MS: minimum size for mussum
20 cmMSParaguay (Pantanal)Paraná
In MS, mussum caught as bait in the wild must be at least 20 cm.
fishing forecast
marbled swamp eel
Synbranchus marmoratus · Synbranchidae · predator
Freshwater
Snake-shaped fish with no visible fins, which breathes air and spends the dry season buried in mud. A hardy live bait, used for large catfish.
Also called: mussum, muçum, peixe-cobra, enguia-d'água-doce
- common size
- 30–60 cm
- maximum
- 150 cm
- common weight
- 0.1–0.6 kg
- record/max.
- 4.0 kg
- depth
- 0–2 m
- ideal water
- 22–30 °C
fishing forecast
the right time
the right time
to be on the water
Choose the place and the species. The index, from 0 to 100, combines weather, sun, moon and tide with each fish's habits. Up to 28 days, with each day's confidence.
Reading the weather across 3 global models and 31 simulations…
0—
index Score from 0 to 100 for the fishing conditions of each hour. It reads weather, sun, moon, tide and the species' habits. It doesn't promise fish: it tells you when the water is on your side. 0–24 poor · 25–44 fair · 45–64 good · 65–84 very good · 85–100 excellent.
today
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confidence —
confidence How much you can trust the weather forecast for the day. It drops with distance and when the models disagree. It is not the chance of catching fish.
models and trend Up to 16 days, three global weather models (the European ECMWF, the American GFS and a high-resolution blend) read hour by hour; when they disagree, the light band on the chart widens. Beyond that it's a trend: 31 runs of the American GEFS model. Confirm when it's 1 week out.
window Consecutive hours with the index near the day's peak and no danger alert. It is the time to have the bait in the water.
hour by hour
slide your finger or mouse over the chart to see each hoursee hour-by-hour table
why this index at —?
next 7 days
chart: bar height = day's index · line = variation between models · striped = trend · fainter = less confidencechoose the day
Each card shows the day's index (0 to 100) and, below it, a strip with the index for each hour, from 0h to 23h. from poor to excellent.
4-week calendar
the fishing month at a glance
plan a trip
what's the best window for the crew?
Choose how many fishing days. We compare each stretch by its average index, discount days with a warning or closed season, and show the 3 best.
trend for the coming weeks
Line: the middle value of 31 simulations of the American GEFS model. Band: where 8 out of 10 fall. Narrow, firm trend; wide, high uncertainty.
the species
everything about the marbled swamp eel
overview
who is the marbled swamp eel
Round, smooth-bodied fish, resembling a snake or eel, but not closely related to them. Lives in swamps, ditches, rice fields, lagoons and river edges, in clear or murky water, and is active at night, eating fish, shrimp, worms and insects. Breathes air when needed and, when water drops, digs tunnels into mud or banks and waits for the flood, still active; that is why it disappears from fish surveys in many places. It is hermaphroditic: born female, and some fish later become male; the male guards eggs in a nest or burrow. As bait, it stays alive on the hook for a long time, which makes it popular for catfish fishing. It ranges from Mexico to northern Argentina.
fun facts
- It breathes air through its mouth and throat and can stay buried in the mud for months waiting for the water to return.
- It is hermaphroditic: born female, and some fish turn male.
how to recognize it
identification
Cylindrical, very long body, smooth and slippery, with no pectoral or pelvic fins; dorsal and anal fins reduced to a skin fold near the tail. A single gill opening, a slit under the throat. Small eyes. Olive-brown to yellowish, with dark marbled spots. The tuvira is flattened on the sides and has a long anal fin; the poraquê is much bigger and also has a long anal fin.
distribution
open on the large map where found
From Mexico to northern Argentina, including Cuba and Trinidad. In Brazil, in swamps, várzeas and rivers of nearly all basins; it also tolerates brackish water.
