The Pollution Problem Of Bay Scallops

Bay scallops are bivalve mollusks of the family Pectinidae, found in the Atlantic waters of the United States. They are a popular seafood item, known for their sweet and tender meat. However, their populations have been declining due to various factors, including fishing, climate effects, disease, pollutants, and sediment runoff from farming and forestry. Forest and Bird have listed scallops as the Worst Choice in their Best Fish Guide for sustainable seafood species. This article will explore the issue of pollution in bay scallops and its impact on their populations and the environment.

Scallop population decline due to pollution

Scallops are a family of bivalve mollusks found in all the world's oceans, except freshwater. They are a popular food source, with the two most common types being bay scallops and sea scallops. Bay scallops are smaller, sweeter, and more affordable than sea scallops. They are found in the cold, shallow waters of East Coast estuaries and bays in the United States.

However, the population of bay scallops has been declining due to various factors, including pollution. One of the main causes of the decline in bay scallop numbers is the reduction of seagrasses in their habitat. Bay scallops attach themselves to seagrasses, such as eelgrass, during their larval process. When toxicity depleted the eelgrass beds, likely due to nutrient runoff, the bay scallop population suffered. This issue was particularly prominent during the brown tide scourge in the 1980s, which affected the northeastern bays where bay scallops are commonly found.

In addition to pollution, other factors contributing to the decline in bay scallop numbers include fishing, climate change impacts, disease, sediment runoff from farming and forestry, and overfishing of sharks, a predator of the scallops' main predator, stingrays. The combination of these factors has led to a significant decrease in bay scallop populations, particularly on the East Coast of the United States.

The sustainability of scallop harvesting practices has also come into question. While diver scallops, which are hand-harvested by divers, are considered more sustainable and selective, they are also more expensive. Most commercially sold scallops are harvested by trawling, which involves scraping the ocean floor and can be more damaging to the environment. Additionally, the largest wild scallop fishery, for the Atlantic sea scallop, is found off the northeastern United States and eastern Canada, contributing to the pressure on bay scallop populations in these regions.

To promote the recovery of bay scallop populations, organizations like Seafood Watch offer recommendations for consumers. They suggest buying bay scallops from Massachusetts or New York, where they are farmed using more sustainable bottom culture methods. By choosing sustainably sourced scallops and supporting conservation efforts, consumers can play a role in ensuring the long-term viability of bay scallop populations and reducing the impact of pollution and overfishing on these delicate marine organisms.

Shark killings and overfishing

Bay scallops are considered a delicacy by many, and their sweet and tender meat is highly sought after. However, their populations have been declining due to various factors, including fishing, climate effects, disease, pollutants, and sediment runoff. One of the main factors contributing to the decline in bay scallop populations is the reduction of sharks due to overfishing.

Sharks are apex predators that play a critical role in maintaining healthy ocean ecosystems. They occupy the top of food webs and help keep these webs stable. Overfishing of sharks has led to a decline in their populations, which has had a ripple effect on other species in the ocean, including bay scallops.

Sharks are particularly vulnerable to overfishing due to their slow rate of reproduction. They are also subjected to relentless fishing pressure, with fishermen targeting their meat, fins, liver oil, skin, cartilage, teeth, and jaws. Additionally, sharks are threatened by habitat destruction caused by intensive fishing methods such as bottom trawling, which destroys vital habitats like coral reefs.

The impact of shark overfishing is evident in the decline of bay scallop populations. Sharks are known to feed on stingrays, which are the main predators of bay scallops. With the reduction of shark populations due to overfishing, the stingray population has been able to thrive, leading to a decrease in the number of bay scallops.

To address the issue of shark overfishing and its impact on bay scallop populations, conservation efforts are necessary. This includes reducing the number of sharks killed and implementing sustainable fishing practices. Additionally, further research into shark behavior, breeding habits, and migration patterns is needed to develop effective conservation measures. By understanding the complex relationships between different species in the ocean, we can work towards preserving the delicate balance of marine ecosystems and ensuring the sustainability of resources like bay scallops.

Metal pollution in farmed scallops

Scallops are one of the most common bivalves, large-scale farmed in the coastal areas of China. They are also found in the Atlantic waters, from Texas and Florida to the Northeast. Over the last 100 years, the populations of bay scallops on the East Coast of the United States have greatly diminished due to several factors, including fishing, climate effects, disease, pollutants, and sediment runoff from farming and forestry.

