Overview

Comprehensive Description

Biology

A lacustrine, pelagic species. Males reproduce for the first time at 2-3 years, females at 3-4; most reproduce only once or twice. Spawns at temperatures above 15-16°C in June to August, along the shores near the surface at night with bright moonlights. Feeds mainly on cladocerans and copepods, also on small fish (Ref. 59043).
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Distribution

Range Description

Lakes Como, Garda, Orta, Maggiore, Lugano and Iseo (northern Italy, Switzerland). Introduced in Lakes Bolsena, Bracciano and Vico (central Italy).
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Europe and Mediterranean. Lakes Como, Garda, Orta, Maggiore, Lugano and Iseo (northern Italy, Switzerland). Introduced in Lakes Bolsena, Bracciano and Vico (central Italy).
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Lakes of Switzerland and northern Italy, introduced in central Italy.
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Physical Description

Size

Max. size

39.0 cm TL (male/unsexed; (Ref. 40637)); max. published weight: 760 g (Ref. 40637)
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Diagnostic Description

This species is distinguished from its congeners entering the freshwater of the Mediterranean basin by the following characters: an almost straight dorsal profile; thin gill rakers 38-72 (different populations average between 45 and 64); no teeth on palatine (Ref. 59043).
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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Habitat:
Lacustrine, pelagic.

Biology:
Males reproduce for the first time at 2-3 years, females at 3-4. Most individuals reproduce only once or twice. Spawns when temperatures rise above 15-16°C in June-August, along shores near surface at night in bright moonlight. Feeds predominantly on cladocerans and copepods but also consumes small fish.

Systems
  • Freshwater
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Environment

pelagic; non-migratory; freshwater
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Depth range based on 226 specimens in 1 taxon.
Water temperature and chemistry ranges based on 76 samples.

Environmental ranges
  Depth range (m): -9 - 133
  Temperature range (°C): 3.176 - 11.396
  Nitrate (umol/L): 1.852 - 8.971
  Salinity (PPS): 7.677 - 34.928
  Oxygen (ml/l): 0.982 - 7.828
  Phosphate (umol/l): 0.329 - 2.380
  Silicate (umol/l): 2.147 - 51.283

Graphical representation

Depth range (m): -9 - 133

Temperature range (°C): 3.176 - 11.396

Nitrate (umol/L): 1.852 - 8.971

Salinity (PPS): 7.677 - 34.928

Oxygen (ml/l): 0.982 - 7.828

Phosphate (umol/l): 0.329 - 2.380

Silicate (umol/l): 2.147 - 51.283
 
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Freyhof, J. & Kottelat, M.

Reviewer/s
Bogutskaya, N., & Smith, K. (IUCN Freshwater Biodiversity Unit)

Contributor/s

Justification
The species is known from Lakes Como (136 km²), Garda (355 km²), Orta, Maggiore (202 km²), Lugano (51 km²) and Iseo (58 km²) (northern Italy, Switzerland) where the stocks seem to be safe in all lakes. There are no known major threats to the species.
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Population

Population
Abundant.

Population Trend
Unknown
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Threats

Major Threats
No major threats known.
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Least Concern (LC)
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Management

Conservation Actions

Conservation Actions
No information.
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Wikipedia

Alosa agone

Alosa agone is a species of ray-finned fish in the genus Alosa. Alosa agone is an endangered species of the Alosa genus.[2]

Contents

Species Description

Alosa agone are common in the Mediterranean and the western Balkans.[2] There are also landlocked populations found in Italy.[2] The distribution of reproductive communities and the conservation status of Alosa agone in the central and eastern parts of the Mediterranean areas are poorly known.[2]

Conservation

Alosa agone’s numbers have declined due to barriers such as dams in their local areas. [2] These barriers prevent them from getting upstream to their spawning grounds and reproducing.[2] Improved water quality in some landlocked lakes have increased their numbers in recent years.[2]

Biology

The "twaite shad" are known to be very adaptive and variable as they form landlocked populations in Italy and its neighboring areas, including the western Balkans.[2] They can modify their morphology and biology according to their environment.[2] Therefore, Alosa agone, just like many Alosa species, can be either marine or freshwater fish.

References

  1. ^ Freyhof, J. & Kottelat, M. 2008. Alosa agone. In: IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. <www.iucnredlist.org>. Downloaded on 16 December 2011.
  2. ^ a b c d e f g h i Bianco, P. G. (2002), The Status of the Twaite Shad, Alosa agone, in Italy and the Western Balkans. Marine Ecology, 23: pp. 51–64. doi:10.1111/j.1439-0485.2002.tb00007.x
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