Habitat: Swamps, ditches, rice paddies, bays and river edges with mud and vegetation; in the dry season, buried in tunnels.
native to the basins
AmazonTocantins-AraguaiaWestern Northeast AtlanticParnaíbaEastern Northeast AtlanticSão FranciscoEast AtlanticSoutheast AtlanticParanáParaguay (Pantanal)UruguaySouth Atlantic
states
Amazonas, Pará, Mato Grosso, Mato Grosso do Sul, Goiás, Minas Gerais, São Paulo, Paraná, Santa Catarina, Rio Grande do Sul, Bahia, Pernambuco, Ceará, Maranhão, Tocantins
when to fish
best season
time of year
JanFebSeaAprMayJunJulAugSepOctNovDec
Found all year; in severe drought it stays buried and disappears from view.
best time of day
Nighttime. Active at night; by day it stays in its burrow or in the mud.
what affects the marbled swamp eel
sensitivity The little bars show how much each factor affects this species. Five full: it feels it a lot.
sensitivity The little bars show how much each factor affects this species. Five full: it feels it a lot.
cold and cold fronts
Cold reduces activity.
atmospheric pressure
Little effect.
moon
Little known effect.
rain
Rain that fills the swamps brings it out of its burrow.
water level
In the dry season it digs tunnels in the mud and waits for the flood.
noise
Not very sensitive.
wind
Little effect.
depth
Shallow, on the muddy bottom and along the bank.
how to fish
- rod
- bamboo cane or telescopic rod, 2 to 3 m
- spinning / baitcasting reel
- optional
- line
- monofilament 0.25 to 0.30 mm
- leader
- optional
- hook
- #6 to 10
natural baits
- minhoca
- piece of fish
accessories
- cloth or sand to hold the slippery fish
- bucket with lid
tip from an angler
As bait, pass the hook through the mouth or the skin of the back, without piercing the body: it lasts for hours alive.
rules for the marbled swamp eel
Summary of the regulations we found, with the source for each. Rules change; before keeping or transporting fish, check with the state environmental agency.
Conservation: Not on the national list of threatened species (Portaria GM/MMA nº 1.667/2026).
MS: commercial bait catch only by professionals
licensed professional fisher; amateur without cast net or netMSParaguay (Pantanal)Paraná
In MS, catching mussum as live bait for sale may only be done by licensed professional fishers, with an Imasul permit and transport slip. Amateur anglers and riverside residents may not use cast nets or mesh gear to catch bait. Catching is banned within 200 m of waterfalls, rapids, springs and confluences, and within 1,000 m of dams and nesting colonies. During the spawning closure, commercial bait catch reopens only from February 20.
piracema closures in the basins where the species lives
Spawning closure (piracema) in the Paraná River basin
01/11 to 28/02SPPRMGGOMSDF
Allowed: Recreational fishing only for non-native species and hybrids (peacock bass, tilapia, black bass, carp, croaker, etc.; piauçu remains prohibited), with handline, simple pole, or rod with spinning or baitcasting reel, up to 10 kg + 1 fish. In rivers, from shore only; in reservoirs, from a boat or from shore. Prohibited: floodplain lakes, aquatic-animal bait, within 1,500 m of dams and waterfalls, and within 500 m of confluences. Tournaments only in reservoirs and only with non-native species.
Source: IN IBAMA nº 25/2009
Spawning closure (piracema) in Minas Gerais (state rule)
01/11 to 28/02MG
Allowed: Only exotic or hybrid species, 3 kg + 1 fish per day, with handline, rod, simple pole, or spinning or baitcasting reel. Nets prohibited. Keep the minimum distances from dams and reservoirs.
Source: Portarias IEF nº 154/2011 (São Francisco), 155/2011 (East) and 156/2011 (Grande/Paranaíba)
Closed season in Goiás (state rule)
01/11 to 28/02GO
Allowed: Sport and guided fishing only in reservoirs, catch and release with barbless hooks (no keeping, transporting or eating). Subsistence: up to 5 kg per day, for household consumption only.
Spawning closure (piracema) in the Pantanal of Mato Grosso do Sul
05/11 to 28/02MS
Allowed: Subsistence fishing by riverside residents and authorized scientific fishing. Decree 15.166/2019 (art. 11, §5) allows catch and release only in February and only in the channels of the Paraguay and Paraná rivers. For the rest of the period, not even catch and release is allowed. Check the Imasul portaria for each season.
Source: Decreto estadual MS nº 15.166/2019, art. 11; IN IBAMA nº 201/2008
Spawning closure (piracema) in Mato Grosso (all basins)
01/10 to 31/01MT
Allowed: All fishing modalities are prohibited in rivers, including catch and release (Law 9.096/2009, art. 19-A). Exceptions: subsistence fishing from shore (3 kg or 1 fish, no transport or sale) and scientific fishing. Law 13.159/2025 now allows licensed sport fishing in UHE/PCH hydropower reservoirs, natural lakes and border rivers, subject to a scientific study and a license from the environmental agency. We have not confirmed whether these licenses are already being issued.