Three species of scallops (Chlamys farreri, Argopecten irradians, and Patinopecten yessoensis) from 10 sample sites along the Bohai Sea and the Yellow Sea were collected to investigate species-specific and tissue-specific bioaccumulation, spatial-temporal distribution, and health risks for people. Cd concentrations in 96% of scallop samples exceeded the standard, with the highest Cd bioaccumulation potentials (BCF) >10,000. The metal pollution index values showed that A. irradians could accumulate more metals than the other two species, and scallops in the Bohai Sea were more polluted by heavy metals than in the Yellow Sea.

The capacities of tissues in scallops to accumulate metals generally followed the order of the digestive gland, gill, and adductor muscle. Adults and children face non-cancer risks due to Cd accumulation in scallops, which accounts for 85% of the total hazard quotient and 48% of the total cancer risk. Scallops can accumulate Cd rapidly from ambient environments, causing health risks. The recommended maximum edible amounts of whole scallops are 127/63 g/week for adults/children.

Sources of heavy metals in seafood include fossil energy consumption (coal combustion and vehicle exhaust), seawater, and metallurgic dust. Policies controlling fossil-energy and clean coastal water actions are beneficial to seafood safety by reducing target heavy metals in seafood.

Nutrient runoff from coastal development

Agricultural runoff is a primary contributor to nutrient pollution in coastal areas. Fertilizers and animal manure from farms contain high levels of nitrogen and phosphorus, which, when introduced into aquatic systems, can lead to eutrophication. Eutrophication occurs when there is an over-enrichment of nutrients, causing an excessive growth of algae. This process depletes oxygen levels in the water, leading to fish kills and disruptions in the food chain. Additionally, increased nutrient inputs can favour the growth of macroalgae at the expense of corals, further damaging marine ecosystems.

Industrial activities also play a role in nutrient runoff. The production and use of synthetic nitrogen fertilizers, as well as fossil fuel combustion, release large amounts of reactive nitrogen into the environment. This nitrogen eventually makes its way into coastal waters, contributing to the eutrophication process. Moreover, industrial emissions and wastewater discharges can introduce toxic chemicals and contaminants into estuaries and oceans, further degrading water quality.

The impacts of nutrient runoff extend beyond environmental concerns. Coastal communities rely on healthy estuarine environments for protection from flooding and erosion. When nutrient pollution weakens these ecosystems, the infrastructure, economy, and resilience of these communities become vulnerable to additional stressors. This is particularly relevant in the context of climate change, as more frequent and severe storms can intensify nutrient runoff and erosion, creating a cycle of degradation.

To address the issue of nutrient runoff from coastal development, various strategies are being employed. Large-scale restoration projects aim to reduce nutrient loading in affected areas, such as the Gulf of Mexico and Chesapeake Bay. The implementation of best management practices and modelling tools helps mitigate nutrient and sediment reduction. Additionally, strategic crop locations, buffer zones, and cover crops can reduce nutrient influx during runoff events. The use of natural compost and mulch instead of chemical fertilizers can also help contain nutrients and reduce their impact on water systems.

In summary, nutrient runoff from coastal development is a critical issue that requires immediate attention. The increasing development along coastlines worldwide exacerbates the problem, leading to degraded water quality and stressed marine ecosystems. By understanding the sources and impacts of nutrient pollution, we can implement effective management practices and restore the health of our coastal environments.

Scallop harvesting closures

One example of scallop harvesting closures is the temporary closure of the Pasco Zone for the 2024 Regional Bay Scallop Season in Florida, USA. This closure was a precautionary measure due to the detection of saxitoxin and Pyrodinium bahamanse exceeding safety thresholds, as set out by the National Shellfish Sanitation Program.

In New Zealand, the government ordered the closure of a scallop fishery in 1980 due to a significant decline in catch numbers, with only 41 tonnes caught that year, down from 1246 tonnes in 1975. The closure allowed for scallop populations to recover, and spat seeding in the 1980s helped boost their numbers.

In the United States, scallop harvesting closures are also implemented to manage fishing efforts and boost scallop meat yield. After a period of closure, areas are reopened for scallop fishing when the scallops are larger and more suitable for harvest. This process is managed by allocating a certain number of trips to vessels with corresponding trip limits in dedicated access areas. Once the high concentrations of scallops have been fished down, the area may be closed again to protect any remaining small scallops and allow the population to rebound.

Additionally, scallop harvesting closures can be enforced due to pollution and safety concerns. For instance, the Tasman Bay area in New Zealand was closed to commercial scallop harvesting from 2009 to 2011, and again in 2015, due to a decline in scallop numbers caused by fishing, climate effects, disease, pollutants, and sediment runoff.

To ensure the sustainability of scallop populations, regulations are in place to control the harvesting methods and quantities. In New York, for instance, recreational harvesters are limited to one bushel of bay scallops per day during the season, and scallops may only be taken from areas designated by the DEC as certified or open for harvest.

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