Is it permissible to fish in the paddy field of another person?
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions, and all those who follow his footsteps until the Final day.
In Malaysia, fishing or trawling is among the methodologies employed to hunt animals that is permitted according to syarak, when it is done with ihsan (perfection/excellence). Its purpose is to benefit from the blessings that Allah SWT created for us as our sustenance and life’s supply for us to worship Him properly. Furthermore, in the Quran, Allah SWT states:
أُحِلَّ لَكُمْ صَيْدُ الْبَحْرِ وَطَعَامُهُ مَتَاعًا لَكُمْ وَلِلسَّيَّارَةِ
“Lawful to you is game from the sea and its food as provision for you and the travellers,” 
According to the above-presented question, fishing in another person’s paddy field or other owned areas without permission is prohibited in Islam. This prohibition is clear in al-Quran wear utilizing or using another’s without permission is an offence against the ownership of another person.
Allah SWT states:
وَلَا تَأْكُلُوا أَمْوَالَكُم بَيْنَكُم بِالْبَاطِلِ وَتُدْلُوا بِهَا إِلَى الْحُكَّامِ لِتَأْكُلُوا فَرِيقًا مِّنْ أَمْوَالِ النَّاسِ بِالْإِثْمِ وَأَنتُمْ تَعْلَمُونَ
“And do not consume one another’s wealth unjustly or send it [in bribery] to the rulers in order that [they might aid] you [to] consume a portion of the wealth of the people in sin, while you know [it is unlawful].” 
Syeikh Ahmad Mustafa al-Maraghiy stated in his commentary, “those who dare to consume the wealth of another and this leads to others following it and do the same, they are those who are unjust towards the property of others and it is a criminal offence.” 
It is clear from the verse, Allah SWT prohibits them from using, taking, transferring something that is owned by another without the permission of the owner.
However, there is a debate among scholars regarding this issue. Imam al-Nawawi stated in the chapter on food regarding the frits that fell from a tree, the ruling of the fallen fruits is the same as the ruling of the fruits on the tree (it is prohibited to take the fruits without getting the permission of its owner).
Whereas there are two rulings for the rulings of fruits that fall outside the gate. First, if it is customary in the area that the owner of the fruit trees doesn’t permit others to take his fruits that have fallen outside his gate, then it is prohibited to be taken. Second, if it is usual in the place and one is certain that the owner lets it, then it is halal and permissible. This is the asah opinion. 
The same for the case of fruits that have fallen outside the gate, scholars stated that if the fruits are owned by family members or close friends, but one is doubtful as to whether the owner let him take the fruits, then it is prohibited. However, if the person has a strong assumption (dzan) that the owner lets him take the fruits, then it is permissible on the condition that he takes the amount of which he thinks that the owner will let him take. 
Through the above discussion, then it is analogically deduced to the issue of fishing in another’s paddy field without permission. If according to the local custom that it is not an offence and he has a strong assumption that the owner doesn’t mind, then in this situation it is permissible. The reason is usually, the fishes in paddy fields are not specifically kept by the owner, consequently, they are fishes that came from nearby rivers or water channels going straight in the paddy fields. It is different if the paddy field is specially designed by its owner to be made into a specific fish farm. Likewise, it is prohibited if the owner clearly displays a no entry sign on his paddy field. In this issue, it is prohibited for one to trespass and if he is caught, it is an offence punishable by law if convicted.