Cormorants in the Local Marine Ecosystem
Dr. Susan Elbin from The Wildlife Trust and Mr. Colin Grubel from Queens College gave a brief presentation on the population of double-crested cormorants in New York's marine waters. Chairman Wise had invited Dr. Elbin and Mr. Grubel to address the Council because many fishermen believe that the impact of these fish-eating birds on local fish stocks is large and increasing as the abundance of these birds continues to rise in local waters. Dr. Elbin and Mr. Grubel have been conducting studies of the cormorant for the last two years. They came to the meeting to share their findings and answer any questions the Council and/or audience may have.
Dr. Elbin stated that cormorants have been federally protected since the 1960?s, when the number of cormorants in many areas of the country had been seriously reduced through food chain poisoning. They have made an impressive come-back since then. Besides the large amount of fish that cormorants eat, their droppings are high in ammonia, nitrogen and phosphates causing them to be very acidic, often killing vegetation in the nesting/roosting areas.
Since the 1980?s, cormorants in the New York Harbor (the only area in New York's marine waters for which there is any quantitative information on their abundance) has increased tremendously. There are six identified nesting island for cormorants in New York Harbor and its immediate environs. One bird eats about 1 lb of fish per day. Based on diet studies of cormorant colonies in the Great Lakes, it is estimated that a single colony of cormorants can, during the breeding season, eat 1,700 tons of fish. Based solely on Christmas Census bird counts (admittedly, not the time of year when cormorant population is at its peak in New York waters), Dr. Elbin estimates that there were approximately 4,000 adult cormorants (2,000 breeding pairs) in the New York Harbor area last year. Assuming that each breeding pair produced 2 young gives a total population of 4,000 birds.
Mr. Grubel then described preliminary results of studies on the diet of local double-crested cormorants. From examination of bolus samples (regurgitation of partially digested stomach contents), cormorants in New York Harbor appear to be opportunists. They don?t specialize in any specific type of fish; they take and eat whatever fish is available. Those species that are most widely and consistently found in their diet are cunner (bergall), scup (porgy) and American eel. Neither striped bass nor winter flounder were frequently found in the bolus samples, although they were present. Mr. Grubel cautioned that coincident studies of the species composition of local fish stocks were not undertaken at the same time as the cormorant diet studies.
Commercial fisherman Mr. John Mihale stated that he believes cormorant predation on local fish stocks is having a potentially significant on these populations. He thinks this issue should be studied more closely because he doesn?t feel that fishing hatches should be seen as the sole factor affecting the abundance of local fish species.
It was agreed by all that it would be valuable to have Dr. Elbin and Mr. Grubel continue their studies. Chairman Wise suggested he would write a letter on behalf of the council to support a proposal that Dr. Elbin will be putting together to seek further funding. Dr. Elbin?s contact information is [email protected]. She would be interested in hearing from anyone who has a suggestion how the research can be expanded and improved upon.
Page last modified Tuesday, February 27, 2007 by George E. Carroll
Dr. Susan Elbin from The Wildlife Trust and Mr. Colin Grubel from Queens College gave a brief presentation on the population of double-crested cormorants in New York's marine waters. Chairman Wise had invited Dr. Elbin and Mr. Grubel to address the Council because many fishermen believe that the impact of these fish-eating birds on local fish stocks is large and increasing as the abundance of these birds continues to rise in local waters. Dr. Elbin and Mr. Grubel have been conducting studies of the cormorant for the last two years. They came to the meeting to share their findings and answer any questions the Council and/or audience may have.
Dr. Elbin stated that cormorants have been federally protected since the 1960?s, when the number of cormorants in many areas of the country had been seriously reduced through food chain poisoning. They have made an impressive come-back since then. Besides the large amount of fish that cormorants eat, their droppings are high in ammonia, nitrogen and phosphates causing them to be very acidic, often killing vegetation in the nesting/roosting areas.
Since the 1980?s, cormorants in the New York Harbor (the only area in New York's marine waters for which there is any quantitative information on their abundance) has increased tremendously. There are six identified nesting island for cormorants in New York Harbor and its immediate environs. One bird eats about 1 lb of fish per day. Based on diet studies of cormorant colonies in the Great Lakes, it is estimated that a single colony of cormorants can, during the breeding season, eat 1,700 tons of fish. Based solely on Christmas Census bird counts (admittedly, not the time of year when cormorant population is at its peak in New York waters), Dr. Elbin estimates that there were approximately 4,000 adult cormorants (2,000 breeding pairs) in the New York Harbor area last year. Assuming that each breeding pair produced 2 young gives a total population of 4,000 birds.
Mr. Grubel then described preliminary results of studies on the diet of local double-crested cormorants. From examination of bolus samples (regurgitation of partially digested stomach contents), cormorants in New York Harbor appear to be opportunists. They don?t specialize in any specific type of fish; they take and eat whatever fish is available. Those species that are most widely and consistently found in their diet are cunner (bergall), scup (porgy) and American eel. Neither striped bass nor winter flounder were frequently found in the bolus samples, although they were present. Mr. Grubel cautioned that coincident studies of the species composition of local fish stocks were not undertaken at the same time as the cormorant diet studies.
Commercial fisherman Mr. John Mihale stated that he believes cormorant predation on local fish stocks is having a potentially significant on these populations. He thinks this issue should be studied more closely because he doesn?t feel that fishing hatches should be seen as the sole factor affecting the abundance of local fish species.
It was agreed by all that it would be valuable to have Dr. Elbin and Mr. Grubel continue their studies. Chairman Wise suggested he would write a letter on behalf of the council to support a proposal that Dr. Elbin will be putting together to seek further funding. Dr. Elbin?s contact information is [email protected]. She would be interested in hearing from anyone who has a suggestion how the research can be expanded and improved upon.
Page last modified Tuesday, February 27, 2007 by George E. Carroll
