic fish stocks

Abstract Studies of small pelagic fish biomass are limited by the fact that research vessels and fishing boats are usually restricted to working areas with a bottom depth >20 m. Consequently, “unsampled” areas can represent a large proportion of the continental shelf, and the biomass in those areas can be important and must be taken into account in assessment methods in order to avoid misleading interpretations in population dynamics. A time-series ten years long has been compiled from acoustic-assessment surveys of small pelagic fish stocks, and the results show an overall increase in the acoustic fish density towards the coast, where values were the highest. Additional experiments on transects covering shallow-water areas (5–20 m) were conducted from 2001 to 2003 with small boats and a research vessel to evaluate the acoustic fish density in those areas. The results confirmed that the fish biomass in shallow water is significant, sometimes very large, and should be evaluated to avoid underestimation. Therefore, surveys should be conducted in shallow water, if at all possible, as well as at greater depths when carrying out surveys destined to support assessment exercises.

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Impact of Climate Variability on Small Pelagic Fish Stocks - a Comparative View

Investigaciones marinas ◽

10.4067/s0717-71782002030100069 ◽

2002 ◽

Vol 30 (1) ◽

Cited By ~ 1

Author(s):

Jürgen Alheit

Keyword(s):

Climate Variability ◽

Pelagic Fish ◽

Small Pelagic Fish ◽

Fish Stocks

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Foraging success in planktivorous fish increases with topographic blockage of prey distributions

Marine Ecology Progress Series ◽

10.3354/meps13343 ◽

2020 ◽

Vol 644 ◽

pp. 129-142

Author(s):

JM Aarflot ◽

P Dalpadado ◽

Ø Fiksen

Keyword(s):

Prey Availability ◽

Light Exposure ◽

Marine Ecosystem ◽

Planktivorous Fish ◽

Zooplankton Abundance ◽

Large Fish ◽

Foraging Success ◽

Fish Stocks ◽

Large Marine Ecosystem ◽

Bottom Depth

Banks and shelves are productive zones of the ocean, and often home to large fish stocks. Can shallower bottom topographies improve foraging opportunities for pelagic fish by blocking zooplankton from hiding in deep, darker water? We use mechanistic principles of visual prey search and an extensive dataset of zooplankton depth distributions to model foraging success in planktivorous fish across a large marine ecosystem. Our results show that zooplankton distribute deeper with deeper bathymetry, and that fish find exponentially less food with increasing bottom depths. Over shallow banks, zooplankton are forced into higher light exposure, providing higher prey encounter rates for fish despite lower abundance of prey. Stomach data analyses from a key planktivore support these predictions and suggest that fish foraging on copepods are more successful over shallower grounds. Our study demonstrates that prey availability for planktivorous fish is not proportional to zooplankton abundance, while the bottom depth is an important factor in fish foraging success and zooplankton mortality rates.

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EXPLOITATION AND CPUE TREND OF THE SMALL PELAGIC FISHERIES IN THE SULAWESI SEA, INDONESIA

Indonesian Fisheries Research Journal ◽

10.15578/ifrj.18.2.2012.63-69 ◽

2012 ◽

Vol 18 (2) ◽

pp. 63

Author(s):

Lilis Sadiyah ◽

Purwanto Purwanto ◽

Andhika P. Prasetyo

Keyword(s):

General Pattern ◽

Pelagic Fish ◽

Fish Stock ◽

Yield Model ◽

Small Pelagic Fish ◽

Fish Stocks ◽

Increasing Trend ◽

The Status ◽

Expected Benefits ◽

Pelagic Fisheries

One of the expected benefits of the Sulu-Celebes Sea Project during its implementation is to have increased fish stocks at demonstration sites, as indicated by the Catch per Unit of Effort (CPUE). Analysis of catch and effort data of the small pelagic fisheries by using the surplus yield model was done to obtain information on the likely trend of CPUE for the last ten years. By using the pajeko as the standardized fishing gear the trend of CPUE has been calculated. Between 2000-2005, the trend of production (catch), effort and CPUE followed the general pattern of the exploited fisheries that already fully exploited, where the increasing trend of effort was not followed by the increasing catch. On the other hand, the trend of CPUE is decreased. In the following years, the trend of both catch and CPUE do not follow the general pattern of the exploited fisheries. The trend of catch, effort and CPUE has likely been stable, indicating that the fishery in this period has been leveled-off. The status of exploitation of the small pelagic fish resources in the Indonesian Sulawesi Sea is demermined by the MSY level that has likely been surpassed during the period 2003-2004. Therefore with the increasing effort in the following year the trend of catch was relatively stable. It is likely that the small pelagic fish stock in the Indonesian Sulawesi Sea might be ‘fully exploited’.

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