How have humans exploited molluscs?

      The relationship between humans and molluscs dates back to the earliest records of human history, and likely even further, as primitive tribes first explored shores in search of sustenance. 

Among invertebrates, molluscs have had an unparalleled influence on human culture, second only to arthropods. 

 

Despite their abundance, many mollusc species are being harvested unsustainably for food and their ornamental shells, leading to concerns over their diminishing populations and the looming threat of extinction.

The Exploitation of Molluscs by Humans

Some of the broad means where uses were transformed into exploitation are,

1. Culinary Use: 

    Humans have relied on molluscs as a food source since prehistoric times, as evidenced by shell middens found near ancient settlements. 

Today, aquaculture presents a sustainable method for cultivating commercially valuable species like oysters and abalones. Larval stages are raised in controlled environments, with young adults later relocated to protected marine areas such as estuaries. 

The annual yield of cultured oysters reaches millions. However, many non-commercial species are still harvested indiscriminately, without any measures for their replenishment.

2. Trade and Ornamental Value: 

Bangles made from conch shell

    Mollusc shells have served as valuable trade items for millennia, with ancient trade routes identifiable through the discovery of shells far from their natural habitats, often embellished with precious metals and gems. 

Certain molluscs, like helmets (Cassia), are particularly prized for their unique colouration, which makes them ideal for cameo carving. While shell collection was once limited to those found on beaches or gathered by free divers, advancements in dredging and scuba diving have led to the exploitation of deep-sea species.

3. Shells as Currency: 

   In various cultures, shells served as a form of currency in place of metal coins. For instance, Pacific Native American tribes utilized scaphopod shells as "wampum," while the "money cowrie" was a widely accepted medium of exchange in the tropical Pacific.

4. Pearl Production: 

    Pearls are formed when a foreign object becomes trapped between the shell and the mantle of a bivalve. 

The mantle secretes layers of calcium carbonate, creating nacre (mother-of-pearl), which has light-refracting properties that result in an attractive opalescent appearance. 

Today, cultured pearls supplement the natural supply, and various molluscs that do not yield commercially valuable pearls still produce beautiful nacreous linings used in mother-of-pearl jewellery.

5. Communication Tools:      

   Giant conch shells have long served as instruments for communication among the island cultures of the Indo-Pacific. When blown into, these shells produce resonant musical tones, a practice that continues today.

6. Industrial Uses: 

   Before the advent of plastic, clam shells were utilized in the button-making industry due to their crystalline calcium carbonate properties. Their rigidity allowed for drilling without shattering, making them ideal for this purpose.

7. Ink Production : 

   The ink sacs of cuttlefish, harvested during food fishing, provided one of the earliest sources of non-fading ink for writing. 

Additionally, the internal cuttlebone has been a longstanding source of calcium for canaries and other caged birds, as it is easily broken down and digested.

8. Cultural Influence: 

    One of the most significant impacts of molluscs on human history arose from the Phoenicians, a seafaring civilization in the Mediterranean. 

They exploited the purple dye derived from the rock snail, which was used to colour fabrics a rich maroon hue known as Royal Purple. This dye was highly sought after and expensive, facilitating extensive trade networks that allowed the Phoenicians to spread elements of their culture, including the Phoenician alphabet, which remains foundational to modern Western languages.

In summary, molluscs have played a multifaceted role in human history, and thus exploited.  They influenced dietary practices, trade, culture, and even communication. Their significance continues to resonate today, highlighting the need for sustainable practices to protect these vital species.