Few studies have been done on the interspecific relationship between fishes species， an important part of mangrove wetlands. In 2022-2023， a sampling survey was conducted on the mangrove tidal gully fish in the estuary area of Haishan Town， Raoping County， Guangdong Province in spring， summer， autumn and winter， and the composition of fish species in the mangrove wetland was studied. The aim of this study was tried to elucidate the response relationship between the distribution and interspecific relationships of wetland fish and the effects of environmental factors by calculating the spatiotemporal niche width and interspecific overlap values. The results showed that a total of 14 species belonging to 12 families and 6 orders were identified ， including 6 dominant species （IRI≥500）， 3 common species （500

>

IRI≥100）， 2 rare species （100

>

IRI≥10） and 3 occasional species （IRI

<

10）. The spatiotemporal niche width of the fish in mangrove tidal gullies ranged from 0.000 to 2.428， with a large variation range， including 1 species of wide niche species （

B

ij

≥2.0） （

Oreochromis niloticus

）， 2 species of medium niche species （1.0≤

B

ij

<

2.0）（

Odontamblyopus rubicundus

and

Bostrichthys sinensis

）， and the remaining 11 species narrow niche species （0

<

B

ij

<

1.0）. The spatiotemporal niche overlap value between the fish species in the tidal gully of seamount mangrove forest was 0.000-0.956， again with a large variation range， among which 43 pairs （

>

0.6） were highly significant overlapped （0.6）， accounting for 47% of the total logs， and 21 pairs （0.3

<

overlap value

<

0.6） were significant overlapped

， accounting for 23% of the total logs， and the two pairs accounted for 70% of the total logs. The highest spatiotemporal niche overlap values were found in

Siganus oramin

and

Periophthalmus cantnensis

（up to 0.956）， while the lowest non-overlap values were included in

O. niloticus

and

Platycephalus indicus

，

B. sinensis

and

P. indicus

， and

Paraplagusia bilineata

and

P. indicus

， all with the value of 0. BIOENV analysis showed that the most suitable combinations of environmental factors for fish abundance in the study area were water temperature， salinity， pH and chlorophyll a content， which the correlation coefficient is 0.475， and the RELATE test results were significant （

R

= 0.461，

P

<

0.05）， indicating that these four environmental factors were important in affecting fish distribution. In general， the spatiotemporal niche of fish in the mangrove wetland of Raoping Haishan town was dominated by narrow niche species， and the spatiotemporal niche overlap between different fish species was significant and meaningful. The water temperature， salinity， pH and chlorophyll a content of the water body were important environmental factors affecting the distribution of fish in the wetland in the forest area.