Homelessness encampments affect fish populations in three primary ways:
- pollution of the waterway and nearby areas, like river banks
- physical modification of the waterway and nearby areas, through actions like cutting down tree limbs
- and poaching of fish.
Trash from an encampment off Hamilton Avenue in San Jose. Credit: South Bay Clean Creeks Coalition
For pollution, actions of concern include:
- washing people and pets in running water. This can involve using bath soap or body wash in a waterway.
- washing clothes and/or cooking implements in water. This can involve using dish soap, laundry detergent, bleach, and fabric softener in a waterway. Washing dirty clothes can lead to the disposal of feces in the waterway.
- people and pets relieving themselves or disposing of bodily waste like urine, feces, or vomit in a waterway. Fecal matter in the water can be directly infectious to people downstream. It can also add nutrients that promote eutrophication, an over-enrichment of a water body with nutrients like waste. The nutrients can be carried into wetlands as well as smaller tributaries like creeks and streams beyond a river. Eutrophication can make water quality inhospitable to salmonids.
- dumping debris and pollutants in or near water. Discarded objects and substances range from less harmful substances like dinner leftovers and plastic drink containers to extremely harmful substances like batteries and fuel for generators. This is especially a concern during the rainy season. Rainwater washes down slopes and can carry trash and belongings into a waterway.
- setting fires to cook food, keep warm, or commit acts of arson against people or property. This is especially a concern when extremely flammable items like lithium batteries or jerry cans of fuel ignite. Ash that washes into a river can negatively affect water quality. Large and persistent amounts of smoke can negatively affect plants and fish.
- when people engage in activities in an encampment that lead to sediment (soil) falling into the water, like removing dirt to create a path to the water, this often muddies fish habitats.
- camp activities like eating and storage of food and water can attract rats and other rodents like mice. Subsidizing rat populations increases the potential for rat and related disease transmission. It is unclear how such actions may directly impact fish. Yet the increase in rat populations can impact other species that use riparian corridors such as raptors and migratory birds.
- accidental or intentional disposal of personal belongings. This can occur when a person is intoxicated and does not notice or cannot protect their belongings during heavy rains or a rapidly developing situation like a flood. The likelihood of this action increases when people camp immediately adjacent to the low flow channel, on flat ground. People often do this because there is vegetative cover to hide from law enforcement.
For physical modification, actions of concern include:
- muddying gravel beds, which destroys a clean environment for fish to feed and impairs fish respiration.
- cutting or breaking limbs off trees or stripping leaves from them. This can lead to a reduction of shade over the waterway and the temperature of the water increasing. The hotter temperatures stress temperature-sensitive species. They may also decrease the amount of food available for such fish. Hotter temperatures can improve the chances of survival for less temperature-sensitive competitor species, especially invasive and introduced species.
- removing roots from trees near the waterway. This typically leads to erosion of river banks. It also leads to the sickliness and/or death of the trees.
- introducing foreign or invasive species of plants and animals into the waterway and nearby areas. This can lead to overgrowth or increased populations of the introduced species. It can reduce the amount of biodiversity in plants and subsequently, in animals, including fish.
- frequently walking on or around river banks or areas that are likely to erode. This changes the nature of the waterway because the soil can drop in, muddying the river bed.
- creating artificial or natural bridges using rocks, wood, and other materials. Such actions can block fish movement during low flow conditions. They can also temporarily increase sediment in the water, negatively affecting fish. Further, they can lead to more human activity in the water, like people crossing a stream. The presence of people traveling across or through the water can deter fish from gathering or traveling where people are, stopping fish at certain points, putting them under stress, and giving them less time to feed.
A barrier made of shopping carts and other materials off Cherry Avenue in San Jose. Credit: South Bay Clean Creeks Coalition
For poaching fish, actions of concern include:
- removing fish from the waterways, which leads to a direct reduction in fish populations.
- using metal, wood, or plastic objects or materials to create obstacles in the water that trap and/or harm fish. Such as dragging metal shopping carts into a stream and linking them with chains. This creates an improvised fish weir to trap and take fish.
- attempting and failing to catch fish in the waterways, but leaving the escaped fish injured and more susceptible to illness or consumption by predators.
- creating pools to catch fish using rocks, wood, and other materials. This can result in the taking of fish and increased likelihood of predation of fish by predators like raptors, raccoons, and coyotes, stress on the fish. Further, it can lead to increased rates of injury and poor health in fish, and prevent them from reaching their destination.