Spawning closure (piracema) in the Araguaia River basin
01/11 to 28/02GOTOPAMT
Allowed: Recreational fishing only in reservoirs, with handline, rod, or spinning or baitcasting reel. Fish may only be eaten on site, not transported. Competitions prohibited. Subsistence: 3 kg + 1 fish. State rules (GO and TO) may be stricter.
Spawning closure (piracema) in the Tocantins and Gurupi river basins
01/11 to 28/02TOPAMAGO
Allowed: Recreational fishing only in reservoirs, with on-site consumption. Subsistence: 5 kg + 1 fish. State rules may be stricter.
Spawning closure (piracema) in Tocantins (state rule)
01/11 to 28/02TO
Allowed: In 2025/26: catch and release with barbless hooks and recreational fishing card; subsistence fishing on foot or from a rowboat, with simple pole or handline.
Source: Portaria Naturatins nº 244/2025 (2025/26 season); INIs MPA/MMA nº 12 and 13/2011
Spawning closure (piracema) in the São Francisco River basin (rivers and reservoirs)
01/11 to 28/02MGBAPEALSEGODF
Allowed: Recreational fishing from a boat or from shore with handline, rod, spinning or baitcasting reel, up to 5 kg + 1 fish. Prohibited within 1,000 m of dams, waterfalls and rapids, and within 500 m of confluences. Floodplain lakes have a longer closed season (see next item).
Source: Portaria IBAMA nº 50/2007
São Francisco: floodplain lakes
01/11 to 30/04MGBAPEALSEGODF
Allowed: No fishing in the floodplain lakes during the period.
Source: Portaria IBAMA nº 50/2007
Spawning closure (piracema) in the Uruguay River basin
01/10 to 31/01RSSC
Allowed: Recreational fishing from shore, or from a boat without motor. Only handline or rod, line and hook, one gear per angler, up to 5 kg. Prohibited in floodplain lakes, within 1,500 m of dams, within 500 m of confluences, and in stretches listed in the rule (e.g., Turvo River).
Source: IN IBAMA nº 193/2008
Spawning closure (piracema) in the southern basins (RS and SC, outside the Uruguay)
01/11 to 31/01RSSC
Allowed: Recreational fishing from a boat or from shore, with a single hook, one gear per angler, up to 5 kg.
Source: IN IBAMA nº 197/2008
Spawning closure (piracema) in the Southeast basins
01/11 to 28/02ESMGRJSPPR
Allowed: In rivers, shore fishing only; in reservoirs, from a boat or from shore. Only non-native species, hybrids, and giant river prawn (camarão-gigante-da-malásia), up to 10 kg + 1 fish. Prohibited in floodplain lakes and within 1,000 m of dams.
Source: IN IBAMA nº 195/2008
Spawning closure (piracema) in the East basins
01/11 to 28/02BAESMGSE
Allowed: Same rules as the Southeast basins: only non-native species and hybrids, up to 10 kg + 1 fish; in rivers, shore fishing only.
Source: IN IBAMA nº 196/2008
Spawning closure (piracema) in the Parnaíba River basin
15/11 to 16/03PIMACE
Allowed: Recreational fishing from a boat or from shore with handline, rod, spinning or baitcasting reel, up to 5 kg + 1 fish per day. Prohibited within 1,500 m of dams, waterfalls and rapids. Competitions prohibited.
Source: IN MMA nº 40/2005
Closed season in the Maranhão basins
01/12 to 30/03MA
Allowed: Recreational fishing from a boat or from shore with handline or rod, up to 5 kg or 1 fish. Transport only within the municipality. Competitions prohibited.
Source: Portaria IBAMA nº 85/2003
Closed season in the Ceará basins
01/02 to 30/04CE
Allowed: Recreational fishing with handline or rod is outside the prohibition.
Source: Portaria IBAMA nº 04/2008
Closed season in the rivers of Marajó Island (PA)
01/01 to 30/04PA
Allowed: The same recreational-angler exceptions as in Portaria 48/2007 apply (handline or rod, 5 kg + 1 fish), unless a stricter state rule applies.
Source: Portaria IBAMA nº 48/2007
Closed season in the Amazon basin in Amapá
15/11 to 15/03AP
Allowed: Recreational anglers with handline or rod, line and hook are outside the Annex II prohibitions, with a bag limit of 5 kg + 1 fish, unless a stricter state rule applies.
Source: Portaria IBAMA nº 48/2007
Closed season in Roraima
01/03 to 30/06RR
Allowed: Subsistence fishing only.
Source: Portaria IBAMA nº 48/2007
Border rivers MT/RO and MT/PA
05/11 to 28/02MTROPA
Allowed: See the exceptions in Portaria 48/2007 and the state rules for each bank.
Source: Portaria IBAMA nº 48/2007
catch and release
catch and release Releasing the fish alive, quickly and with a wet hand. During a closed season it isn't always allowed: what the regulation says applies.
catch and release Releasing the fish alive, quickly and with a wet hand. During a closed season it isn't always allowed: what the regulation says applies.
Leftover bait must go back to the same swamp or river it came from.
in the kitchen
Rarely eaten; its main use is as bait.
how much it weighs without taking it out of the water
Length-weight relationship W = a·Lb (a = 0.00091, b = 3.08; FishBase). It's an average: a fat or lean fish can vary by 10% to 20%.
estimated weight
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sources and references
The season weights (months), the time of day and the sensitivities (cold, pressure, moon, wind, rain, tide, strong light, murky water and noise) are the app's editorial estimates, based on the literature below and on the field experience of anglers and guides. They are not official data nor a measurement made for this species, and they may vary by region and year. Closed seasons and legal rules appear in the rules section, with the norm and a link.
- scientific FishBase — Synbranchus marmoratus (ficha da espécie)Distribution, biology (air breathing, burrows in the dry season, hermaphroditism), length-weight relationship and country list. The app's maximum weight was estimated from the length-weight relationship for the maximum length. Page checked on Oct 13, 2026.
- scientific IUCN Red List — Synbranchus marmoratus (avaliação global: Pouco Preocupante, LC, 28/03/2018)Global assessment. Link given on the FishBase entry (Red List, version 2025-2).
- official Portaria GM/MMA nº 1.667, de 27 de abril de 2026 — Lista Nacional Oficial de Espécies da Fauna Ameaçadas de Extinção (peixes e invertebrados aquáticos)The species is not on the list (checked against the text published in the DOU of 28/04/2026, section 1, p. 96).
- official Resolução SEMAC-MS nº 3/2011 (com a redação da Resolução SEMAC nº 22/2011) — captura, transporte, comércio e cultivo de iscas vivas em MSMinimum sizes of live baits, commercial catch only by professional fishers, distances and permitted gear. Imasul text checked on Oct 13, 2026.
- official Lei estadual MS nº 2.898/2004 — iscas vivasLive bait catch only by licensed professional fishers; banned below minimum size and during spawning; in the Alto Paraguay, only baits native to the basin. Page checked on Oct 13, 2026.
- official Portaria MPA nº 532, de 23 de setembro de 2025 — nomes comuns das espécies de peixes de interesse comercialOfficial names: mussum, muçum. Page checked on Oct 13, 2026.
similar species
how we calculate
where each number comes from
The weather comes from three independent global models, cross-checked hour by hour: when they agree, confidence goes up; when they diverge, the band between them shows on the chart. Beyond 16 days, we use the GEFS ensemble of 31 simulations: if 20 of the 31 predict rain, the chance of rain is 65%. Sun and moon are calculated astronomically, with no uncertainty.
The index adds up, weighted for each species: time of day (species curve anchored to real sunrise and sunset), moon (transits, rise and set, phase), pressure (3 h trend and 24 h swing), water temperature (in rivers, estimated from air temperature; at sea, estimated by an ocean model), wind, rain, clouds, tide and the month in the species' cycle.
sources for this lookup
how accurate the forecast is
Accuracy measured in the reference project (4 regions, 93 days, forecast vs. observed): maximum temperature is off by 0.6 °C on average the next day and 1.7 °C at 7 days; rain of 5 mm or more is detected 76% of the time the next day and 57% at 7 days. Detection isn't everything: the false alarm rate isn't published here yet, and 93 days in 4 regions is still a small sample. We now also measure every day, at the app's destinations: